ASP.NET+Core/LittleAspNetCoreBook.pdf.txt

Table	of	Contents

Introduction

Your	first	application

Get	the	SDK

Hello	World	in	C#

Create	an	ASP.NET	Core	project

MVC	basics

Create	a	controller

Create	models

Create	a	view

Add	a	service	class

Use	dependency	injection

Finish	the	controller

Update	the	layout

Add	external	packages

Use	a	database

Connect	to	a	database

Update	the	context

Create	a	migration

Create	a	new	service	class

Add	more	features

Add	new	to-do	items

Complete	items	with	a	checkbox

Security	and	identity

1.1

1.2

1.2.1

1.2.2

1.2.3

1.3

1.3.1

1.3.2

1.3.3

1.3.4

1.3.5

1.3.6

1.3.7

1.4

1.5

1.5.1

1.5.2

1.5.3

1.5.4

1.6

1.6.1

1.6.2

1.7

2

Require	authentication

Using	identity	in	the	application

Authorization	with	roles

More	resources

Automated	testing

Unit	testing

Integration	testing

Deploy	the	application

Deploy	to	Azure

Deploy	with	Docker

Conclusion

1.7.1

1.7.2

1.7.3

1.7.4

1.8

1.8.1

1.8.2

1.9

1.9.1

1.9.2

1.10

3

Introduction

The	Little	ASP.NET	Core	Book

by	Nate	Barbettini

Copyright	©	2018.	All	rights	reserved.

ISBN:	978-1-387-75615-5

Released	under	the	Creative	Commons	Attribution	4.0	license.	You	are

free	to	share,	copy,	and	redistribute	this	book	in	any	format,	or	remix	and

transform	it	for	any	purpose	(even	commercially).	You	must	give

appropriate	credit	and	provide	a	link	to	the	license.

For	more	information,	visit

https://creativecommons.org/licenses/by/4.0/

Introduction

Thanks	for	picking	up	The	Little	ASP.NET	Core	Book!	I	wrote	this	short

book	to	help	developers	and	people	interested	in	web	programming

learn	about	ASP.NET	Core,	a	new	framework	for	building	web

applications	and	APIs.

The	Little	ASP.NET	Core	Book	is	structured	as	a	tutorial.	You'll	build	an

application	from	start	to	finish	and	learn:

The	basics	of	the	MVC	(Model-View-Controller)	pattern

How	front-end	code	(HTML,	CSS,	JavaScript)	works	together	with

back-end	code

What	dependency	injection	is	and	why	it's	useful

How	to	read	and	write	data	to	a	database

How	to	add	log-in,	registration,	and	security

How	to	deploy	the	application	to	the	web

4

Introduction

Don't	worry,	you	don't	need	to	know	anything	about	ASP.NET	Core	(or

any	of	the	above)	to	get	started.

Before	you	begin

The	code	for	the	finished	version	of	the	application	you'll	build	is

available	on	GitHub:

https://www.github.com/nbarbettini/little-aspnetcore-todo

Feel	free	to	download	it	if	you	want	to	see	the	finished	product,	or

compare	as	you	write	your	own	code.

The	book	itself	is	updated	frequently	with	bug	fixes	and	new	content.	If

you're	reading	a	PDF,	e-book,	or	print	version,	check	the	official	website

(littleasp.net/book)	to	see	if	there's	an	updated	version	available.	The

very	last	page	of	the	book	contains	version	information	and	a	changelog.

Reading	in	your	own	language

Thanks	to	some	fantastic	multilingual	contributors,	the	Little	ASP.NET

Core	Book	has	been	translated	into	other	languages:

Turkish:	https://sahinyanlik.gitbooks.io/kisa-asp-net-core-kitabi/

Chinese:	https://windsting.github.io/little-aspnetcore-book/book/

Who	this	book	is	for

If	you're	new	to	programming,	this	book	will	introduce	you	to	the

patterns	and	concepts	used	to	build	modern	web	applications.	You'll

learn	how	to	build	a	web	app	(and	how	the	big	pieces	fit	together)	by

5

Introduction

building	something	from	scratch!	While	this	little	book	won't	be	able	to

cover	absolutely	everything	you	need	to	know	about	programming,	it'll

give	you	a	starting	point	so	you	can	learn	more	advanced	topics.

If	you	already	code	in	a	backend	language	like	Node,	Python,	Ruby,	Go,

or	Java,	you'll	notice	a	lot	of	familiar	ideas	like	MVC,	view	templates,	and

dependency	injection.	The	code	will	be	in	C#,	but	it	won't	look	too

different	from	what	you	already	know.

If	you're	an	ASP.NET	MVC	developer,	you'll	feel	right	at	home!	ASP.NET

Core	adds	some	new	tools	and	reuses	(and	simplifies)	the	things	you

already	know.	I'll	point	out	some	of	the	differences	below.

No	matter	what	your	previous	experience	with	web	programming,	this

book	will	teach	you	everything	you	need	to	create	a	simple	and	useful

web	application	in	ASP.NET	Core.	You'll	learn	how	to	build	functionality

using	backend	and	frontend	code,	how	to	interact	with	a	database,	and

how	to	deploy	the	app	to	the	world.

What	is	ASP.NET	Core?

ASP.NET	Core	is	a	web	framework	created	by	Microsoft	for	building	web

applications,	APIs,	and	microservices.	It	uses	common	patterns	like	MVC

(Model-View-Controller),	dependency	injection,	and	a	request	pipeline

comprised	of	middleware.	It's	open-source	under	the	Apache	2.0	license,

which	means	the	source	code	is	freely	available,	and	the	community	is

encouraged	to	contribute	bug	fixes	and	new	features.

ASP.NET	Core	runs	on	top	of	Microsoft's	.NET	runtime,	similar	to	the

Java	Virtual	Machine	(JVM)	or	the	Ruby	interpreter.	You	can	write

ASP.NET	Core	applications	in	a	number	of	languages	(C#,	Visual	Basic,

F#).	C#	is	the	most	popular	choice,	and	it's	what	I'll	use	in	this	book.	You

can	build	and	run	ASP.NET	Core	applications	on	Windows,	Mac,	and

Linux.

6

Introduction

Why	do	we	need	another	web
framework?

There	are	a	lot	of	great	web	frameworks	to	choose	from	already:

Node/Express,	Spring,	Ruby	on	Rails,	Django,	Laravel,	and	many	more.

What	advantages	does	ASP.NET	Core	have?

Speed.	ASP.NET	Core	is	fast.	Because	.NET	code	is	compiled,	it

executes	much	faster	than	code	in	interpreted	languages	like

JavaScript	or	Ruby.	ASP.NET	Core	is	also	optimized	for

multithreading	and	asynchronous	tasks.	It's	common	to	see	a	5-10x

speed	improvement	over	code	written	in	Node.js.

Ecosystem.	ASP.NET	Core	may	be	new,	but	.NET	has	been	around

for	a	long	time.	There	are	thousands	of	packages	available	on	NuGet

(the	.NET	package	manager;	think	npm,	Ruby	gems,	or	Maven).

There	are	already	packages	available	for	JSON	deserialization,

database	connectors,	PDF	generation,	or	almost	anything	else	you

can	think	of.

Security.	The	team	at	Microsoft	takes	security	seriously,	and

ASP.NET	Core	is	built	to	be	secure	from	the	ground	up.	It	handles

things	like	sanitizing	input	data	and	preventing	cross-site	request

forgery	(CSRF)	attacks,	so	you	don't	have	to.	You	also	get	the

benefit	of	static	typing	with	the	.NET	compiler,	which	is	like	having	a

very	paranoid	linter	turned	on	at	all	times.	This	makes	it	harder	to	do

something	you	didn't	intend	with	a	variable	or	chunk	of	data.

.NET	Core	and	.NET	Standard

Throughout	this	book,	you'll	be	learning	about	ASP.NET	Core	(the	web

framework).	I'll	occasionally	mention	the	.NET	runtime,	the	supporting

library	that	runs	.NET	code.	If	this	already	sounds	like	Greek	to	you,	just

7

Introduction

skip	to	the	next	chapter!

You	may	also	hear	about	.NET	Core	and	.NET	Standard.	The	naming	gets

confusing,	so	here's	a	simple	explanation:

.NET	Standard	is	a	platform-agnostic	interface	that	defines	features	and

APIs.	It's	important	to	note	that	.NET	Standard	doesn't	represent	any

actual	code	or	functionality,	just	the	API	definition.	There	are	different

"versions"	or	levels	of	.NET	Standard	that	reflect	how	many	APIs	are

available	(or	how	wide	the	API	surface	area	is).	For	example,	.NET

Standard	2.0	has	more	APIs	available	than	.NET	Standard	1.5,	which	has

more	APIs	than	.NET	Standard	1.0.

.NET	Core	is	the	.NET	runtime	that	can	be	installed	on	Windows,	Mac,	or

Linux.	It	implements	the	APIs	defined	in	the	.NET	Standard	interface	with

the	appropriate	platform-specific	code	on	each	operating	system.	This	is

what	you'll	install	on	your	own	machine	to	build	and	run	ASP.NET	Core

applications.

And	just	for	good	measure,	.NET	Framework	is	a	different

implementation	of	.NET	Standard	that	is	Windows-only.	This	was	the

only	.NET	runtime	until	.NET	Core	came	along	and	brought	.NET	to	Mac

and	Linux.	ASP.NET	Core	can	also	run	on	Windows-only	.NET

Framework,	but	I	won't	touch	on	this	too	much.

If	you're	confused	by	all	this	naming,	no	worries!	We'll	get	to	some	real

code	in	a	bit.

A	note	to	ASP.NET	4	developers

If	you	haven't	used	a	previous	version	of	ASP.NET,	skip	ahead	to	the

next	chapter.

8

Introduction

ASP.NET	Core	is	a	complete	ground-up	rewrite	of	ASP.NET,	with	a	focus

on	modernizing	the	framework	and	finally	decoupling	it	from

System.Web,	IIS,	and	Windows.	If	you	remember	all	the	OWIN/Katana

stuff	from	ASP.NET	4,	you're	already	halfway	there:	the	Katana	project

became	ASP.NET	5	which	was	ultimately	renamed	to	ASP.NET	Core.

Because	of	the	Katana	legacy,	the	 	Startup		class	is	front	and	center,	and

there's	no	more	 	Application_Start		or	 	Global.asax	.	The	entire	pipeline

is	driven	by	middleware,	and	there's	no	longer	a	split	between	MVC	and

Web	API:	controllers	can	simply	return	views,	status	codes,	or	data.

Dependency	injection	comes	baked	in,	so	you	don't	need	to	install	and

configure	a	container	like	StructureMap	or	Ninject	if	you	don't	want	to.

And	the	entire	framework	has	been	optimized	for	speed	and	runtime

efficiency.

Alright,	enough	introduction.	Let's	dive	in	to	ASP.NET	Core!

9

Your	first	application

Your	first	application

Ready	to	build	your	first	web	app	with	ASP.NET	Core?	You'll	need	to

gather	a	few	things	first:

Your	favorite	code	editor.	You	can	use	Atom,	Sublime,	Notepad,	or

whatever	editor	you	prefer	writing	code	in.	If	you	don't	have	a	favorite,

give	Visual	Studio	Code	a	try.	It's	a	free,	cross-platform	code	editor	that

has	rich	support	for	writing	C#,	JavaScript,	HTML,	and	more.	Just	search

for	"download	visual	studio	code"	and	follow	the	instructions.

If	you're	on	Windows,	you	can	also	use	Visual	Studio	to	build	ASP.NET

Core	applications.	You'll	need	Visual	Studio	2017	version	15.3	or	later

(the	free	Community	Edition	is	fine).	Visual	Studio	has	great	code

completion	and	refactoring	support	for	C#,	although	Visual	Studio	Code

is	close	behind.

The	.NET	Core	SDK.	Regardless	of	the	editor	or	platform	you're	using,

you'll	need	to	install	the	.NET	Core	SDK,	which	includes	the	runtime,

base	libraries,	and	command	line	tools	you	need	for	building	ASP.NET

Core	applications.	The	SDK	can	be	installed	on	Windows,	Mac,	or	Linux.

Once	you've	decided	on	an	editor,	you'll	need	to	get	the	SDK.

10

Get	the	SDK

Get	the	SDK

Search	for	"download	.net	core"	and	follow	the	instructions	on

Microsoft's	download	page	to	get	the	.NET	Core	SDK.	After	the	SDK	has

finished	installing,	open	up	the	Terminal	(or	PowerShell	on	Windows)	and

use	the	 	dotnet		command	line	tool	(also	called	a	CLI)	to	make	sure

everything	is	working:

dotnet	--version

2.1.104

You	can	get	more	information	about	your	platform	with	the	 	--info		flag:

dotnet	--info

.NET	Command	Line	Tools	(2.1.104)

Product	Information:

	Version:												2.1.104

	Commit	SHA-1	hash:		48ec687460

Runtime	Environment:

	OS	Name:					Mac	OS	X

	OS	Version:		10.13

(more	details...)

If	you	see	output	like	the	above,	you're	ready	to	go!

11

Hello	World	in	C#

Hello	World	in	C#

Before	you	dive	into	ASP.NET	Core,	try	creating	and	running	a	simple	C#

application.

You	can	do	this	all	from	the	command	line.	First,	open	up	the	Terminal

(or	PowerShell	on	Windows).	Navigate	to	the	location	you	want	to	store

your	projects,	such	as	your	Documents	directory:

cd	Documents

Use	the	 	dotnet		command	to	create	a	new	project:

dotnet	new	console	-o	CsharpHelloWorld

The	 	dotnet	new		command	creates	a	new	.NET	project	in	C#	by	default.

The	 	console		parameter	selects	a	template	for	a	console	application	(a

program	that	outputs	text	to	the	screen).	The	 	-o	CsharpHelloWorld	

parameter	tells	 	dotnet	new		to	create	a	new	directory	called

	CsharpHelloWorld		for	all	the	project	files.	Move	into	this	new	directory:

cd	CsharpHelloWorld

	dotnet	new	console		creates	a	basic	C#	program	that	writes	the	text

	Hello	World!		to	the	screen.	The	program	is	comprised	of	two	files:	a

project	file	(with	a	 	.csproj		extension)	and	a	C#	code	file	(with	a	 	.cs	

extension).	If	you	open	the	former	in	a	text	or	code	editor,	you'll	see	this:

CsharpHelloWorld.csproj

<Project	Sdk="Microsoft.NET.Sdk">

12

Hello	World	in	C#

		<PropertyGroup>

				<OutputType>Exe</OutputType>

				<TargetFramework>netcoreapp2.0</TargetFramework>

		</PropertyGroup>

</Project>

The	project	file	is	XML-based	and	defines	some	metadata	about	the

project.	Later,	when	you	reference	other	packages,	those	will	be	listed

here	(similar	to	a	 	package.json		file	for	npm).	You	won't	have	to	edit	this

file	by	hand	very	often.

Program.cs

using	System;

namespace	CsharpHelloWorld

{

				class	Program

				{

								static	void	Main(string[]	args)

								{

												Console.WriteLine("Hello	World!");

								}

				}

}

	static	void	Main		is	the	entry	point	method	of	a	C#	program,	and	by

convention	it's	placed	in	a	class	(a	type	of	code	structure	or	module)

called	 	Program	.	The	 	using		statement	at	the	top	imports	the	built-in

	System		classes	from	.NET	and	makes	them	available	to	the	code	in	your

class.

From	inside	the	project	directory,	use	 	dotnet	run		to	run	the	program.

You'll	see	the	output	written	to	the	console	after	the	code	compiles:

dotnet	run

13

Hello	World	in	C#

Hello	World!

That's	all	it	takes	to	scaffold	and	run	a	.NET	program!	Next,	you'll	do	the

same	thing	for	an	ASP.NET	Core	application.

14

Create	an	ASP.NET	Core	project

Create	an	ASP.NET	Core	project

If	you're	still	in	the	directory	you	created	for	the	Hello	World	sample,

move	back	up	to	your	Documents	or	home	directory:

cd	..

Next,	create	a	new	directory	to	store	your	entire	project,	and	move	into

it:

mkdir	AspNetCoreTodo

cd	AspNetCoreTodo

Next,	create	a	new	project	with	 	dotnet	new	,	this	time	with	some	extra

options:

dotnet	new	mvc	--auth	Individual	-o	AspNetCoreTodo

cd	AspNetCoreTodo

This	creates	a	new	project	from	the	 	mvc		template,	and	adds	some

additional	authentication	and	security	bits	to	the	project.	(I'll	cover

security	in	the	Security	and	identity	chapter.)

You	might	be	wondering	why	you	have	a	directory	called

	AspNetCoreTodo		inside	another	directory	called	 	AspNetCoreTodo	.

The	top-level	or	"root"	directory	can	contain	one	or	more	project

directories.	The	root	directory	is	sometimes	called	a	solution

directory.	Later,	you'll	add	more	project	directories	side-by-side

with	the	 	AspNetCoreTodo		project	directory,	all	within	a	single	root

solution	directory.

15

Create	an	ASP.NET	Core	project

You'll	see	quite	a	few	files	show	up	in	the	new	project	directory.	Once

you	 	cd		into	the	new	directory,	all	you	have	to	do	is	run	the	project:

dotnet	run

Now	listening	on:	http://localhost:5000

Application	started.	Press	Ctrl+C	to	shut	down.

Instead	of	printing	to	the	console	and	exiting,	this	program	starts	a	web

server	and	waits	for	requests	on	port	5000.

Open	your	web	browser	and	navigate	to	 	http://localhost:5000	.	You'll

see	the	default	ASP.NET	Core	splash	page,	which	means	your	project	is

working!	When	you're	done,	press	Ctrl-C	in	the	terminal	window	to	stop

the	server.

The	parts	of	an	ASP.NET	Core	project

The	 	dotnet	new	mvc		template	generates	a	number	of	files	and

directories	for	you.	Here	are	the	most	important	things	you	get	out	of

the	box:

The	Program.cs	and	Startup.cs	files	set	up	the	web	server	and

ASP.NET	Core	pipeline.	The	 	Startup		class	is	where	you	can	add

middleware	that	handles	and	modifies	incoming	requests,	and	serves

things	like	static	content	or	error	pages.	It's	also	where	you	add	your

own	services	to	the	dependency	injection	container	(more	on	this

later).

The	Models,	Views,	and	Controllers	directories	contain	the

components	of	the	Model-View-Controller	(MVC)	architecture.

You'll	explore	all	three	in	the	next	chapter.

16

Create	an	ASP.NET	Core	project

The	wwwroot	directory	contains	static	assets	like	CSS,	JavaScript,

and	image	files.	Files	in	 	wwwroot		will	be	served	as	static	content,

and	can	be	bundled	and	minified	automatically.

The	appsettings.json	file	contains	configuration	settings	ASP.NET

Core	will	load	on	startup.	You	can	use	this	to	store	database

connection	strings	or	other	things	that	you	don't	want	to	hard-code.

Tips	for	Visual	Studio	Code

If	you're	using	Visual	Studio	Code	for	the	first	time,	here	are	a	couple	of

helpful	tips	to	get	you	started:

Open	the	project	root	folder:	In	Visual	Studio	Code,	choose	File	-

Open	or	File	-	Open	Folder.	Open	the	 	AspNetCoreTodo		folder	(the

root	directory),	not	the	inner	project	directory.	If	Visual	Studio	Code

prompts	you	to	install	missing	files,	click	Yes	to	add	them.

F5	to	run	(and	debug	breakpoints):	With	your	project	open,	press	F5

to	run	the	project	in	debug	mode.	This	is	the	same	as	 	dotnet	run	

on	the	command	line,	but	you	have	the	benefit	of	setting

breakpoints	in	your	code	by	clicking	on	the	left	margin:

Lightbulb	to	fix	problems:	If	your	code	contains	red	squiggles

(compiler	errors),	put	your	cursor	on	the	code	that's	red	and	look	for

the	lightbulb	icon	on	the	left	margin.	The	lightbulb	menu	will	suggest

17

Create	an	ASP.NET	Core	project

common	fixes,	like	adding	a	missing	 	using		statement	to	your	code:

Compile	quickly:	Use	the	shortcut	 	Command-Shift-B		or	 	Control-

Shift-B		to	run	the	Build	task,	which	does	the	same	thing	as	 	dotnet

build	.

These	tips	apply	to	Visual	Studio	(not	Code)	on	Windows	too.	If

you're	using	Visual	Studio,	you'll	need	to	open	the	 	.csproj	

project	file	directly.	Visual	Studio	will	later	prompt	you	to	save	the

Solution	file,	which	you	should	save	in	the	root	directory	(the	first

	AspNetCoreTodo		folder).	You	can	also	create	an	ASP.NET	Core

project	directly	within	Visual	Studio	using	the	templates	in	File	-

New	Project.

A	note	about	Git

If	you	use	Git	or	GitHub	to	manage	your	source	code,	now	is	a	good	time

to	do	 	git	init		and	initialize	a	Git	repository	in	the	project	root

directory:

cd	..

git	init

Make	sure	you	add	a	 	.gitignore		file	that	ignores	the	 	bin		and	 	obj	

directories.	The	Visual	Studio	template	on	GitHub's	gitignore	template

repo	(https://github.com/github/gitignore)	works	great.

18

Create	an	ASP.NET	Core	project

There's	plenty	more	to	explore,	so	let's	dive	in	and	start	building	an

application!

19

MVC	basics

MVC	basics

In	this	chapter,	you'll	explore	the	MVC	system	in	ASP.NET	Core.	MVC

(Model-View-Controller)	is	a	pattern	for	building	web	applications	that's

used	in	almost	every	web	framework	(Ruby	on	Rails	and	Express	are

popular	examples),	plus	frontend	JavaScript	frameworks	like	Angular.

Mobile	apps	on	iOS	and	Android	use	a	variation	of	MVC	as	well.

As	the	name	suggests,	MVC	has	three	components:	models,	views,	and

controllers.	Controllers	handle	incoming	requests	from	a	client	or	web

browser	and	make	decisions	about	what	code	to	run.	Views	are

templates	(usually	HTML	plus	a	templating	language	like	Handlebars,

Pug,	or	Razor)	that	get	data	added	to	them	and	then	are	displayed	to	the

user.	Models	hold	the	data	that	is	added	to	views,	or	data	that	is	entered

by	the	user.

A	common	pattern	for	MVC	code	is:

The	controller	receives	a	request	and	looks	up	some	information	in	a

database

The	controller	creates	a	model	with	the	information	and	attaches	it

to	a	view

The	view	is	rendered	and	displayed	in	the	user's	browser

The	user	clicks	a	button	or	submits	a	form,	which	sends	a	new

request	to	the	controller,	and	the	cycle	repeats

If	you've	worked	with	MVC	in	other	languages,	you'll	feel	right	at	home

in	ASP.NET	Core	MVC.	If	you're	new	to	MVC,	this	chapter	will	teach	you

the	basics	and	will	help	get	you	started.

What	you'll	build

20

MVC	basics

The	"Hello	World"	exercise	of	MVC	is	building	a	to-do	list	application.	It's

a	great	project	since	it's	small	and	simple	in	scope,	but	it	touches	each

part	of	MVC	and	covers	many	of	the	concepts	you'd	use	in	a	larger

application.

In	this	book,	you'll	build	a	to-do	app	that	lets	the	user	add	items	to	their

to-do	list	and	check	them	off	once	complete.	More	specifically,	you'll	be

creating:

A	web	application	server	(sometimes	called	the	"backend")	using

ASP.NET	Core,	C#,	and	the	MVC	pattern

A	database	to	store	the	user's	to-do	items	using	the	SQLite	database

engine	and	a	system	called	Entity	Framework	Core

Web	pages	and	an	interface	that	the	user	will	interact	with	via	their

browser,	using	HTML,	CSS,	and	JavaScript	(called	the	"frontend")

A	login	form	and	security	checks	so	each	user's	to-do	list	is	kept

private

Sound	good?	Let's	built	it!	If	you	haven't	already	created	a	new	ASP.NET

Core	project	using	 	dotnet	new	mvc	,	follow	the	steps	in	the	previous

chapter.	You	should	be	able	to	build	and	run	the	project	and	see	the

default	welcome	screen.

21

Create	a	controller

Create	a	controller

There	are	already	a	few	controllers	in	the	project's	Controllers	directory,

including	the	 	HomeController		that	renders	the	default	welcome	screen

you	see	when	you	visit	 	http://localhost:5000	.	You	can	ignore	these

controllers	for	now.

Create	a	new	controller	for	the	to-do	list	functionality,	called

	TodoController	,	and	add	the	following	code:

Controllers/TodoController.cs

using	System;

using	System.Collections.Generic;

using	System.Linq;

using	System.Threading.Tasks;

using	Microsoft.AspNetCore.Mvc;

namespace	AspNetCoreTodo.Controllers

{

				public	class	TodoController	:	Controller

				{

								//	Actions	go	here

				}

}

Routes	that	are	handled	by	controllers	are	called	actions,	and	are

represented	by	methods	in	the	controller	class.	For	example,	the

	HomeController		includes	three	action	methods	( 	Index	,	 	About	,	and

	Contact	)	which	are	mapped	by	ASP.NET	Core	to	these	route	URLs:

localhost:5000/Home									->	Index()

localhost:5000/Home/About			->	About()

localhost:5000/Home/Contact	->	Contact()

22

Create	a	controller

There	are	a	number	of	conventions	(common	patterns)	used	by	ASP.NET

Core,	such	as	the	pattern	that	 	FooController		becomes	 	/Foo	,	and	the

	Index		action	name	can	be	left	out	of	the	URL.	You	can	customize	this

behavior	if	you'd	like,	but	for	now,	we'll	stick	to	the	default	conventions.

Add	a	new	action	called	 	Index		to	the	 	TodoController	,	replacing	the	 	//

Actions	go	here		comment:

public	class	TodoController	:	Controller

{

				public	IActionResult	Index()

				{

								//	Get	to-do	items	from	database

								//	Put	items	into	a	model

								//	Render	view	using	the	model

				}

}

Action	methods	can	return	views,	JSON	data,	or	HTTP	status	codes	like

	200	OK		and	 	404	Not	Found	.	The	 	IActionResult		return	type	gives	you

the	flexibility	to	return	any	of	these	from	the	action.

It's	a	best	practice	to	keep	controllers	as	lightweight	as	possible.	In	this

case,	the	controller	will	be	responsible	for	getting	the	to-do	items	from

the	database,	putting	those	items	into	a	model	the	view	can	understand,

and	sending	the	view	back	to	the	user's	browser.

Before	you	can	write	the	rest	of	the	controller	code,	you	need	to	create	a

model	and	a	view.

23

Create	models

Create	models

There	are	two	separate	model	classes	that	need	to	be	created:	a	model

that	represents	a	to-do	item	stored	in	the	database	(sometimes	called	an

entity),	and	the	model	that	will	be	combined	with	a	view	(the	MV	in

MVC)	and	sent	back	to	the	user's	browser.	Because	both	of	them	can	be

referred	to	as	"models",	I'll	refer	to	the	latter	as	a	view	model.

First,	create	a	class	called	 	TodoItem		in	the	Models	directory:

Models/TodoItem.cs

using	System;

using	System.ComponentModel.DataAnnotations;

namespace	AspNetCoreTodo.Models

{

				public	class	TodoItem

				{

								public	Guid	Id	{	get;	set;	}

								public	bool	IsDone	{	get;	set;	}

								[Required]

								public	string	Title	{	get;	set;	}

								public	DateTimeOffset?	DueAt	{	get;	set;	}

				}

}

This	class	defines	what	the	database	will	need	to	store	for	each	to-do

item:	an	ID,	a	title	or	name,	whether	the	item	is	complete,	and	what	the

due	date	is.	Each	line	defines	a	property	of	the	class:

24

Create	models

The	Id	property	is	a	guid,	or	a	globally	unique	identifier.	Guids	(or

GUIDs)	are	long	strings	of	letters	and	numbers,	like	 	43ec09f2-7f70-

4f4b-9559-65011d5781bb	.	Because	guids	are	random	and	are

extremely	unlikely	to	be	accidentally	duplicated,	they	are	commonly

used	as	unique	IDs.	You	could	also	use	a	number	(integer)	as	a

database	entity	ID,	but	you'd	need	to	configure	your	database	to

always	increment	the	number	when	new	rows	are	added	to	the

database.	Guids	are	generated	randomly,	so	you	don't	have	to	worry

about	auto-incrementing.

The	IsDone	property	is	a	boolean	(true/false	value).	By	default,	it

will	be	 	false		for	all	new	items.	Later	you'll	use	write	code	to	switch

this	property	to	 	true		when	the	user	clicks	an	item's	checkbox	in

the	view.

The	Title	property	is	a	string	(text	value).	This	will	hold	the	name	or

description	of	the	to-do	item.	The	 	[Required]		attribute	tells

ASP.NET	Core	that	this	string	can't	be	null	or	empty.

The	DueAt	property	is	a	 	DateTimeOffset	,	which	is	a	C#	type	that

stores	a	date/time	stamp	along	with	a	timezone	offset	from	UTC.

Storing	the	date,	time,	and	timezone	offset	together	makes	it	easy	to

render	dates	accurately	on	systems	in	different	timezones.

Notice	the	 	?		question	mark	after	the	 	DateTimeOffset		type?	That	marks

the	DueAt	property	as	nullable,	or	optional.	If	the	 	?		wasn't	included,

every	to-do	item	would	need	to	have	a	due	date.	The	 	Id		and	 	IsDone	

properties	aren't	marked	as	nullable,	so	they	are	required	and	will	always

have	a	value	(or	a	default	value).

Strings	in	C#	are	always	nullable,	so	there's	no	need	to	mark	the

Title	property	as	nullable.	C#	strings	can	be	null,	empty,	or	contain

text.

25

Create	models

Each	property	is	followed	by	 	get;	set;	,	which	is	a	shorthand	way	of

saying	the	property	is	read/write	(or,	more	technically,	it	has	a	getter	and

setter	methods).

At	this	point,	it	doesn't	matter	what	the	underlying	database	technology

is.	It	could	be	SQL	Server,	MySQL,	MongoDB,	Redis,	or	something	more

exotic.	This	model	defines	what	the	database	row	or	entry	will	look	like

in	C#	so	you	don't	have	to	worry	about	the	low-level	database	stuff	in

your	code.	This	simple	style	of	model	is	sometimes	called	a	"plain	old	C#

object"	or	POCO.

The	view	model

Often,	the	model	(entity)	you	store	in	the	database	is	similar	but	not

exactly	the	same	as	the	model	you	want	to	use	in	MVC	(the	view	model).

In	this	case,	the	 	TodoItem		model	represents	a	single	item	in	the

database,	but	the	view	might	need	to	display	two,	ten,	or	a	hundred	to-

do	items	(depending	on	how	badly	the	user	is	procrastinating).

Because	of	this,	the	view	model	should	be	a	separate	class	that	holds	an

array	of	 	TodoItem	s:

Models/TodoViewModel.cs

namespace	AspNetCoreTodo.Models

{

				public	class	TodoViewModel

				{

								public	TodoItem[]	Items	{	get;	set;	}

				}

}

Now	that	you	have	some	models,	it's	time	to	create	a	view	that	will	take

a	 	TodoViewModel		and	render	the	right	HTML	to	show	the	user	their	to-

do	list.

26

Create	models

27

Create	a	view

Create	a	view

Views	in	ASP.NET	Core	are	built	using	the	Razor	templating	language,

which	combines	HTML	and	C#	code.	(If	you've	written	pages	using

Handlebars	moustaches,	ERB	in	Ruby	on	Rails,	or	Thymeleaf	in	Java,

you've	already	got	the	basic	idea.)

Most	view	code	is	just	HTML,	with	the	occasional	C#	statement	added	in

to	pull	data	out	of	the	view	model	and	turn	it	into	text	or	HTML.	The	C#

statements	are	prefixed	with	the	 	@		symbol.

The	view	rendered	by	the	 	Index		action	of	the	 	TodoController		needs	to

take	the	data	in	the	view	model	(a	sequence	of	to-do	items)	and	display	it

in	a	nice	table	for	the	user.	By	convention,	views	are	placed	in	the

	Views		directory,	in	a	subdirectory	corresponding	to	the	controller	name.

The	file	name	of	the	view	is	the	name	of	the	action	with	a	 	.cshtml	

extension.

Create	a	 	Todo		directory	inside	the	 	Views		directory,	and	add	this	file:

Views/Todo/Index.cshtml

@model	TodoViewModel

@{

				ViewData["Title"]	=	"Manage	your	todo	list";

}

<div	class="panel	panel-default	todo-panel">

		<div	class="panel-heading">@ViewData["Title"]</div>

		<table	class="table	table-hover">

						<thead>

										<tr>

														<td>&#x2714;</td>

														<td>Item</td>

														<td>Due</td>

28

Create	a	view

										</tr>

						</thead>

						@foreach	(var	item	in	Model.Items)

						{

										<tr>

														<td>

																<input	type="checkbox"	class="done-checkbox">

														</td>

														<td>@item.Title</td>

														<td>@item.DueAt</td>

										</tr>

						}

		</table>

		<div	class="panel-footer	add-item-form">

				<!--	TODO:	Add	item	form	-->

		</div>

</div>

At	the	very	top	of	the	file,	the	 	@model		directive	tells	Razor	which	model

to	expect	this	view	to	be	bound	to.	The	model	is	accessed	through	the

	Model		property.

Assuming	there	are	any	to-do	items	in	 	Model.Items	,	the	 	foreach	

statement	will	loop	over	each	to-do	item	and	render	a	table	row	( 	<tr>	

element)	containing	the	item's	name	and	due	date.	A	checkbox	is	also

rendered	that	will	let	the	user	mark	the	item	as	complete.

The	layout	file

You	might	be	wondering	where	the	rest	of	the	HTML	is:	what	about	the

	<body>		tag,	or	the	header	and	footer	of	the	page?	ASP.NET	Core	uses	a

layout	view	that	defines	the	base	structure	that	every	other	view	is

rendered	inside	of.	It's	stored	in	 	Views/Shared/_Layout.cshtml	.

29

Create	a	view

The	default	ASP.NET	Core	template	includes	Bootstrap	and	jQuery	in

this	layout	file,	so	you	can	quickly	create	a	web	application.	Of	course,

you	can	use	your	own	CSS	and	JavaScript	libraries	if	you'd	like.

Customizing	the	stylesheet

The	default	template	also	includes	a	stylesheet	with	some	basic	CSS

rules.	The	stylesheet	is	stored	in	the	 	wwwroot/css		directory.	Add	a	few

new	CSS	style	rules	to	the	bottom	of	the	 	site.css		file:

wwwroot/css/site.css

div.todo-panel	{

		margin-top:	15px;

}

table	tr.done	{

		text-decoration:	line-through;

		color:	#888;

}

You	can	use	CSS	rules	like	these	to	completely	customize	how	your

pages	look	and	feel.

ASP.NET	Core	and	Razor	can	do	much	more,	such	as	partial	views	and

server-rendered	view	components,	but	a	simple	layout	and	view	is	all

you	need	for	now.	The	official	ASP.NET	Core	documentation	(at

https://docs.asp.net)	contains	a	number	of	examples	if	you'd	like	to	learn

more.

30

Add	a	service	class

Add	a	service	class

You've	created	a	model,	a	view,	and	a	controller.	Before	you	use	the

model	and	view	in	the	controller,	you	also	need	to	write	code	that	will

get	the	user's	to-do	items	from	a	database.

You	could	write	this	database	code	directly	in	the	controller,	but	it's	a

better	practice	to	keep	your	code	separate.	Why?	In	a	big,	real-world

application,	you'll	have	to	juggle	many	concerns:

Rendering	views	and	handling	incoming	data:	this	is	what	your

controller	already	does.

Performing	business	logic,	or	code	and	logic	that's	related	to	the

purpose	and	"business"	of	your	application.	In	a	to-do	list

application,	business	logic	means	decisions	like	setting	a	default	due

date	on	new	tasks,	or	only	displaying	tasks	that	are	incomplete.

Other	examples	of	business	logic	include	calculating	a	total	cost

based	on	product	prices	and	tax	rates,	or	checking	whether	a	player

has	enough	points	to	level	up	in	a	game.

Saving	and	retrieving	items	from	a	database.

Again,	it's	possible	to	do	all	of	these	things	in	a	single,	massive	controller,

but	that	quickly	becomes	too	hard	to	manage	and	test.	Instead,	it's

common	to	see	applications	split	up	into	two,	three,	or	more	"layers"	or

tiers	that	each	handle	one	(and	only	one)	concern.	This	helps	keep	the

controllers	as	simple	as	possible,	and	makes	it	easier	to	test	and	change

the	business	logic	and	database	code	later.

Separating	your	application	this	way	is	sometimes	called	a	multi-tier	or

n-tier	architecture.	In	some	cases,	the	tiers	(layers)	are	isolated	in

completely	separate	projects,	but	other	times	it	just	refers	to	how	the

31

Add	a	service	class

classes	are	organized	and	used.	The	important	thing	is	thinking	about

how	to	split	your	application	into	manageable	pieces,	and	avoid	having

controllers	or	bloated	classes	that	try	to	do	everything.

For	this	project,	you'll	use	two	application	layers:	a	presentation	layer

made	up	of	the	controllers	and	views	that	interact	with	the	user,	and	a

service	layer	that	contains	business	logic	and	database	code.	The

presentation	layer	already	exists,	so	the	next	step	is	to	build	a	service

that	handles	to-do	business	logic	and	saves	to-do	items	to	a	database.

Most	larger	projects	use	a	3-tier	architecture:	a	presentation	layer,

a	service	logic	layer,	and	a	data	repository	layer.	A	repository	is	a

class	that's	only	focused	on	database	code	(no	business	logic).	In

this	application,	you'll	combine	these	into	a	single	service	layer	for

simplicity,	but	feel	free	to	experiment	with	different	ways	of

architecting	the	code.

Create	an	interface

The	C#	language	includes	the	concept	of	interfaces,	where	the	definition

of	an	object's	methods	and	properties	is	separate	from	the	class	that

actually	contains	the	code	for	those	methods	and	properties.	Interfaces

make	it	easy	to	keep	your	classes	decoupled	and	easy	to	test,	as	you'll

see	here	(and	later	in	the	Automated	testing	chapter).	You'll	use	an

interface	to	represent	the	service	that	can	interact	with	to-do	items	in

the	database.

By	convention,	interfaces	are	prefixed	with	"I".	Create	a	new	file	in	the

Services	directory:

Services/ITodoItemService.cs

using	System;

using	System.Collections.Generic;

using	System.Threading.Tasks;

using	AspNetCoreTodo.Models;

32

Add	a	service	class

namespace	AspNetCoreTodo.Services

{

				public	interface	ITodoItemService

				{

								Task<TodoItem[]>	GetIncompleteItemsAsync();

				}

}

Note	that	the	namespace	of	this	file	is	 	AspNetCoreTodo.Services	.

Namespaces	are	a	way	to	organize	.NET	code	files,	and	it's	customary	for

the	namespace	to	follow	the	directory	the	file	is	stored	in

( 	AspNetCoreTodo.Services		for	files	in	the	 	Services		directory,	and	so	on).

Because	this	file	(in	the	 	AspNetCoreTodo.Services		namespace)	references

the	 	TodoItem		class	(in	the	 	AspNetCoreTodo.Models		namespace),	it	needs

to	include	a	 	using		statement	at	the	top	of	the	file	to	import	that

namespace.	Without	the	 	using		statement,	you'll	see	an	error	like:

The	type	or	namespace	name	'TodoItem'	could	not	be	found	(are	you	

missing	a	using	directive	or	an	assembly	reference?)

Since	this	is	an	interface,	there	isn't	any	actual	code	here,	just	the

definition	(or	method	signature)	of	the	 	GetIncompleteItemsAsync	

method.	This	method	requires	no	parameters	and	returns	a

	Task<TodoItem[]>	.

If	this	syntax	looks	confusing,	think:	"a	Task	that	contains	an	array

of	TodoItems".

The	 	Task		type	is	similar	to	a	future	or	a	promise,	and	it's	used	here

because	this	method	will	be	asynchronous.	In	other	words,	the	method

may	not	be	able	to	return	the	list	of	to-do	items	right	away	because	it

needs	to	go	talk	to	the	database	first.	(More	on	this	later.)

Create	the	service	class

33

Add	a	service	class

Now	that	the	interface	is	defined,	you're	ready	to	create	the	actual

service	class.	I'll	cover	database	code	in	depth	in	the	Use	a	database

chapter,	so	for	now	you'll	just	fake	it	and	always	return	two	hard-coded

items:

Services/FakeTodoItemService.cs

using	System;

using	System.Collections.Generic;

using	System.Threading.Tasks;

using	AspNetCoreTodo.Models;

namespace	AspNetCoreTodo.Services

{

				public	class	FakeTodoItemService	:	ITodoItemService

				{

								public	Task<TodoItem[]>	GetIncompleteItemsAsync()

								{

												var	item1	=	new	TodoItem

												{

																Title	=	"Learn	ASP.NET	Core",

																DueAt	=	DateTimeOffset.Now.AddDays(1)

												};

												var	item2	=	new	TodoItem

												{

																Title	=	"Build	awesome	apps",

																DueAt	=	DateTimeOffset.Now.AddDays(2)

												};

												return	Task.FromResult(new[]	{	item1,	item2	});

								}

				}

}

This	 	FakeTodoItemService		implements	the	 	ITodoItemService		interface

but	always	returns	the	same	array	of	two	 	TodoItem	s.	You'll	use	this	to

test	the	controller	and	view,	and	then	add	real	database	code	in	Use	a

database.

34

Add	a	service	class

35

Use	dependency	injection

Use	dependency	injection

Back	in	the	 	TodoController	,	add	some	code	to	work	with	the

	ITodoItemService	:

public	class	TodoController	:	Controller

{

				private	readonly	ITodoItemService	_todoItemService;

				public	TodoController(ITodoItemService	todoItemService)

				{

								_todoItemService	=	todoItemService;

				}

				public	IActionResult	Index()

				{

								//	Get	to-do	items	from	database

								//	Put	items	into	a	model

								//	Pass	the	view	to	a	model	and	render

				}

}

Since	 	ITodoItemService		is	in	the	 	Services		namespace,	you'll	also	need

to	add	a	 	using		statement	at	the	top:

using	AspNetCoreTodo.Services;

The	first	line	of	the	class	declares	a	private	variable	to	hold	a	reference	to

the	 	ITodoItemService	.	This	variable	lets	you	use	the	service	from	the

	Index		action	method	later	(you'll	see	how	in	a	minute).

The	 	public	TodoController(ITodoItemService	todoItemService)		line

defines	a	constructor	for	the	class.	The	constructor	is	a	special	method

that	is	called	when	you	want	to	create	a	new	instance	of	a	class	(the

36

Use	dependency	injection

	TodoController		class,	in	this	case).	By	adding	an	 	ITodoItemService	

parameter	to	the	constructor,	you've	declared	that	in	order	to	create	the

	TodoController	,	you'll	need	to	provide	an	object	that	matches	the

	ITodoItemService		interface.

Interfaces	are	awesome	because	they	help	decouple	(separate)	the

logic	of	your	application.	Since	the	controller	depends	on	the

	ITodoItemService		interface,	and	not	on	any	specific	class,	it

doesn't	know	or	care	which	class	it's	actually	given.	It	could	be	the

	FakeTodoItemService	,	a	different	one	that	talks	to	a	live	database,

or	something	else!	As	long	as	it	matches	the	interface,	the

controller	can	use	it.	This	makes	it	really	easy	to	test	parts	of	your

application	separately.	I'll	cover	testing	in	detail	in	the	Automated

testing	chapter.

Now	you	can	finally	use	the	 	ITodoItemService		(via	the	private	variable

you	declared)	in	your	action	method	to	get	to-do	items	from	the	service

layer:

public	IActionResult	Index()

{

				var	items	=	await	_todoItemService.GetIncompleteItemsAsync();

				//	...

}

Remember	that	the	 	GetIncompleteItemsAsync		method	returned	a

	Task<TodoItem[]>	?	Returning	a	 	Task		means	that	the	method	won't

necessarily	have	a	result	right	away,	but	you	can	use	the	 	await		keyword

to	make	sure	your	code	waits	until	the	result	is	ready	before	continuing

on.

The	 	Task		pattern	is	common	when	your	code	calls	out	to	a	database	or

an	API	service,	because	it	won't	be	able	to	return	a	real	result	until	the

database	(or	network)	responds.	If	you've	used	promises	or	callbacks	in

37

Use	dependency	injection

JavaScript	or	other	languages,	 	Task		is	the	same	idea:	the	promise	that

there	will	be	a	result	-	sometime	in	the	future.

If	you've	had	to	deal	with	"callback	hell"	in	older	JavaScript	code,

you're	in	luck.	Dealing	with	asynchronous	code	in	.NET	is	much

easier	thanks	to	the	magic	of	the	 	await		keyword!	 	await		lets

your	code	pause	on	an	async	operation,	and	then	pick	up	where	it

left	off	when	the	underlying	database	or	network	request	finishes.

In	the	meantime,	your	application	isn't	blocked,	because	it	can

process	other	requests	as	needed.	This	pattern	is	simple	but	takes

a	little	getting	used	to,	so	don't	worry	if	this	doesn't	make	sense

right	away.	Just	keep	following	along!

The	only	catch	is	that	you	need	to	update	the	 	Index		method	signature

to	return	a	 	Task<IActionResult>		instead	of	just	 	IActionResult	,	and

mark	it	as	 	async	:

public	async	Task<IActionResult>	Index()

{

				var	items	=	await	_todoItemService.GetIncompleteItemsAsync();

				//	Put	items	into	a	model

				//	Pass	the	view	to	a	model	and	render

}

You're	almost	there!	You've	made	the	 	TodoController		depend	on	the

	ITodoItemService		interface,	but	you	haven't	yet	told	ASP.NET	Core	that

you	want	the	 	FakeTodoItemService		to	be	the	actual	service	that's	used

under	the	hood.	It	might	seem	obvious	right	now	since	you	only	have

one	class	that	implements	 	ITodoItemService	,	but	later	you'll	have

multiple	classes	that	implement	the	same	interface,	so	being	explicit	is

necessary.

38

Use	dependency	injection

Declaring	(or	"wiring	up")	which	concrete	class	to	use	for	each	interface

is	done	in	the	 	ConfigureServices		method	of	the	 	Startup		class.	Right

now,	it	looks	something	like	this:

Startup.cs

public	void	ConfigureServices(IServiceCollection	services)

{

				//	(...	some	code)

				services.AddMvc();

}

The	job	of	the	 	ConfigureServices		method	is	adding	things	to	the	service

container,	or	the	collection	of	services	that	ASP.NET	Core	knows	about.

The	 	services.AddMvc		line	adds	the	services	that	the	internal	ASP.NET

Core	systems	need	(as	an	experiment,	try	commenting	out	this	line).	Any

other	services	you	want	to	use	in	your	application	must	be	added	to	the

service	container	here	in	 	ConfigureServices	.

Add	the	following	line	anywhere	inside	the	 	ConfigureServices		method:

services.AddSingleton<ITodoItemService,	FakeTodoItemService>();

This	line	tells	ASP.NET	Core	to	use	the	 	FakeTodoItemService		whenever

the	 	ITodoItemService		interface	is	requested	in	a	constructor	(or

anywhere	else).

	AddSingleton		adds	your	service	to	the	service	container	as	a	singleton.

This	means	that	only	one	copy	of	the	 	FakeTodoItemService		is	created,

and	it's	reused	whenever	the	service	is	requested.	Later,	when	you	write

a	different	service	class	that	talks	to	a	database,	you'll	use	a	different

approach	(called	scoped)	instead.	I'll	explain	why	in	the	Use	a	database

chapter.

39

Use	dependency	injection

That's	it!	When	a	request	comes	in	and	is	routed	to	the	 	TodoController	,

ASP.NET	Core	will	look	at	the	available	services	and	automatically	supply

the	 	FakeTodoItemService		when	the	controller	asks	for	an

	ITodoItemService	.	Because	the	services	are	"injected"	from	the	service

container,	this	pattern	is	called	dependency	injection.

40

Finish	the	controller

Finish	the	controller

The	last	step	is	to	finish	the	controller	code.	The	controller	now	has	a	list

of	to-do	items	from	the	service	layer,	and	it	needs	to	put	those	items	into

a	 	TodoViewModel		and	bind	that	model	to	the	view	you	created	earlier:

Controllers/TodoController.cs

public	async	Task<IActionResult>	Index()

{

				var	items	=	await	_todoItemService.GetIncompleteItemsAsync();

				var	model	=	new	TodoViewModel()

				{

								Items	=	items

				};

				return	View(model);

}

If	you	haven't	already,	make	sure	these	 	using		statements	are	at	the	top

of	the	file:

using	AspNetCoreTodo.Services;

using	AspNetCoreTodo.Models;

If	you're	using	Visual	Studio	or	Visual	Studio	Code,	the	editor	will	suggest

these	 	using		statements	when	you	put	your	cursor	on	a	red	squiggly

line.

Test	it	out

41

Finish	the	controller

To	start	the	application,	press	F5	(if	you're	using	Visual	Studio	or	Visual

Studio	Code),	or	just	type	 	dotnet	run		in	the	terminal.	If	the	code

compiles	without	errors,	the	server	will	start	up	on	port	5000	by	default.

If	your	web	browser	didn't	open	automatically,	open	it	and	navigate	to

http://localhost:5000/todo.	You'll	see	the	view	you	created,	with	the

data	pulled	from	your	fake	database	(for	now).

Although	it's	possible	to	go	directly	to	 	http://localhost:5000/todo	,	it

would	be	nicer	to	add	an	item	called	My	to-dos	to	the	navbar.	To	do	this,

you	can	edit	the	shared	layout	file.

42

Update	the	layout

Update	the	layout

The	layout	file	at	 	Views/Shared/_Layout.cshtml		contains	the	"base"

HTML	for	each	view.	This	includes	the	navbar,	which	is	rendered	at	the

top	of	each	page.

To	add	a	new	item	to	the	navbar,	find	the	HTML	code	for	the	existing

navbar	items:

Views/Shared/_Layout.cshtml

<ul	class="nav	navbar-nav">

				<li><a	asp-area=""	asp-controller="Home"	asp-action="Index">

								Home

				</a></li>

				<li><a	asp-area=""	asp-controller="Home"	asp-action="About">

								About

				</a></li>

				<li><a	asp-area=""	asp-controller="Home"	asp-action="Contact">

								Contact

				</a></li>

</ul>

Add	your	own	item	that	points	to	the	 	Todo		controller	instead	of	 	Home	:

<li>

				<a	asp-controller="Todo"	asp-action="Index">My	to-dos</a>

</li>

The	 	asp-controller		and	 	asp-action		attributes	on	the	 	<a>		element

are	called	tag	helpers.	Before	the	view	is	rendered,	ASP.NET	Core

replaces	these	tag	helpers	with	real	HTML	attributes.	In	this	case,	a	URL

to	the	 	/Todo/Index		route	is	generated	and	added	to	the	 	<a>		element

43

Update	the	layout

as	an	 	href		attribute.	This	means	you	don't	have	to	hard-code	the	route

to	the	 	TodoController	.	Instead,	ASP.NET	Core	generates	it	for	you

automatically.

If	you've	used	Razor	in	ASP.NET	4.x,	you'll	notice	some	syntax

changes.	Instead	of	using	 	@Html.ActionLink()		to	generate	a	link

to	an	action,	tag	helpers	are	now	the	recommended	way	to	create

links	in	your	views.	Tag	helpers	are	useful	for	forms,	too	(you'll	see

why	in	a	later	chapter).	You	can	learn	about	other	tag	helpers	in

the	documentation	at	https://docs.asp.net.

44

Add	external	packages

Add	external	packages

One	of	the	big	advantages	of	using	a	mature	ecosystem	like	.NET	is	that

the	number	of	third-party	packages	and	plugins	is	huge.	Just	like	other

package	systems,	you	can	download	and	install	.NET	packages	that	help

with	almost	any	task	or	problem	you	can	imagine.

NuGet	is	both	the	package	manager	tool	and	the	official	package

repository	(at	https://www.nuget.org).	You	can	search	for	NuGet

packages	on	the	web,	and	install	them	from	your	local	machine	through

the	terminal	(or	the	GUI,	if	you're	using	Visual	Studio).

Install	the	Humanizer	package

At	the	end	of	the	last	chapter,	the	to-do	application	displayed	to-do

items	like	this:

The	due	date	column	is	displaying	dates	in	a	format	that's	good	for

machines	(called	ISO	8601),	but	clunky	for	humans.	Wouldn't	it	be	nicer

if	it	simply	read	"X	days	from	now"?

You	could	write	code	yourself	that	converted	an	ISO	8601	date	into	a

human-friendly	string,	but	fortunately,	there's	a	faster	way.

The	Humanizer	package	on	NuGet	solves	this	problem	by	providing

methods	that	can	"humanize"	or	rewrite	almost	anything:	dates,	times,

durations,	numbers,	and	so	on.	It's	a	fantastic	and	useful	open-source

45

Add	external	packages

project	that's	published	under	the	permissive	MIT	license.

To	add	it	to	your	project,	run	this	command	in	the	terminal:

dotnet	add	package	Humanizer

If	you	peek	at	the	 	AspNetCoreTodo.csproj		project	file,	you'll	see	a	new

	PackageReference		line	that	references	 	Humanizer	.

Use	Humanizer	in	the	view

To	use	a	package	in	your	code,	you	usually	need	to	add	a	 	using	

statement	that	imports	the	package	at	the	top	of	the	file.

Since	Humanizer	will	be	used	to	rewrite	dates	rendered	in	the	view,	you

can	use	it	directly	in	the	view	itself.	First,	add	a	 	@using		statement	at	the

top	of	the	view:

Views/Todo/Index.cshtml

@model	TodoViewModel

@using	Humanizer

//	...

Then,	update	the	line	that	writes	the	 	DueAt		property	to	use	Humanizer's

	Humanize		method:

<td>@item.DueAt.Humanize()</td>

Now	the	dates	are	much	more	readable:

46

Add	external	packages

There	are	packages	available	on	NuGet	for	everything	from	parsing	XML

to	machine	learning	to	posting	to	Twitter.	ASP.NET	Core	itself,	under	the

hood,	is	nothing	more	than	a	collection	of	NuGet	packages	that	are

added	to	your	project.

The	project	file	created	by	 	dotnet	new	mvc		includes	a	single

reference	to	the	 	Microsoft.AspNetCore.All		package,	which	is	a

convenient	"metapackage"	that	references	all	of	the	other

ASP.NET	Core	packages	you	need	for	a	typical	project.	That	way,

you	don't	need	to	have	hundreds	of	package	references	in	your

project	file.

In	the	next	chapter,	you'll	use	another	set	of	NuGet	packages	(a	system

called	Entity	Framework	Core)	to	write	code	that	interacts	with	a

database.

47

Use	a	database

Use	a	database

Writing	database	code	can	be	tricky.	Unless	you	really	know	what	you're

doing,	it's	a	bad	idea	to	paste	raw	SQL	query	strings	into	your	application

code.	An	object-relational	mapper	(ORM)	makes	it	easier	to	write	code

that	interacts	with	a	database	by	adding	a	layer	of	abstraction	between

your	code	and	the	database	itself.	Hibernate	in	Java	and	ActiveRecord	in

Ruby	are	two	well-known	ORMs.

There	are	a	number	of	ORMs	for	.NET,	including	one	built	by	Microsoft

and	included	in	ASP.NET	Core	by	default:	Entity	Framework	Core.	Entity

Framework	Core	makes	it	easy	to	connect	to	a	number	of	different

database	types,	and	lets	you	use	C#	code	to	create	database	queries	that

are	mapped	back	into	C#	models	(POCOs).

Remember	how	creating	a	service	interface	decoupled	the

controller	code	from	the	actual	service	class?	Entity	Framework

Core	is	like	a	big	interface	over	your	database.	Your	C#	code	can

stay	database-agnostic,	and	you	can	swap	out	different	providers

depending	on	the	underlying	database	technology.

Entity	Framework	Core	can	connect	to	relational	databases	like	SQL

Server,	PostgreSQL,	and	MySQL,	and	also	works	with	NoSQL	(document)

databases	like	Mongo.	During	development,	you'll	use	SQLite	in	this

project	to	make	things	easy	to	set	up.

48

Connect	to	a	database

Connect	to	a	database

There	are	a	few	things	you	need	to	use	Entity	Framework	Core	to

connect	to	a	database.	Since	you	used	 	dotnet	new		and	the	MVC	+

Individual	Auth	template	to	set	your	project,	you've	already	got	them:

The	Entity	Framework	Core	packages.	These	are	included	by	default

in	all	ASP.NET	Core	projects.

A	database	(naturally).	The	 	app.db		file	in	the	project	root	directory

is	a	small	SQLite	database	created	for	you	by	 	dotnet	new	.	SQLite	is

a	lightweight	database	engine	that	can	run	without	requiring	you	to

install	any	extra	tools	on	your	machine,	so	it's	easy	and	quick	to	use

in	development.

A	database	context	class.	The	database	context	is	a	C#	class	that

provides	an	entry	point	into	the	database.	It's	how	your	code	will

interact	with	the	database	to	read	and	save	items.	A	basic	context

class	already	exists	in	the	 	Data/ApplicationDbContext.cs		file.

A	connection	string.	Whether	you	are	connecting	to	a	local	file

database	(like	SQLite)	or	a	database	hosted	elsewhere,	you'll	define

a	string	that	contains	the	name	or	address	of	the	database	to

connect	to.	This	is	already	set	up	for	you	in	the	 	appsettings.json	

file:	the	connection	string	for	the	SQLite	database	is

	DataSource=app.db	.

Entity	Framework	Core	uses	the	database	context,	together	with	the

connection	string,	to	establish	a	connection	to	the	database.	You	need	to

tell	Entity	Framework	Core	which	context,	connection	string,	and

database	provider	to	use	in	the	 	ConfigureServices		method	of	the

	Startup		class.	Here's	what's	defined	for	you,	thanks	to	the	template:

services.AddDbContext<ApplicationDbContext>(options	=>

49

Connect	to	a	database

				options.UseSqlite(

								Configuration.GetConnectionString("DefaultConnection")));

This	code	adds	the	 	ApplicationDbContext		to	the	service	container,	and

tells	Entity	Framework	Core	to	use	the	SQLite	database	provider,	with

the	connection	string	from	configuration	( 	appsettings.json	).

As	you	can	see,	 	dotnet	new		creates	a	lot	of	stuff	for	you!	The	database

is	set	up	and	ready	to	be	used.	However,	it	doesn't	have	any	tables	for

storing	to-do	items.	In	order	to	store	your	 	TodoItem		entities,	you'll	need

to	update	the	context	and	migrate	the	database.

50

Update	the	context

Update	the	context

There's	not	a	whole	lot	going	on	in	the	database	context	yet:

Data/ApplicationDbContext.cs

public	class	ApplicationDbContext	

													:	IdentityDbContext<ApplicationUser>

{

				public	ApplicationDbContext(

								DbContextOptions<ApplicationDbContext>	options)

								:	base(options)

				{

				}

				protected	override	void	OnModelCreating(ModelBuilder	builder)

				{

								base.OnModelCreating(builder);

								//	...

				}

}

Add	a	 	DbSet		property	to	the	 	ApplicationDbContext	,	right	below	the

constructor:

public	ApplicationDbContext(

				DbContextOptions<ApplicationDbContext>	options)

				:	base(options)

{

}

public	DbSet<TodoItem>	Items	{	get;	set;	}

//	...

51

Update	the	context

A	 	DbSet		represents	a	table	or	collection	in	the	database.	By	creating	a

	DbSet<TodoItem>		property	called	 	Items	,	you're	telling	Entity

Framework	Core	that	you	want	to	store	 	TodoItem		entities	in	a	table

called	 	Items	.

You've	updated	the	context	class,	but	now	there's	one	small	problem:	the

context	and	database	are	now	out	of	sync,	because	there	isn't	actually	an

	Items		table	in	the	database.	(Just	updating	the	code	of	the	context	class

doesn't	change	the	database	itself.)

In	order	to	update	the	database	to	reflect	the	change	you	just	made	to

the	context,	you	need	to	create	a	migration.

If	you	already	have	an	existing	database,	search	the	web	for

"scaffold-dbcontext	existing	database"	and	read	Microsoft's

documentation	on	using	the	 	Scaffold-DbContext		tool	to	reverse-

engineer	your	database	structure	into	the	proper	 	DbContext		and

model	classes	automatically.

52

Create	a	migration

Create	a	migration

Migrations	keep	track	of	changes	to	the	database	structure	over	time.

They	make	it	possible	to	undo	(roll	back)	a	set	of	changes,	or	create	a

second	database	with	the	same	structure	as	the	first.	With	migrations,

you	have	a	full	history	of	modifications	like	adding	or	removing	columns

(and	entire	tables).

In	the	previous	chapter,	you	added	an	 	Items		set	to	the	context.	Since

the	context	now	includes	a	set	(or	table)	that	doesn't	exist	in	the

database,	you	need	to	create	a	migration	to	update	the	database:

dotnet	ef	migrations	add	AddItems

This	creates	a	new	migration	called	 	AddItems		by	examining	any	changes

you've	made	to	the	context.

If	you	get	an	error	like	 	No	executable	found	matching	command

"dotnet-ef"	,	make	sure	you're	in	the	right	directory.	These

commands	must	be	run	from	the	project	root	directory	(where	the

	Program.cs		file	is).

If	you	open	up	the	 	Data/Migrations		directory,	you'll	see	a	few	files:

53

Create	a	migration

The	first	migration	file	(with	a	name	like	 	00_CreateIdentitySchema.cs	)

was	created	and	applied	for	you	way	back	when	you	ran	 	dotnet	new	.

Your	new	 	AddItem		migration	is	prefixed	with	a	timestamp	when	you

create	it.

You	can	see	a	list	of	migrations	with	 	dotnet	ef	migrations	list	.

If	you	open	your	migration	file,	you'll	see	two	methods	called	 	Up		and

	Down	:

Data/Migrations/_AddItems.cs

protected	override	void	Up(MigrationBuilder	migrationBuilder)

{

				//	(...	some	code)

				migrationBuilder.CreateTable(

								name:	"Items",

								columns:	table	=>	new

								{

												Id	=	table.Column<Guid>(nullable:	false),

												DueAt	=	table.Column<DateTimeOffset>(nullable:	true),

												IsDone	=	table.Column<bool>(nullable:	false),

												Title	=	table.Column<string>(nullable:	true)

								},

								constraints:	table	=>

								{

												table.PrimaryKey("PK_Items",	x	=>	x.Id);

								});

				//	(some	code...)

}

protected	override	void	Down(MigrationBuilder	migrationBuilder)

{

				//	(...	some	code)

				migrationBuilder.DropTable(

								name:	"Items");

				//	(some	code...)

}

54

Create	a	migration

The	 	Up		method	runs	when	you	apply	the	migration	to	the	database.

Since	you	added	a	 	DbSet<TodoItem>		to	the	database	context,	Entity

Framework	Core	will	create	an	 	Items		table	(with	columns	that	match	a

	TodoItem	)	when	you	apply	the	migration.

The	 	Down		method	does	the	opposite:	if	you	need	to	undo	(roll	back)	the

migration,	the	 	Items		table	will	be	dropped.

Workaround	for	SQLite	limitations

There	are	some	limitations	of	SQLite	that	get	in	the	way	if	you	try	to	run

the	migration	as-is.	Until	this	problem	is	fixed,	use	this	workaround:

Comment	out	or	remove	the	 	migrationBuilder.AddForeignKey		lines

in	the	 	Up		method.

Comment	out	or	remove	any	 	migrationBuilder.DropForeignKey		lines

in	the	 	Down		method.

If	you	use	a	full-fledged	SQL	database,	like	SQL	Server	or	MySQL,	this

won't	be	an	issue	and	you	won't	need	to	do	this	(admittedly	hackish)

workaround.

Apply	the	migration

The	final	step	after	creating	one	(or	more)	migrations	is	to	actually	apply

them	to	the	database:

dotnet	ef	database	update

This	command	will	cause	Entity	Framework	Core	to	create	the	 	Items	

table	in	the	database.

55

Create	a	migration

If	you	want	to	roll	back	the	database,	you	can	provide	the	name	of

the	previous	migration:	 	dotnet	ef	database	update

CreateIdentitySchema		This	will	run	the	 	Down		methods	of	any

migrations	newer	than	the	migration	you	specify.

If	you	need	to	completely	erase	the	database	and	start	over,	run

	dotnet	ef	database	drop		followed	by	 	dotnet	ef	database	update	

to	re-scaffold	the	database	and	bring	it	up	to	the	current

migration.

That's	it!	Both	the	database	and	the	context	are	ready	to	go.	Next,	you'll

use	the	context	in	your	service	layer.

56

Create	a	new	service	class

Create	a	new	service	class

Back	in	the	MVC	basics	chapter,	you	created	a	 	FakeTodoItemService		that

contained	hard-coded	to-do	items.	Now	that	you	have	a	database

context,	you	can	create	a	new	service	class	that	will	use	Entity

Framework	Core	to	get	the	real	items	from	the	database.

Delete	the	 	FakeTodoItemService.cs		file,	and	create	a	new	file:

Services/TodoItemService.cs

using	System;

using	System.Collections.Generic;

using	System.Linq;

using	System.Threading.Tasks;

using	AspNetCoreTodo.Data;

using	AspNetCoreTodo.Models;

using	Microsoft.EntityFrameworkCore;

namespace	AspNetCoreTodo.Services

{

				public	class	TodoItemService	:	ITodoItemService

				{

								private	readonly	ApplicationDbContext	_context;

								public	TodoItemService(ApplicationDbContext	context)

								{

												_context	=	context;

								}

								public	async	Task<TodoItem[]>	GetIncompleteItemsAsync()

								{

												return	await	_context.Items

																.Where(x	=>	x.IsDone	==	false)

																.ToArrayAsync();

								}

				}

}

57

Create	a	new	service	class

You'll	notice	the	same	dependency	injection	pattern	here	that	you	saw	in

the	MVC	basics	chapter,	except	this	time	it's	the	 	ApplicationDbContext	

that's	getting	injected.	The	 	ApplicationDbContext		is	already	being	added

to	the	service	container	in	the	 	ConfigureServices		method,	so	it's

available	for	injection	here.

Let's	take	a	closer	look	at	the	code	of	the	 	GetIncompleteItemsAsync	

method.	First,	it	uses	the	 	Items		property	of	the	context	to	access	all	the

to-do	items	in	the	 	DbSet	:

var	items	=	await	_context.Items

Then,	the	 	Where		method	is	used	to	filter	only	the	items	that	are	not

complete:

.Where(x	=>	x.IsDone	==	false)

The	 	Where		method	is	a	feature	of	C#	called	LINQ	(language	integrated

query),	which	takes	inspiration	from	functional	programming	and	makes

it	easy	to	express	database	queries	in	code.	Under	the	hood,	Entity

Framework	Core	translates	the	 	Where		method	into	a	statement	like

	SELECT	*	FROM	Items	WHERE	IsDone	=	0	,	or	an	equivalent	query	document

in	a	NoSQL	database.

Finally,	the	 	ToArrayAsync		method	tells	Entity	Framework	Core	to	get	all

the	entities	that	matched	the	filter	and	return	them	as	an	array.	The

	ToArrayAsync		method	is	asynchronous	(it	returns	a	 	Task	),	so	it	must	be

	await	ed	to	get	its	value.

To	make	the	method	a	little	shorter,	you	can	remove	the	intermediate

	items		variable	and	just	return	the	result	of	the	query	directly	(which

does	the	same	thing):

public	async	Task<TodoItem[]>	GetIncompleteItemsAsync()

58

Create	a	new	service	class

{

				return	await	_context.Items

								.Where(x	=>	x.IsDone	==	false)

								.ToArrayAsync();

}

Update	the	service	container

Because	you	deleted	the	 	FakeTodoItemService		class,	you'll	need	to

update	the	line	in	 	ConfigureServices		that	is	wiring	up	the

	ITodoItemService		interface:

services.AddScoped<ITodoItemService,	TodoItemService>();

	AddScoped		adds	your	service	to	the	service	container	using	the	scoped

lifecycle.	This	means	that	a	new	instance	of	the	 	TodoItemService		class

will	be	created	during	each	web	request.	This	is	required	for	service

classes	that	interact	with	a	database.

Adding	a	service	class	that	interacts	with	Entity	Framework	Core

(and	your	database)	with	the	singleton	lifecycle	(or	other	lifecycles)

can	cause	problems,	because	of	how	Entity	Framework	Core

manages	database	connections	per	request	under	the	hood.	To

avoid	that,	always	use	the	scoped	lifecycle	for	services	that

interact	with	Entity	Framework	Core.

The	 	TodoController		that	depends	on	an	injected	 	ITodoItemService		will

be	blissfully	unaware	of	the	change	in	services	classes,	but	under	the

hood	it'll	be	using	Entity	Framework	Core	and	talking	to	a	real	database!

Test	it	out

Start	up	the	application	and	navigate	to	 	http://localhost:5000/todo	.

The	fake	items	are	gone,	and	your	application	is	making	real	queries	to

the	database.	There	doesn't	happen	to	be	any	saved	to-do	items,	so	it's

59

Create	a	new	service	class

blank	for	now.

In	the	next	chapter,	you'll	add	more	features	to	the	application,	starting

with	the	ability	to	create	new	to-do	items.

60

Add	more	features

Add	more	features

Now	that	you've	connected	to	a	database	using	Entity	Framework	Core,

you're	ready	to	add	some	more	features	to	the	application.	First,	you'll

make	it	possible	to	add	new	to-do	items	using	a	form.

61

Add	new	to-do	items

Add	new	to-do	items

The	user	will	add	new	to-do	items	with	a	simple	form	below	the	list:

Adding	this	feature	requires	a	few	steps:

Adding	a	form	to	the	view

Creating	a	new	action	on	the	controller	to	handle	the	form

Adding	code	to	the	service	layer	to	update	the	database

Add	a	form

The	 	Views/Todo/Index.cshtml		view	has	a	placeholder	for	the	Add	Item

form:

<div	class="panel-footer	add-item-form">

		<!--	TODO:	Add	item	form	-->

</div>

To	keep	things	separate	and	organized,	you'll	create	the	form	as	a	partial

view.	A	partial	view	is	a	small	piece	of	a	larger	view	that	lives	in	a

separate	file.

Create	an	 	AddItemPartial.cshtml		view:

Views/Todo/AddItemPartial.cshtml

62

Add	new	to-do	items

@model	TodoItem

<form	asp-action="AddItem"	method="POST">

				<label	asp-for="Title">Add	a	new	item:</label>

				<input	asp-for="Title">

				<button	type="submit">Add</button>

</form>

The	 	asp-action		tag	helper	can	generate	a	URL	for	the	form,	just	like

when	you	use	it	on	an	 	<a>		element.	In	this	case,	the	 	asp-action		helper

gets	replaced	with	the	real	path	to	the	 	AddItem		route	you'll	create:

<form	action="/Todo/AddItem"	method="POST">

Adding	an	 	asp-		tag	helper	to	the	 	<form>		element	also	adds	a	hidden

field	to	the	form	containing	a	verification	token.	This	verification	token

can	be	used	to	prevent	cross-site	request	forgery	(CSRF)	attacks.	You'll

verify	the	token	when	you	write	the	action.

That	takes	care	of	creating	the	partial	view.	Now,	reference	it	from	the

main	Todo	view:

Views/Todo/Index.cshtml

<div	class="panel-footer	add-item-form">

		@await	Html.PartialAsync("AddItemPartial",	new	TodoItem())

</div>

Add	an	action

When	a	user	clicks	Add	on	the	form	you	just	created,	their	browser	will

construct	a	POST	request	to	 	/Todo/AddItem		on	your	application.	That

won't	work	right	now,	because	there	isn't	any	action	that	can	handle	the

	/Todo/AddItem		route.	If	you	try	it	now,	ASP.NET	Core	will	return	a	 	404

Not	Found		error.

63

Add	new	to-do	items

You'll	need	to	create	a	new	action	called	 	AddItem		on	the

	TodoController	:

[ValidateAntiForgeryToken]

public	async	Task<IActionResult>	AddItem(TodoItem	newItem)

{

				if	(!ModelState.IsValid)

				{

								return	RedirectToAction("Index");

				}

				var	successful	=	await	_todoItemService.AddItemAsync(newItem);

				if	(!successful)

				{

								return	BadRequest("Could	not	add	item.");

				}

				return	RedirectToAction("Index");

}

Notice	how	the	new	 	AddItem		action	accepts	a	 	TodoItem		parameter?

This	is	the	same	 	TodoItem		model	you	created	in	the	MVC	basics	chapter

to	store	information	about	a	to-do	item.	When	it's	used	here	as	an	action

parameter,	ASP.NET	Core	will	automatically	perform	a	process	called

model	binding.

Model	binding	looks	at	the	data	in	a	request	and	tries	to	intelligently

match	the	incoming	fields	with	properties	on	the	model.	In	other	words,

when	the	user	submits	this	form	and	their	browser	POSTs	to	this	action,

ASP.NET	Core	will	grab	the	information	from	the	form	and	place	it	in	the

	newItem		variable.

The	 	[ValidateAntiForgeryToken]		attribute	before	the	action	tells

ASP.NET	Core	that	it	should	look	for	(and	verify)	the	hidden	verification

token	that	was	added	to	the	form	by	the	 	asp-action		tag	helper.	This	is

an	important	security	measure	to	prevent	cross-site	request	forgery

64

Add	new	to-do	items

(CSRF)	attacks,	where	your	users	could	be	tricked	into	submitting	data

from	a	malicious	site.	The	verification	token	ensures	that	your	application

is	actually	the	one	that	rendered	and	submitted	the	form.

Take	a	look	at	the	 	AddItemPartial.cshtml		view	once	more.	The	 	@model

TodoItem		line	at	the	top	of	the	file	tells	ASP.NET	Core	that	the	view

should	expect	to	be	paired	with	the	 	TodoItem		model.	This	makes	it

possible	to	use	 	asp-for="Title"		on	the	 	<input>		tag	to	let	ASP.NET

Core	know	that	this	input	element	is	for	the	 	Title		property.

Because	of	the	 	@model		line,	the	partial	view	will	expect	to	be	passed	a

	TodoItem		object	when	it's	rendered.	Passing	it	a	 	new	TodoItem		via

	Html.PartialAsync		initializes	the	form	with	an	empty	item.	(Try

appending	 	{	Title	=	"hello"	}		and	see	what	happens!)

During	model	binding,	any	model	properties	that	can't	be	matched	up

with	fields	in	the	request	are	ignored.	Since	the	form	only	includes	a

	Title		input	element,	you	can	expect	that	the	other	properties	on

	TodoItem		(the	 	IsDone		flag,	the	 	DueAt		date)	will	be	empty	or	contain

default	values.

Instead	of	reusing	the	 	TodoItem		model,	another	approach	would

be	to	create	a	separate	model	(like	 	NewTodoItem	)	that's	only	used

for	this	action	and	only	has	the	specific	properties	(Title)	you	need

for	adding	a	new	to-do	item.	Model	binding	is	still	used,	but	this

way	you've	separated	the	model	that's	used	for	storing	a	to-do

item	in	the	database	from	the	model	that's	used	for	binding

incoming	request	data.	This	is	sometimes	called	a	binding	model	or

a	data	transfer	object	(DTO).	This	pattern	is	common	in	larger,

more	complex	projects.

After	binding	the	request	data	to	the	model,	ASP.NET	Core	also

performs	model	validation.	Validation	checks	whether	the	data	bound	to

the	model	from	the	incoming	request	makes	sense	or	is	valid.	You	can

65

Add	new	to-do	items

add	attributes	to	the	model	to	tell	ASP.NET	Core	how	it	should	be

validated.

The	 	[Required]		attribute	on	the	 	Title		property	tells	ASP.NET	Core's

model	validator	to	consider	the	title	invalid	if	it	is	missing	or	blank.	Take	a

look	at	the	code	of	the	 	AddItem		action:	the	first	block	checks	whether

the	 	ModelState		(the	model	validation	result)	is	valid.	It's	customary	to	do

this	validation	check	right	at	the	beginning	of	the	action:

if	(!ModelState.IsValid)

{

				return	RedirectToAction("Index");

}

If	the	 	ModelState		is	invalid	for	any	reason,	the	browser	will	be

redirected	to	the	 	/Todo/Index		route,	which	refreshes	the	page.

Next,	the	controller	calls	into	the	service	layer	to	do	the	actual	database

operation	of	saving	the	new	to-do	item:

var	successful	=	await	_todoItemService.AddItemAsync(newItem);

if	(!successful)

{

				return	BadRequest(new	{	error	=	"Could	not	add	item."	});

}

The	 	AddItemAsync		method	will	return	 	true		or	 	false		depending	on

whether	the	item	was	successfully	added	to	the	database.	If	it	fails	for

some	reason,	the	action	will	return	an	HTTP	 	400	Bad	Request		error

along	with	an	object	that	contains	an	error	message.

Finally,	if	everything	completed	without	errors,	the	action	redirects	the

browser	to	the	 	/Todo/Index		route,	which	refreshes	the	page	and

displays	the	new,	updated	list	of	to-do	items	to	the	user.

Add	a	service	method

66

Add	new	to-do	items

If	you're	using	a	code	editor	that	understands	C#,	you'll	see	red	squiggely

lines	under	 	AddItemAsync		because	the	method	doesn't	exist	yet.

As	a	last	step,	you	need	to	add	a	method	to	the	service	layer.	First,	add	it

to	the	interface	definition	in	 	ITodoItemService	:

public	interface	ITodoItemService

{

				Task<TodoItem[]>	GetIncompleteItemsAsync();

				Task<bool>	AddItemAsync(TodoItem	newItem);

}

Then,	the	actual	implementation	in	 	TodoItemService	:

public	async	Task<bool>	AddItemAsync(TodoItem	newItem)

{

				newItem.Id	=	Guid.NewGuid();

				newItem.IsDone	=	false;

				newItem.DueAt	=	DateTimeOffset.Now.AddDays(3);

				_context.Items.Add(newItem);

				var	saveResult	=	await	_context.SaveChangesAsync();

				return	saveResult	==	1;

}

The	 	newItem.Title		property	has	already	been	set	by	ASP.NET	Core's

model	binder,	so	this	method	only	needs	to	assign	an	ID	and	set	the

default	values	for	the	other	properties.	Then,	the	new	item	is	added	to

the	database	context.	It	isn't	actually	saved	until	you	call

	SaveChangesAsync()	.	If	the	save	operation	was	successful,

	SaveChangesAsync()		will	return	1.

Try	it	out

67

Add	new	to-do	items

Run	the	application	and	add	some	items	to	your	to-do	list	with	the	form.

Since	the	items	are	being	stored	in	the	database,	they'll	still	be	there

even	after	you	stop	and	start	the	application	again.

As	an	extra	challenge,	try	adding	a	date	picker	using	HTML	and

JavaScript,	and	let	the	user	choose	an	(optional)	date	for	the

	DueAt		property.	Then,	use	that	date	instead	of	always	making

new	tasks	that	are	due	in	3	days.

68

Complete	items	with	a	checkbox

Complete	items	with	a	checkbox

Adding	items	to	your	to-do	list	is	great,	but	eventually	you'll	need	to	get

things	done,	too.	In	the	 	Views/Todo/Index.cshtml		view,	a	checkbox	is

rendered	for	each	to-do	item:

<input	type="checkbox"	class="done-checkbox">

Clicking	the	checkbox	doesn't	do	anything	(yet).	Just	like	the	last	chapter,

you'll	add	this	behavior	using	forms	and	actions.	In	this	case,	you'll	also

need	a	tiny	bit	of	JavaScript	code.

Add	form	elements	to	the	view

First,	update	the	view	and	wrap	each	checkbox	with	a	 	<form>		element.

Then,	add	a	hidden	element	containing	the	item's	ID:

Views/Todo/Index.cshtml

<td>

				<form	asp-action="MarkDone"	method="POST">

								<input	type="checkbox"	class="done-checkbox">

								<input	type="hidden"	name="id"	value="@item.Id">

				</form>

</td>

When	the	 	foreach		loop	runs	in	the	view	and	prints	a	row	for	each	to-do

item,	a	copy	of	this	form	will	exist	in	each	row.	The	hidden	input

containing	the	to-do	item's	ID	makes	it	possible	for	your	controller	code

to	tell	which	box	was	checked.	(Without	it,	you'd	be	able	to	tell	that	some

box	was	checked,	but	not	which	one.)

69

Complete	items	with	a	checkbox

If	you	run	your	application	right	now,	the	checkboxes	still	won't	do

anything,	because	there's	no	submit	button	to	tell	the	browser	to	create

a	POST	request	with	the	form's	data.	You	could	add	a	submit	button

under	each	checkbox,	but	that	would	be	a	silly	user	experience.	Ideally,

clicking	the	checkbox	should	automatically	submit	the	form.	You	can

achieve	that	by	adding	some	JavaScript.

Add	JavaScript	code

Find	the	 	site.js		file	in	the	 	wwwroot/js		directory	and	add	this	code:

wwwroot/js/site.js

$(document).ready(function()	{

				//	Wire	up	all	of	the	checkboxes	to	run	markCompleted()

				$('.done-checkbox').on('click',	function(e)	{

								markCompleted(e.target);

				});

});

function	markCompleted(checkbox)	{

				checkbox.disabled	=	true;

				var	row	=	checkbox.closest('tr');

				$(row).addClass('done');

				var	form	=	checkbox.closest('form');

				form.submit();

}

This	code	first	uses	jQuery	(a	JavaScript	helper	library)	to	attach	some

code	to	the	 	click		even	of	all	the	checkboxes	on	the	page	with	the	CSS

class	 	done-checkbox	.	When	a	checkbox	is	clicked,	the	 	markCompleted()	

function	is	run.

The	 	markCompleted()		function	does	a	few	things:

70

Complete	items	with	a	checkbox

Adds	the	 	disabled		attribute	to	the	checkbox	so	it	can't	be	clicked

again

Adds	the	 	done		CSS	class	to	the	parent	row	that	contains	the

checkbox,	which	changes	the	way	the	row	looks	based	on	the	CSS

rules	in	 	style.css	

Submits	the	form

That	takes	care	of	the	view	and	frontend	code.	Now	it's	time	to	add	a

new	action!

Add	an	action	to	the	controller

As	you've	probably	guessed,	you	need	to	add	an	action	called	 	MarkDone	

in	the	 	TodoController	:

[ValidateAntiForgeryToken]

public	async	Task<IActionResult>	MarkDone(Guid	id)

{

				if	(id	==	Guid.Empty)

				{

								return	RedirectToAction("Index");

				}

				var	successful	=	await	_todoItemService.MarkDoneAsync(id);

				if	(!successful)

				{

								return	BadRequest("Could	not	mark	item	as	done.");

				}

				return	RedirectToAction("Index");

}

Let's	step	through	each	line	of	this	action	method.	First,	the	method

accepts	a	 	Guid		parameter	called	 	id		in	the	method	signature.	Unlike

the	 	AddItem		action,	which	used	a	model	and	model	binding/validation,

the	 	id		parameter	is	very	simple.	If	the	incoming	request	data	includes	a

71

Complete	items	with	a	checkbox

field	called	 	id	,	ASP.NET	Core	will	try	to	parse	it	as	a	guid.	This	works

because	the	hidden	element	you	added	to	the	checkbox	form	is	named

	id	.

Since	you	aren't	using	model	binding,	there's	no	 	ModelState		to	check	for

validity.	Instead,	you	can	check	the	guid	value	directly	to	make	sure	it's

valid.	If	for	some	reason	the	 	id		parameter	in	the	request	was	missing	or

couldn't	be	parsed	as	a	guid,	 	id		will	have	a	value	of	 	Guid.Empty	.	If

that's	the	case,	the	action	tells	the	browser	to	redirect	to	 	/Todo/Index	

and	refresh	the	page.

Next,	the	controller	needs	to	call	the	service	layer	to	update	the

database.	This	will	be	handled	by	a	new	method	called	 	MarkDoneAsync	

on	the	 	ITodoItemService		interface,	which	will	return	true	or	false

depending	on	whether	the	update	succeeded:

var	successful	=	await	_todoItemService.MarkDoneAsync(id);

if	(!successful)

{

				return	BadRequest("Could	not	mark	item	as	done.");

}

Finally,	if	everything	looks	good,	the	browser	is	redirected	to	the

	/Todo/Index		action	and	the	page	is	refreshed.

With	the	view	and	controller	updated,	all	that's	left	is	adding	the	missing

service	method.

Add	a	service	method

First,	add	 	MarkDoneAsync		to	the	interface	definition:

Services/ITodoItemService.cs

Task<bool>	MarkDoneAsync(Guid	id);

72

Complete	items	with	a	checkbox

Then,	add	the	concrete	implementation	to	the	 	TodoItemService	:

Services/TodoItemService.cs

public	async	Task<bool>	MarkDoneAsync(Guid	id)

{

				var	item	=	await	_context.Items

								.Where(x	=>	x.Id	==	id)

								.SingleOrDefaultAsync();

				if	(item	==	null)	return	false;

				item.IsDone	=	true;

				var	saveResult	=	await	_context.SaveChangesAsync();

				return	saveResult	==	1;	//	One	entity	should	have	been	updated

}

This	method	uses	Entity	Framework	Core	and	 	Where()		to	find	an	item

by	ID	in	the	database.	The	 	SingleOrDefaultAsync()		method	will	either

return	the	item	or	 	null		if	it	couldn't	be	found.

Once	you're	sure	that	 	item		isn't	null,	it's	a	simple	matter	of	setting	the

	IsDone		property:

item.IsDone	=	true;

Changing	the	property	only	affects	the	local	copy	of	the	item	until

	SaveChangesAsync()		is	called	to	persist	the	change	back	to	the	database.

	SaveChangesAsync()		returns	a	number	that	indicates	how	many	entities

were	updated	during	the	save	operation.	In	this	case,	it'll	either	be	1	(the

item	was	updated)	or	0	(something	went	wrong).

Try	it	out

73

Complete	items	with	a	checkbox

Run	the	application	and	try	checking	some	items	off	the	list.	Refresh	the

page	and	they'll	disappear	completely,	because	of	the	 	Where()		filter	in

the	 	GetIncompleteItemsAsync()		method.

Right	now,	the	application	contains	a	single,	shared	to-do	list.	It'd	be

even	more	useful	if	it	kept	track	of	individual	to-do	lists	for	each	user.	In

the	next	chapter,	you'll	add	login	and	security	features	to	the	project.

74

Security	and	identity

Security	and	identity

Security	is	a	major	concern	of	any	modern	web	application	or	API.	It's

important	to	keep	your	user	or	customer	data	safe	and	out	of	the	hands

of	attackers.	This	is	a	very	broad	topic,	involving	things	like:

Sanitizing	data	input	to	prevent	SQL	injection	attacks

Preventing	cross-domain	(CSRF)	attacks	in	forms

Using	HTTPS	(connection	encryption)	so	data	can't	be	intercepted	as

it	travels	over	the	Internet

Giving	users	a	way	to	securely	sign	in	with	a	password	or	other

credentials

Designing	password	reset,	account	recovery,	and	multi-factor

authentication	flows

ASP.NET	Core	can	help	make	all	of	this	easier	to	implement.	The	first

two	(protection	against	SQL	injection	and	cross-domain	attacks)	are

already	built-in,	and	you	can	add	a	few	lines	of	code	to	enable	HTTPS

support.	This	chapter	will	mainly	focus	on	the	identity	aspects	of

security:	handling	user	accounts,	authenticating	(logging	in)	your	users

securely,	and	making	authorization	decisions	once	they	are

authenticated.

Authentication	and	authorization	are	distinct	ideas	that	are	often

confused.	Authentication	deals	with	whether	a	user	is	logged	in,

while	authorization	deals	with	what	they	are	allowed	to	do	after

they	log	in.	You	can	think	of	authentication	as	asking	the	question,

"Do	I	know	who	this	user	is?"	While	authorization	asks,	"Does	this

user	have	permission	to	do	X?"

75

Security	and	identity

The	MVC	+	Individual	Authentication	template	you	used	to	scaffold	the

project	includes	a	number	of	classes	built	on	top	of	ASP.NET	Core

Identity,	an	authentication	and	identity	system	that's	part	of	ASP.NET

Core.	Out	of	the	box,	this	adds	the	ability	to	log	in	with	an	email	and

password.

What	is	ASP.NET	Core	Identity?

ASP.NET	Core	Identity	is	the	identity	system	that	ships	with	ASP.NET

Core.	Like	everything	else	in	the	ASP.NET	Core	ecosystem,	it's	a	set	of

NuGet	packages	that	can	be	installed	in	any	project	(and	are	already

included	if	you	use	the	default	template).

ASP.NET	Core	Identity	takes	care	of	storing	user	accounts,	hashing	and

storing	passwords,	and	managing	roles	for	users.	It	supports

email/password	login,	multi-factor	authentication,	social	login	with

providers	like	Google	and	Facebook,	as	well	as	connecting	to	other

services	using	protocols	like	OAuth	2.0	and	OpenID	Connect.

The	Register	and	Login	views	that	ship	with	the	MVC	+	Individual

Authentication	template	already	take	advantage	of	ASP.NET	Core

Identity,	and	they	already	work!	Try	registering	for	an	account	and

logging	in.

76

Require	authentication

Require	authentication

Often	you'll	want	to	require	the	user	to	log	in	before	they	can	access

certain	parts	of	your	application.	For	example,	it	makes	sense	to	show

the	home	page	to	everyone	(whether	you're	logged	in	or	not),	but	only

show	your	to-do	list	after	you've	logged	in.

You	can	use	the	 	[Authorize]		attribute	in	ASP.NET	Core	to	require	a

logged-in	user	for	a	particular	action,	or	an	entire	controller.	To	require

authentication	for	all	actions	of	the	 	TodoController	,	add	the	attribute

above	the	first	line	of	the	controller:

Controllers/TodoController.cs

[Authorize]

public	class	TodoController	:	Controller

{

				//	...

}

Add	this	 	using		statement	at	the	top	of	the	file:

using	Microsoft.AspNetCore.Authorization;

Try	running	the	application	and	accessing	 	/todo		without	being	logged

in.	You'll	be	redirected	to	the	login	page	automatically.

The	 	[Authorize]		attribute	is	actually	doing	an	authentication

check	here,	not	an	authorization	check	(despite	the	name	of	the

attribute).	Later,	you'll	use	the	attribute	to	check	both

authentication	and	authorization.

77

Require	authentication

78

Using	identity	in	the	application

Using	identity	in	the	application

The	to-do	list	items	themselves	are	still	shared	between	all	users,

because	the	stored	to-do	entities	aren't	tied	to	a	particular	user.	Now

that	the	 	[Authorize]		attribute	ensures	that	you	must	be	logged	in	to

see	the	to-do	view,	you	can	filter	the	database	query	based	on	who	is

logged	in.

First,	inject	a	 	UserManager<ApplicationUser>		into	the	 	TodoController	:

Controllers/TodoController.cs

[Authorize]

public	class	TodoController	:	Controller

{

				private	readonly	ITodoItemService	_todoItemService;

				private	readonly	UserManager<ApplicationUser>	_userManager;

				public	TodoController(ITodoItemService	todoItemService,

								UserManager<ApplicationUser>	userManager)

				{

								_todoItemService	=	todoItemService;

								_userManager	=	userManager;

				}

				//	...

}

You'll	need	to	add	a	new	 	using		statement	at	the	top:

using	Microsoft.AspNetCore.Identity;

The	 	UserManager		class	is	part	of	ASP.NET	Core	Identity.	You	can	use	it

to	get	the	current	user	in	the	 	Index		action:

public	async	Task<IActionResult>	Index()

79

Using	identity	in	the	application

{

				var	currentUser	=	await	_userManager.GetUserAsync(User);

				if	(currentUser	==	null)	return	Challenge();

				var	items	=	await	_todoItemService

								.GetIncompleteItemsAsync(currentUser);

				var	model	=	new	TodoViewModel()

				{

								Items	=	items

				};

				return	View(model);

}

The	new	code	at	the	top	of	the	action	method	uses	the	 	UserManager		to

look	up	the	current	user	from	the	 	User		property	available	in	the	action:

var	currentUser	=	await	_userManager.GetUserAsync(User);

If	there	is	a	logged-in	user,	the	 	User		property	contains	a	lightweight

object	with	some	(but	not	all)	of	the	user's	information.	The	 	UserManager	

uses	this	to	look	up	the	full	user	details	in	the	database	via	the

	GetUserAsync()		method.

The	value	of	 	currentUser		should	never	be	null,	because	the

	[Authorize]		attribute	is	present	on	the	controller.	However,	it's	a	good

idea	to	do	a	sanity	check,	just	in	case.	You	can	use	the	 	Challenge()	

method	to	force	the	user	to	log	in	again	if	their	information	is	missing:

if	(currentUser	==	null)	return	Challenge();

Since	you're	now	passing	an	 	ApplicationUser		parameter	to

	GetIncompleteItemsAsync()	,	you'll	need	to	update	the	 	ITodoItemService	

interface:

Services/ITodoItemService.cs

80

Using	identity	in	the	application

public	interface	ITodoItemService

{

				Task<TodoItem[]>	GetIncompleteItemsAsync(

								ApplicationUser	user);

				//	...

}

Since	you	changed	the	 	ITodoItemService		interface,	you	also	need	to

update	the	signature	of	the	 	GetIncompleteItemsAsync()		method	in	the

	TodoItemService	:

Services/TodoItemService

public	async	Task<TodoItem[]>	GetIncompleteItemsAsync(

				ApplicationUser	user)

The	next	step	is	to	update	the	database	query	and	add	a	filter	to	show

only	the	items	created	by	the	current	user.	Before	you	can	do	that,	you

need	to	add	a	new	property	to	the	database.

Update	the	database

You'll	need	to	add	a	new	property	to	the	 	TodoItem		entity	model	so	each

item	can	"remember"	the	user	that	owns	it:

Models/TodoItem.cs

public	string	UserId	{	get;	set;	}

Since	you	updated	the	entity	model	used	by	the	database	context,	you

also	need	to	migrate	the	database.	Create	a	new	migration	using	 	dotnet

ef		in	the	terminal:

dotnet	ef	migrations	add	AddItemUserId

81

Using	identity	in	the	application

This	creates	a	new	migration	called	 	AddItemUserId		which	will	add	a	new

column	to	the	 	Items		table,	mirroring	the	change	you	made	to	the

	TodoItem		model.

Use	 	dotnet	ef		again	to	apply	it	to	the	database:

dotnet	ef	database	update

Update	the	service	class

With	the	database	and	the	database	context	updated,	you	can	now

update	the	 	GetIncompleteItemsAsync()		method	in	the	 	TodoItemService	

and	add	another	clause	to	the	 	Where		statement:

Services/TodoItemService.cs

public	async	Task<TodoItem[]>	GetIncompleteItemsAsync(

				ApplicationUser	user)

{

				return	await	_context.Items

								.Where(x	=>	x.IsDone	==	false	&&	x.UserId	==	user.Id)

								.ToArrayAsync();

}

If	you	run	the	application	and	register	or	log	in,	you'll	see	an	empty	to-do

list	once	again.	Unfortunately,	any	items	you	try	to	add	disappear	into

the	ether,	because	you	haven't	updated	the	 	AddItem		action	to	be	user-

aware	yet.

Update	the	AddItem	and	MarkDone	actions

You'll	need	to	use	the	 	UserManager		to	get	the	current	user	in	the

	AddItem		and	 	MarkDone		action	methods,	just	like	you	did	in	 	Index	.

Here	are	both	updated	methods:

82

Using	identity	in	the	application

Controllers/TodoController.cs

[ValidateAntiForgeryToken]

public	async	Task<IActionResult>	AddItem(TodoItem	newItem)

{

				if	(!ModelState.IsValid)

				{

								return	RedirectToAction("Index");

				}

				var	currentUser	=	await	_userManager.GetUserAsync(User);

				if	(currentUser	==	null)	return	Challenge();

				var	successful	=	await	_todoItemService

								.AddItemAsync(newItem,	currentUser);

				if	(!successful)

				{

								return	BadRequest("Could	not	add	item.");

				}

				return	RedirectToAction("Index");

}

[ValidateAntiForgeryToken]

public	async	Task<IActionResult>	MarkDone(Guid	id)

{

				if	(id	==	Guid.Empty)

				{

								return	RedirectToAction("Index");

				}

				var	currentUser	=	await	_userManager.GetUserAsync(User);

				if	(currentUser	==	null)	return	Challenge();

				var	successful	=	await	_todoItemService

								.MarkDoneAsync(id,	currentUser);

				if	(!successful)

				{

								return	BadRequest("Could	not	mark	item	as	done.");

				}

				return	RedirectToAction("Index");

83

Using	identity	in	the	application

}

Both	service	methods	must	now	accept	an	 	ApplicationUser		parameter.

Update	the	interface	definition	in	 	ITodoItemService	:

Task<bool>	AddItemAsync(TodoItem	newItem,	ApplicationUser	user);

Task<bool>	MarkDoneAsync(Guid	id,	ApplicationUser	user);

And	finally,	update	the	service	method	implementations	in	the

	TodoItemService	.	In	 	AddItemAsync		method,	set	the	 	UserId		property

when	you	construct	a	 	new	TodoItem	:

public	async	Task<bool>	AddItemAsync(

				TodoItem	newItem,	ApplicationUser	user)

{

				newItem.Id	=	Guid.NewGuid();

				newItem.IsDone	=	false;

				newItem.DueAt	=	DateTimeOffset.Now.AddDays(3);

				newItem.UserId	=	user.Id;

				//	...

}

The	 	Where		clause	in	the	 	MarkDoneAsync		method	also	needs	to	check	for

the	user's	ID,	so	a	rogue	user	can't	complete	someone	else's	items	by

guessing	their	IDs:

public	async	Task<bool>	MarkDoneAsync(

				Guid	id,	ApplicationUser	user)

{

				var	item	=	await	_context.Items

								.Where(x	=>	x.Id	==	id	&&	x.UserId	==	user.Id)

								.SingleOrDefaultAsync();

				//	...

}

84

Using	identity	in	the	application

All	done!	Try	using	the	application	with	two	different	user	accounts.	The

to-do	items	stay	private	for	each	account.

85

Authorization	with	roles

Authorization	with	roles

Roles	are	a	common	approach	to	handling	authorization	and	permissions

in	a	web	application.	For	example,	it's	common	to	create	an

Administrator	role	that	gives	admin	users	more	permissions	or	power

than	normal	users.

In	this	project,	you'll	add	a	Manage	Users	page	that	only	administrators

can	see.	If	normal	users	try	to	access	it,	they'll	see	an	error.

Add	a	Manage	Users	page

First,	create	a	new	controller:

Controllers/ManageUsersController.cs

using	System;

using	System.Linq;

using	System.Threading.Tasks;

using	Microsoft.AspNetCore.Mvc;

using	Microsoft.AspNetCore.Authorization;

using	Microsoft.AspNetCore.Identity;

using	AspNetCoreTodo.Models;

using	Microsoft.EntityFrameworkCore;

namespace	AspNetCoreTodo.Controllers

{

				[Authorize(Roles	=	"Administrator")]

				public	class	ManageUsersController	:	Controller

				{

								private	readonly	UserManager<ApplicationUser>

												_userManager;

								public	ManageUsersController(

												UserManager<ApplicationUser>	userManager)

								{

												_userManager	=	userManager;

								}

86

Authorization	with	roles

								public	async	Task<IActionResult>	Index()

								{

												var	admins	=	(await	_userManager

																.GetUsersInRoleAsync("Administrator"))

																.ToArray();

												var	everyone	=	await	_userManager.Users

																.ToArrayAsync();

												var	model	=	new	ManageUsersViewModel

												{

																Administrators	=	admins,

																Everyone	=	everyone

												};

												return	View(model);

								}

				}

}

Setting	the	 	Roles		property	on	the	 	[Authorize]		attribute	will	ensure

that	the	user	must	be	logged	in	and	assigned	the	Administrator	role	in

order	to	view	the	page.

Next,	create	a	view	model:

Models/ManageUsersViewModel.cs

using	System.Collections.Generic;

using	AspNetCoreTodo.Models;

namespace	AspNetCoreTodo.Models

{

				public	class	ManageUsersViewModel

				{

								public	ApplicationUser[]	Administrators	{	get;	set;	}

								public	ApplicationUser[]	Everyone	{	get;	set;}

				}

}

87

Authorization	with	roles

Finally,	create	a	 	Views/ManageUsers		folder	and	a	view	for	the	 	Index	

action:

Views/ManageUsers/Index.cshtml

@model	ManageUsersViewModel

@{

				ViewData["Title"]	=	"Manage	users";

}

<h2>@ViewData["Title"]</h2>

<h3>Administrators</h3>

<table	class="table">

				<thead>

								<tr>

												<td>Id</td>

												<td>Email</td>

								</tr>

				</thead>

				@foreach	(var	user	in	Model.Administrators)

				{

								<tr>

												<td>@user.Id</td>

												<td>@user.Email</td>

								</tr>

				}

</table>

<h3>Everyone</h3>

<table	class="table">

				<thead>

								<tr>

												<td>Id</td>

												<td>Email</td>

								</tr>

				</thead>

				@foreach	(var	user	in	Model.Everyone)

88

Authorization	with	roles

				{

								<tr>

												<td>@user.Id</td>

												<td>@user.Email</td>

								</tr>

				}

</table>

Start	up	the	application	and	try	to	access	the	 	/ManageUsers		route	while

logged	in	as	a	normal	user.	You'll	see	this	access	denied	page:

That's	because	users	aren't	assigned	the	Administrator	role

automatically.

Create	a	test	administrator	account

For	obvious	security	reasons,	it	isn't	possible	for	anyone	to	register	a

new	administrator	account	themselves.	In	fact,	the	Administrator	role

doesn't	even	exist	in	the	database	yet!

You	can	add	the	Administrator	role	plus	a	test	administrator	account	to

the	database	the	first	time	the	application	starts	up.	Adding	first-time

data	to	the	database	is	called	initializing	or	seeding	the	database.

Create	a	new	class	in	the	root	of	the	project	called	 	SeedData	:

89

Authorization	with	roles

SeedData.cs

using	System;

using	System.Threading.Tasks;

using	AspNetCoreTodo.Models;

using	Microsoft.AspNetCore.Identity;

using	Microsoft.EntityFrameworkCore;

using	Microsoft.Extensions.DependencyInjection;

namespace	AspNetCoreTodo

{

				public	static	class	SeedData

				{

								public	static	async	Task	InitializeAsync(

												IServiceProvider	services)

								{

												var	roleManager	=	services

																.GetRequiredService<RoleManager<IdentityRole>>();

												await	EnsureRolesAsync(roleManager);

												var	userManager	=	services

																.GetRequiredService<UserManager<ApplicationUser>>(

);

												await	EnsureTestAdminAsync(userManager);

								}

				}

}

The	 	InitializeAsync()		method	uses	an	 	IServiceProvider		(the

collection	of	services	that	is	set	up	in	the	 	Startup.ConfigureServices()	

method)	to	get	the	 	RoleManager		and	 	UserManager		from	ASP.NET	Core

Identity.

Add	two	more	methods	below	the	 	InitializeAsync()		method.	First,	the

	EnsureRolesAsync()		method:

private	static	async	Task	EnsureRolesAsync(

				RoleManager<IdentityRole>	roleManager)

{

				var	alreadyExists	=	await	roleManager

								.RoleExistsAsync(Constants.AdministratorRole);

90

Authorization	with	roles

				if	(alreadyExists)	return;

				await	roleManager.CreateAsync(

								new	IdentityRole(Constants.AdministratorRole));

}

This	method	checks	to	see	if	an	 	Administrator		role	exists	in	the

database.	If	not,	it	creates	one.	Instead	of	repeatedly	typing	the	string

	"Administrator"	,	create	a	small	class	called	 	Constants		to	hold	the

value:

Constants.cs

namespace	AspNetCoreTodo

{

				public	static	class	Constants

				{

								public	const	string	AdministratorRole	=	"Administrator";

				}

}

If	you	want,	you	can	update	the	 	ManageUsersController		to	use

this	constant	value	as	well.

Next,	write	the	 	EnsureTestAdminAsync()		method:

SeedData.cs

private	static	async	Task	EnsureTestAdminAsync(

				UserManager<ApplicationUser>	userManager)

{

				var	testAdmin	=	await	userManager.Users

								.Where(x	=>	x.UserName	==	"[email protected]")

								.SingleOrDefaultAsync();

				if	(testAdmin	!=	null)	return;

				testAdmin	=	new	ApplicationUser

				{

91

Authorization	with	roles

								UserName	=	"[email protected]",

								Email	=	"[email protected]"

				};

				await	userManager.CreateAsync(

								testAdmin,	"NotSecure123!!");

				await	userManager.AddToRoleAsync(

								testAdmin,	Constants.AdministratorRole);

}

If	there	isn't	already	a	user	with	the	username	 	[email protected]		in	the

database,	this	method	will	create	one	and	assign	a	temporary	password.

After	you	log	in	for	the	first	time,	you	should	change	the	account's

password	to	something	secure!

Next,	you	need	to	tell	your	application	to	run	this	logic	when	it	starts	up.

Modify	 	Program.cs		and	update	 	Main()		to	call	a	new	method,

	InitializeDatabase()	:

Program.cs

public	static	void	Main(string[]	args)

{

				var	host	=	BuildWebHost(args);

				InitializeDatabase(host);

				host.Run();

}

Then,	add	the	new	method	to	the	class	below	 	Main()	:

private	static	void	InitializeDatabase(IWebHost	host)

{

				using	(var	scope	=	host.Services.CreateScope())

				{

								var	services	=	scope.ServiceProvider;

								try

								{

												SeedData.InitializeAsync(services).Wait();

								}

92

Authorization	with	roles

								catch	(Exception	ex)

								{

												var	logger	=	services

																.GetRequiredService<ILogger<Program>>();

												logger.LogError(ex,	"Error	occurred	seeding	the	DB.");

								}

				}

}

Add	this	 	using		statement	to	the	top	of	the	file:

using	Microsoft.Extensions.DependencyInjection;

This	method	gets	the	service	collection	that	 	SeedData.InitializeAsync()	

needs	and	then	runs	the	method	to	seed	the	database.	If	something	goes

wrong,	an	error	is	logged.

Because	 	InitializeAsync()		returns	a	 	Task	,	the	 	Wait()		method

must	be	used	to	make	sure	it	finishes	before	the	application	starts

up.	You'd	normally	use	 	await		for	this,	but	for	technical	reasons

you	can't	use	 	await		in	the	 	Program		class.	This	is	a	rare

exception.	You	should	use	 	await		everywhere	else!

When	you	start	the	application	next,	the	 	[email protected]		account	will

be	created	and	assigned	the	Administrator	role.	Try	logging	in	with	this

account,	and	navigating	to	 	http://localhost:5000/ManageUsers	.	You'll

see	a	list	of	all	users	registered	for	the	application.

As	an	extra	challenge,	try	adding	more	administration	features	to

this	page.	For	example,	you	could	add	a	button	that	gives	an

administrator	the	ability	to	delete	a	user	account.

Check	for	authorization	in	a	view

93

Authorization	with	roles

The	 	[Authorize]		attribute	makes	it	easy	to	perform	an	authorization

check	in	a	controller	or	action	method,	but	what	if	you	need	to	check

authorization	in	a	view?	For	example,	it	would	be	nice	to	display	a

"Manage	users"	link	in	the	navigation	bar	if	the	logged-in	user	is	an

administrator.

You	can	inject	the	 	UserManager		directly	into	a	view	to	do	these	types	of

authorization	checks.	To	keep	your	views	clean	and	organized,	create	a

new	partial	view	that	will	add	an	item	to	the	navbar	in	the	layout:

Views/Shared/_AdminActionsPartial.cshtml

@using	Microsoft.AspNetCore.Identity

@using	AspNetCoreTodo.Models

@inject	SignInManager<ApplicationUser>	signInManager

@inject	UserManager<ApplicationUser>	userManager

@if	(signInManager.IsSignedIn(User))

{

				var	currentUser	=	await	UserManager.GetUserAsync(User);

				var	isAdmin	=	currentUser	!=	null

								&&	await	userManager.IsInRoleAsync(

												currentUser,

												Constants.AdministratorRole);

				if	(isAdmin)

				{

								<ul	class="nav	navbar-nav	navbar-right">

												<li>

																<a	asp-controller="ManageUsers"	

																			asp-action="Index">

																			Manage	Users

																</a>

												</li>

								</ul>

				}

}

94

Authorization	with	roles

It's	conventional	to	name	shared	partial	views	starting	with	an	 	_	

underscore,	but	it's	not	required.

This	partial	view	first	uses	the	 	SignInManager		to	quickly	determine

whether	the	user	is	logged	in.	If	they	aren't,	the	rest	of	the	view	code	can

be	skipped.	If	there	is	a	logged-in	user,	the	 	UserManager		is	used	to	look

up	their	details	and	perform	an	authorization	check	with

	IsInRoleAsync()	.	If	all	checks	succeed	and	the	user	is	an	adminstrator,	a

Manage	users	link	is	added	to	the	navbar.

To	include	this	partial	in	the	main	layout,	edit	 	_Layout.cshtml		and	add	it

in	the	navbar	section:

Views/Shared/_Layout.cshtml

<div	class="navbar-collapse	collapse">

				<ul	class="nav	navbar-nav">

								<!--	existing	code	here	-->

				</ul>

				@await	Html.PartialAsync("_LoginPartial")

				@await	Html.PartialAsync("_AdminActionsPartial")

</div>

When	you	log	in	with	an	administrator	account,	you'll	now	see	a	new

item	on	the	top	right:

95

More	resources

More	resources

ASP.NET	Core	Identity	helps	you	add	security	and	identity	features	like

login	and	registration	to	your	application.	The	 	dotnet	new		templates

give	you	pre-built	views	and	controllers	that	handle	these	common

scenarios	so	you	can	get	up	and	running	quickly.

There's	much	more	that	ASP.NET	Core	Identity	can	do,	such	as	password

reset	and	social	login.	The	documentation	available	at	http://docs.asp.net

is	a	fantastic	resource	for	learning	how	to	add	these	features.

Alternatives	to	ASP.NET	Core	Identity

ASP.NET	Core	Identity	isn't	the	only	way	to	add	identity	functionality.

Another	approach	is	to	use	a	cloud-hosted	identity	service	like	Azure

Active	Directory	B2C	or	Okta	to	handle	identity	for	your	application.	You

can	think	of	these	options	as	part	of	a	progression:

Do-it-yourself	security:	Not	recommended,	unless	you	are	a

security	expert!

ASP.NET	Core	Identity:	You	get	a	lot	of	code	for	free	with	the

templates,	which	makes	it	pretty	easy	to	get	started.	You'll	still	need

to	write	some	code	for	more	advanced	scenarios,	and	maintain	a

database	to	store	user	information.

Cloud-hosted	identity	services.	The	service	handles	both	simple	and

advanced	scenarios	(multi-factor	authentication,	account	recovery,

federation),	and	significantly	reduces	the	amount	of	code	you	need

to	write	and	maintain	in	your	application.	Plus,	sensitive	user	data

isn't	stored	in	your	own	database.

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More	resources

For	this	project,	ASP.NET	Core	Identity	is	a	great	fit.	For	more	complex

projects,	I'd	recommend	doing	some	research	and	experimenting	with

both	options	to	understand	which	is	best	for	your	use	case.

97

Automated	testing

Automated	testing

Writing	tests	is	an	important	part	of	building	any	application.	Testing

your	code	helps	you	find	and	avoid	bugs,	and	makes	it	easier	to	refactor

your	code	later	without	breaking	functionality	or	introducing	new

problems.

In	this	chapter	you'll	learn	how	to	write	both	unit	tests	and	integration

tests	that	exercise	your	ASP.NET	Core	application.	Unit	tests	are	small

tests	that	make	sure	a	single	method	or	chunk	of	logic	works	properly.

Integration	tests	(sometimes	called	functional	tests)	are	larger	tests	that

simulate	real-world	scenarios	and	test	multiple	layers	or	parts	of	your

application.

98

Unit	testing

Unit	testing

Unit	tests	are	small,	short	tests	that	check	the	behavior	of	a	single

method	or	class.	When	the	code	you're	testing	relies	on	other	methods

or	classes,	unit	tests	rely	on	mocking	those	other	classes	so	that	the	test

only	focuses	on	one	thing	at	a	time.

For	example,	the	 	TodoController		class	has	two	dependencies:	an

	ITodoItemService		and	the	 	UserManager	.	The	 	TodoItemService	,	in	turn,

depends	on	the	 	ApplicationDbContext	.	(The	idea	that	you	can	draw	a

line	from	 	TodoController		>	 	TodoItemService		>	 	ApplicationDbContext		is

called	a	dependency	graph).

When	the	application	runs	normally,	the	ASP.NET	Core	service	container

and	dependency	injection	system	injects	each	of	those	objects	into	the

dependency	graph	when	the	 	TodoController		or	the	 	TodoItemService		is

created.

When	you	write	a	unit	test,	on	the	other	hand,	you	have	to	handle	the

dependency	graph	yourself.	It's	typical	to	provide	test-only	or	"mocked"

versions	of	those	dependencies.	This	means	you	can	isolate	just	the	logic

in	the	class	or	method	you	are	testing.	(This	is	important!	If	you're	testing

a	service,	you	don't	want	to	also	be	accidentally	writing	to	your

database.)

Create	a	test	project

It's	a	best	practice	to	create	a	separate	project	for	your	tests,	so	they	are

kept	separate	from	your	application	code.	The	new	test	project	should

live	in	a	directory	that's	next	to	(not	inside)	your	main	project's	directory.

99

Unit	testing

If	you're	currently	in	your	project	directory,	 	cd		up	one	level.	(This	root

directory	will	also	be	called	 	AspNetCoreTodo	).	Then	use	this	command	to

scaffold	a	new	test	project:

dotnet	new	xunit	-o	AspNetCoreTodo.UnitTests

xUnit.NET	is	a	popular	test	framework	for	.NET	code	that	can	be	used	to

write	both	unit	and	integration	tests.	Like	everything	else,	it's	a	set	of

NuGet	packages	that	can	be	installed	in	any	project.	The	 	dotnet	new

xunit		template	already	includes	everything	you	need.

Your	directory	structure	should	now	look	like	this:

AspNetCoreTodo/

				AspNetCoreTodo/

								AspNetCoreTodo.csproj

								Controllers/

								(etc...)

				AspNetCoreTodo.UnitTests/

								AspNetCoreTodo.UnitTests.csproj

Since	the	test	project	will	use	the	classes	defined	in	your	main	project,

you'll	need	to	add	a	reference	to	the	 	AspNetCoreTodo		project:

dotnet	add	reference	../AspNetCoreTodo/AspNetCoreTodo.csproj

Delete	the	 	UnitTest1.cs		file	that's	automatically	created.	You're	ready

to	write	your	first	test.

If	you're	using	Visual	Studio	Code,	you	may	need	to	close	and

reopen	the	Visual	Studio	Code	window	to	get	code	completion

working	in	the	new	project.

Write	a	service	test

100

Unit	testing

Take	a	look	at	the	logic	in	the	 	AddItemAsync()		method	of	the

	TodoItemService	:

public	async	Task<bool>	AddItemAsync(

				TodoItem	newItem,	ApplicationUser	user)

{

				newItem.Id	=	Guid.NewGuid();

				newItem.IsDone	=	false;

				newItem.DueAt	=	DateTimeOffset.Now.AddDays(3);

				newItem.UserId	=	user.Id;

				_context.Items.Add(newItem);

				var	saveResult	=	await	_context.SaveChangesAsync();

				return	saveResult	==	1;

}

This	method	makes	a	number	of	decisions	or	assumptions	about	the	new

item	(in	other	words,	performs	business	logic	on	the	new	item)	before	it

actually	saves	it	to	the	database:

The	 	UserId		property	should	be	set	to	the	user's	ID

New	items	should	always	be	incomplete	( 	IsDone	=	false	)

The	title	of	the	new	item	should	be	copied	from	 	newItem.Title	

New	items	should	always	be	due	3	days	from	now

Imagine	if	you	or	someone	else	refactored	the	 	AddItemAsync()		method

and	forgot	about	part	of	this	business	logic.	The	behavior	of	your

application	could	change	without	you	realizing	it!	You	can	prevent	this	by

writing	a	test	that	double-checks	that	this	business	logic	hasn't	changed

(even	if	the	method's	internal	implementation	changes).

It	might	seem	unlikely	now	that	you	could	introduce	a	change	in

business	logic	without	realizing	it,	but	it	becomes	much	harder	to

keep	track	of	decisions	and	assumptions	in	a	large,	complex

project.	The	larger	your	project	is,	the	more	important	it	is	to	have

automated	checks	that	make	sure	nothing	has	changed!

101

Unit	testing

To	write	a	unit	test	that	will	verify	the	logic	in	the	 	TodoItemService	,

create	a	new	class	in	your	test	project:

AspNetCoreTodo.UnitTests/TodoItemServiceShould.cs

using	System;

using	System.Threading.Tasks;

using	AspNetCoreTodo.Data;

using	AspNetCoreTodo.Models;

using	AspNetCoreTodo.Services;

using	Microsoft.EntityFrameworkCore;

using	Xunit;

namespace	AspNetCoreTodo.UnitTests

{

				public	class	TodoItemServiceShould

				{

								[Fact]

								public	async	Task	AddNewItemAsIncompleteWithDueDate()

								{

												//	...

								}

				}

}

There	are	many	different	ways	of	naming	and	organizing	tests,	all

with	different	pros	and	cons.	I	like	postfixing	my	test	classes	with

	Should		to	create	a	readable	sentence	with	the	test	method	name,

but	feel	free	to	use	your	own	style!

The	 	[Fact]		attribute	comes	from	the	xUnit.NET	package,	and	it	marks

this	method	as	a	test	method.

The	 	TodoItemService		requires	an	 	ApplicationDbContext	,	which	is

normally	connected	to	your	database.	You	won't	want	to	use	that	for

tests.	Instead,	you	can	use	Entity	Framework	Core's	in-memory	database

provider	in	your	test	code.	Since	the	entire	database	exists	in	memory,

102

Unit	testing

it's	wiped	out	every	time	the	test	is	restarted.	And,	since	it's	a	proper

Entity	Framework	Core	provider,	the	 	TodoItemService		won't	know	the

difference!

Use	a	 	DbContextOptionsBuilder		to	configure	the	in-memory	database

provider,	and	then	make	a	call	to	 	AddItemAsync()	:

var	options	=	new	DbContextOptionsBuilder<ApplicationDbContext>()

				.UseInMemoryDatabase(databaseName:	"Test_AddNewItem").Options;

//	Set	up	a	context	(connection	to	the	"DB")	for	writing

using	(var	context	=	new	ApplicationDbContext(options))

{

				var	service	=	new	TodoItemService(context);

				var	fakeUser	=	new	ApplicationUser

				{

								Id	=	"fake-000",

								UserName	=	"[email protected]"

				};

				await	service.AddItemAsync(new	TodoItem

				{

								Title	=	"Testing?"

				},	fakeUser);

}

The	last	line	creates	a	new	to-do	item	called	 	Testing?	,	and	tells	the

service	to	save	it	to	the	(in-memory)	database.

To	verify	that	the	business	logic	ran	correctly,	write	some	more	code

below	the	existing	 	using		block:

//	Use	a	separate	context	to	read	data	back	from	the	"DB"

using	(var	context	=	new	ApplicationDbContext(options))

{

				var	itemsInDatabase	=	await	context

								.Items.CountAsync();

				Assert.Equal(1,	itemsInDatabase);

103

Unit	testing

				var	item	=	await	context.Items.FirstAsync();

				Assert.Equal("Testing?",	item.Title);

				Assert.Equal(false,	item.IsDone);

				//	Item	should	be	due	3	days	from	now	(give	or	take	a	second)

				var	difference	=	DateTimeOffset.Now.AddDays(3)	-	item.DueAt;

				Assert.True(difference	<	TimeSpan.FromSeconds(1));

}

The	first	assertion	is	a	sanity	check:	there	should	never	be	more	than	one

item	saved	to	the	in-memory	database.	Assuming	that's	true,	the	test

retrieves	the	saved	item	with	 	FirstAsync		and	then	asserts	that	the

properties	are	set	to	the	expected	values.

Both	unit	and	integration	tests	typically	follow	the	AAA	(Arrange-

Act-Assert)	pattern:	objects	and	data	are	set	up	first,	then	some

action	is	performed,	and	finally	the	test	checks	(asserts)	that	the

expected	behavior	occurred.

Asserting	a	datetime	value	is	a	little	tricky,	since	comparing	two	dates	for

equality	will	fail	if	even	the	millisecond	components	are	different.

Instead,	the	test	checks	that	the	 	DueAt		value	is	less	than	a	second	away

from	the	expected	value.

Run	the	test

On	the	terminal,	run	this	command	(make	sure	you're	still	in	the

	AspNetCoreTodo.UnitTests		directory):

dotnet	test

The	 	test		command	scans	the	current	project	for	tests	(marked	with

	[Fact]		attributes	in	this	case),	and	runs	all	the	tests	it	finds.	You'll	see

output	similar	to:

Starting	test	execution,	please	wait...

104

Unit	testing

	Discovering:	AspNetCoreTodo.UnitTests

	Discovered:		AspNetCoreTodo.UnitTests

	Starting:				AspNetCoreTodo.UnitTests

	Finished:				AspNetCoreTodo.UnitTests

Total	tests:	1.	Passed:	1.	Failed:	0.	Skipped:	0.

Test	Run	Successful.

Test	execution	time:	1.9074	Seconds

You	now	have	one	test	providing	test	coverage	of	the	 	TodoItemService	.

As	an	extra	challenge,	try	writing	unit	tests	that	ensure:

The	 	MarkDoneAsync()		method	returns	false	if	it's	passed	an	ID	that

doesn't	exist

The	 	MarkDoneAsync()		method	returns	true	when	it	makes	a	valid

item	as	complete

The	 	GetIncompleteItemsAsync()		method	returns	only	the	items

owned	by	a	particular	user

105

Integration	testing

Integration	testing

Compared	to	unit	tests,	integration	tests	are	much	larger	in	scope.

exercise	the	whole	application	stack.	Instead	of	isolating	one	class	or

method,	integration	tests	ensure	that	all	of	the	components	of	your

application	are	working	together	properly:	routing,	controllers,	services,

database	code,	and	so	on.

Integration	tests	are	slower	and	more	involved	than	unit	tests,	so	it's

common	for	a	project	to	have	lots	of	small	unit	tests	but	only	a	handful

of	integration	tests.

In	order	to	test	the	whole	stack	(including	controller	routing),	integration

tests	typically	make	HTTP	calls	to	your	application	just	like	a	web

browser	would.

To	write	integration	tests	that	make	HTTP	requests,	you	could	manually

start	your	application	and	tests	at	the	same	time,	and	write	your	tests	to

make	requests	to	 	http://localhost:5000	.	ASP.NET	Core	provides	a

nicer	way	to	host	your	application	for	testing,	however:	the	 	TestServer	

class.	 	TestServer		can	host	your	application	for	the	duration	of	the	test,

and	then	stop	it	automatically	when	the	test	is	complete.

Create	a	test	project

If	you're	currently	in	your	project	directory,	 	cd		up	one	level	to	the	root

	AspNetCoreTodo		directory.	Use	this	command	to	scaffold	a	new	test

project:

dotnet	new	xunit	-o	AspNetCoreTodo.IntegrationTests

Your	directory	structure	should	now	look	like	this:

106

Integration	testing

AspNetCoreTodo/

				AspNetCoreTodo/

								AspNetCoreTodo.csproj

								Controllers/

								(etc...)

				AspNetCoreTodo.UnitTests/

								AspNetCoreTodo.UnitTests.csproj

				AspNetCoreTodo.IntegrationTests/

								AspNetCoreTodo.IntegrationTests.csproj

If	you	prefer,	you	can	keep	your	unit	tests	and	integration	tests	in

the	same	project.	For	large	projects,	it's	common	to	split	them	up

so	it's	easy	to	run	them	separately.

Since	the	test	project	will	use	the	classes	defined	in	your	main	project,

you'll	need	to	add	a	reference	to	the	main	project:

dotnet	add	reference	../AspNetCoreTodo/AspNetCoreTodo.csproj

You'll	also	need	to	add	the	 	Microsoft.AspNetCore.TestHost		NuGet

package:

dotnet	add	package	Microsoft.AspNetCore.TestHost

Delete	the	 	UnitTest1.cs		file	that's	created	by	 	dotnet	new	.	You're	ready

to	write	an	integration	test.

Write	an	integration	test

There	are	a	few	things	that	need	to	be	configured	on	the	test	server

before	each	test.	Instead	of	cluttering	the	test	with	this	setup	code,	you

can	keep	this	setup	in	a	separate	class.	Create	a	new	class	called

	TestFixture	:

107

Integration	testing

AspNetCoreTodo.IntegrationTests/TestFixture.cs

using	System;

using	System.Collections.Generic;

using	System.IO;

using	System.Net.Http;

using	Microsoft.AspNetCore.Hosting;

using	Microsoft.AspNetCore.TestHost;

using	Microsoft.Extensions.Configuration;

namespace	AspNetCoreTodo.IntegrationTests

{

				public	class	TestFixture	:	IDisposable		

				{

								private	readonly	TestServer	_server;

								public	HttpClient	Client	{	get;	}

								public	TestFixture()

								{

												var	builder	=	new	WebHostBuilder()

																.UseStartup<AspNetCoreTodo.Startup>()

																.ConfigureAppConfiguration((context,	config)	=>

																{

																				config.SetBasePath(Path.Combine(

																								Directory.GetCurrentDirectory(),

																								"..\\..\\..\\..\\AspNetCoreTodo"));

																				config.AddJsonFile("appsettings.json");

																});

												_server	=	new	TestServer(builder);

												Client	=	_server.CreateClient();

												Client.BaseAddress	=	new	Uri("http://localhost:8888");

								}

								public	void	Dispose()

								{

												Client.Dispose();

												_server.Dispose();

								}

				}

}

108

Integration	testing

This	class	takes	care	of	setting	up	a	 	TestServer	,	and	will	help	keep	the

tests	themselves	clean	and	tidy.

Now	you're	(really)	ready	to	write	an	integration	test.	Create	a	new	class

called	 	TodoRouteShould	:

AspNetCoreTodo.IntegrationTests/TodoRouteShould.cs

using	System.Net;

using	System.Net.Http;

using	System.Threading.Tasks;

using	Xunit;

namespace	AspNetCoreTodo.IntegrationTests

{

				public	class	TodoRouteShould	:	IClassFixture<TestFixture>

				{

								private	readonly	HttpClient	_client;

								public	TodoRouteShould(TestFixture	fixture)

								{

												_client	=	fixture.Client;

								}

								[Fact]

								public	async	Task	ChallengeAnonymousUser()

								{

												//	Arrange

												var	request	=	new	HttpRequestMessage(

																HttpMethod.Get,	"/todo");

												//	Act:	request	the	/todo	route

												var	response	=	await	_client.SendAsync(request);

												//	Assert:	the	user	is	sent	to	the	login	page

												Assert.Equal(

																HttpStatusCode.Redirect,

																response.StatusCode);

												Assert.Equal(

																"http://localhost:8888/Account"	+

109

Integration	testing

																"/Login?ReturnUrl=%2Ftodo",

																response.Headers.Location.ToString());

								}

				}

}

This	test	makes	an	anonymous	(not-logged-in)	request	to	the	 	/todo	

route	and	verifies	that	the	browser	is	redirected	to	the	login	page.

This	scenario	is	a	good	candidate	for	an	integration	test,	because	it

involves	multiple	components	of	the	application:	the	routing	system,	the

controller,	the	fact	that	the	controller	is	marked	with	 	[Authorize]	,	and

so	on.	It's	also	a	good	test	because	it	ensures	you	won't	ever	accidentally

remove	the	 	[Authorize]		attribute	and	make	the	to-do	view	accessible

to	everyone.

Run	the	test

Run	the	test	in	the	terminal	with	 	dotnet	test	.	If	everything's	working

right,	you'll	see	a	success	message:

Starting	test	execution,	please	wait...

	Discovering:	AspNetCoreTodo.IntegrationTests

	Discovered:		AspNetCoreTodo.IntegrationTests

	Starting:				AspNetCoreTodo.IntegrationTests

	Finished:				AspNetCoreTodo.IntegrationTests

Total	tests:	1.	Passed:	1.	Failed:	0.	Skipped:	0.

Test	Run	Successful.

Test	execution	time:	2.0588	Seconds

Wrap	up

110

Integration	testing

Testing	is	a	broad	topic,	and	there's	much	more	to	learn.	This	chapter

doesn't	touch	on	UI	testing	or	testing	frontend	(JavaScript)	code,	which

probably	deserve	entire	books	of	their	own.	You	should,	however,	have

the	skills	and	base	knowledge	you	need	to	learn	more	about	testing	and

to	practice	writing	tests	for	your	own	applications.

The	ASP.NET	Core	documentation	(https://docs.asp.net)	and	Stack

Overflow	are	great	resources	for	learning	more	and	finding	answers

when	you	get	stuck.

111

Deploy	the	application

Deploy	the	application

You've	come	a	long	way,	but	you're	not	quite	done	yet.	Once	you've

created	a	great	application,	you	need	to	share	it	with	the	world!

Because	ASP.NET	Core	applications	can	run	on	Windows,	Mac,	or	Linux,

there	are	a	number	of	different	ways	you	can	deploy	your	application.	In

this	chapter,	I'll	show	you	the	most	common	(and	easiest)	ways	to	go	live.

Deployment	options

ASP.NET	Core	applications	are	typically	deployed	to	one	of	these

environments:

A	Docker	host.	Any	machine	capable	of	hosting	Docker	containers

can	be	used	to	host	an	ASP.NET	Core	application.	Creating	a	Docker

image	is	a	very	quick	way	to	get	your	application	deployed,

especially	if	you're	familiar	with	Docker.	(If	you're	not,	don't	worry!

I'll	cover	the	steps	later.)

Azure.	Microsoft	Azure	has	native	support	for	ASP.NET	Core

applications.	If	you	have	an	Azure	subscription,	you	just	need	to

create	a	Web	App	and	upload	your	project	files.	I'll	cover	how	to	do

this	with	the	Azure	CLI	in	the	next	section.

Linux	(with	Nginx).	If	you	don't	want	to	go	the	Docker	route,	you

can	still	host	your	application	on	any	Linux	server	(this	includes

Amazon	EC2	and	DigitalOcean	virtual	machines).	It's	typical	to	pair

ASP.NET	Core	with	the	Nginx	reverse	proxy.	(More	about	Nginx

below.)

112

Deploy	the	application

Windows.	You	can	use	the	IIS	web	server	on	Windows	to	host

ASP.NET	Core	applications.	It's	usually	easier	(and	cheaper)	to	just

deploy	to	Azure,	but	if	you	prefer	managing	Windows	servers

yourself,	it'll	work	just	fine.

Kestrel	and	reverse	proxies

If	you	don't	care	about	the	guts	of	hosting	ASP.NET	Core

applications	and	just	want	the	step-by-step	instructions,	feel	free

to	skip	to	one	of	the	next	two	sections.

ASP.NET	Core	includes	a	fast,	lightweight	web	server	called	Kestrel.	It's

the	server	you've	been	using	every	time	you	ran	 	dotnet	run		and

browsed	to	 	http://localhost:5000	.	When	you	deploy	your	application

to	a	production	environment,	it'll	still	use	Kestrel	behind	the	scenes.

However,	it's	recommended	that	you	put	a	reverse	proxy	in	front	of

Kestrel,	because	Kestrel	doesn't	yet	have	load	balancing	and	other

features	that	more	mature	web	servers	have.

On	Linux	(and	in	Docker	containers),	you	can	use	Nginx	or	the	Apache

web	server	to	receive	incoming	requests	from	the	internet	and	route

them	to	your	application	hosted	with	Kestrel.	If	you're	on	Windows,	IIS

does	the	same	thing.

If	you're	using	Azure	to	host	your	application,	this	is	all	done	for	you

automatically.	I'll	cover	setting	up	Nginx	as	a	reverse	proxy	in	the	Docker

section.

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Deploy	to	Azure

Deploy	to	Azure

Deploying	your	ASP.NET	Core	application	to	Azure	only	takes	a	few

steps.	You	can	do	it	through	the	Azure	web	portal,	or	on	the	command

line	using	the	Azure	CLI.	I'll	cover	the	latter.

What	you'll	need

Git	(use	 	git	--version		to	make	sure	it's	installed)

The	Azure	CLI	(follow	the	install	instructions	at

https://github.com/Azure/azure-cli)

An	Azure	subscription	(the	free	subscription	is	fine)

A	deployment	configuration	file	in	your	project	root

Create	a	deployment	configuration	file

Since	there	are	multiple	projects	in	your	directory	structure	(the	web

application,	and	two	test	projects),	Azure	won't	know	which	one	to

publish.	To	fix	this,	create	a	file	called	 	.deployment		at	the	very	top	of

your	directory	structure:

.deployment

[config]

project	=	AspNetCoreTodo/AspNetCoreTodo.csproj

Make	sure	you	save	the	file	as	 	.deployment		with	no	other	parts	to	the

name.	(On	Windows,	you	may	need	to	put	quotes	around	the	filename,

like	 	".deployment"	,	to	prevent	a	 	.txt		extension	from	being	added.)

If	you	 	ls		or	 	dir		in	your	top-level	directory,	you	should	see	these

items:

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Deploy	to	Azure

.deployment

AspNetCoreTodo

AspNetCoreTodo.IntegrationTests

AspNetCoreTodo.UnitTests

Set	up	the	Azure	resources

If	you	just	installed	the	Azure	CLI	for	the	first	time,	run

az	login

and	follow	the	prompts	to	log	in	on	your	machine.	Then,	create	a	new

Resource	Group	for	this	application:

az	group	create	-l	westus	-n	AspNetCoreTodoGroup

This	creates	a	Resource	Group	in	the	West	US	region.	If	you're	located

far	away	from	the	western	US,	use	 	az	account	list-locations		to	get	a

list	of	locations	and	find	one	closer	to	you.

Next,	create	an	App	Service	plan	in	the	group	you	just	created:

az	appservice	plan	create	-g	AspNetCoreTodoGroup	-n	AspNetCoreTodo

Plan	--sku	F1

F1	is	the	free	app	plan.	If	you	want	to	use	a	custom	domain	name

with	your	app,	use	the	D1	($10/month)	plan	or	higher.

Now	create	a	Web	App	in	the	App	Service	plan:

az	webapp	create	-g	AspNetCoreTodoGroup	-p	AspNetCoreTodoPlan	-n	M

yTodoApp

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Deploy	to	Azure

The	name	of	the	app	( 	MyTodoApp		above)	must	be	globally	unique	in

Azure.	Once	the	app	is	created,	it	will	have	a	default	URL	in	the	format:

http://mytodoapp.azurewebsites.net

Deploy	your	project	files	to	Azure

You	can	use	Git	to	push	your	application	files	up	to	the	Azure	Web	App.

If	your	local	directory	isn't	already	tracked	as	a	Git	repo,	run	these

commands	to	set	it	up:

git	init

git	add	.

git	commit	-m	"First	commit!"

Next,	create	an	Azure	username	and	password	for	deployment:

az	webapp	deployment	user	set	--user-name	nate

Follow	the	instructions	to	create	a	password.	Then	use	 	config-local-

git		to	spit	out	a	Git	URL:

az	webapp	deployment	source	config-local-git	-g	AspNetCoreTodoGrou

p	-n	MyTodoApp	--out	tsv

https://[email protected]/MyTodoApp.git

Copy	the	URL	to	the	clipboard,	and	use	it	to	add	a	Git	remote	to	your

local	repository:

git	remote	add	azure	<paste>

You	only	need	to	do	these	steps	once.	Now,	whenever	you	want	to	push

your	application	files	to	Azure,	check	them	in	with	Git	and	run

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Deploy	to	Azure

git	push	azure	master

You'll	see	a	stream	of	log	messages	as	the	application	is	deployed	to

Azure.

When	it's	complete,	browse	to	http://yourappname.azurewebsites.net	to

check	out	the	app!

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Deploy	with	Docker

Deploy	with	Docker

If	you	aren't	using	a	platform	like	Azure,	containerization	technologies

like	Docker	can	make	it	easy	to	deploy	web	applications	to	your	own

servers.	Instead	of	spending	time	configuring	a	server	with	the

dependencies	it	needs	to	run	your	app,	copying	files,	and	restarting

processes,	you	can	simply	create	a	Docker	image	that	describes

everything	your	app	needs	to	run,	and	spin	it	up	as	a	container	on	any

Docker	host.

Docker	can	make	scaling	your	app	across	multiple	servers	easier,	too.

Once	you	have	an	image,	using	it	to	create	1	container	is	the	same

process	as	creating	100	containers.

Before	you	start,	you	need	the	Docker	CLI	installed	on	your

development	machine.	Search	for	"get	docker	for	(mac/windows/linux)"

and	follow	the	instructions	on	the	official	Docker	website.	You	can	verify

that	it's	installed	correctly	with

docker	version

Add	a	Dockerfile

The	first	thing	you'll	need	is	a	Dockerfile,	which	is	like	a	recipe	that	tells

Docker	what	your	application	needs	to	build	and	run.

Create	a	file	called	 	Dockerfile		(no	extension)	in	the	root,	top-level

	AspNetCoreTodo		folder.	Open	it	in	your	favorite	editor.	Write	the

following	line:

FROM	microsoft/dotnet:2.0-sdk	AS	build

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Deploy	with	Docker

This	tells	Docker	to	use	the	 	microsoft/dotnet:2.0-sdk		image	as	a

starting	point.	This	image	is	published	by	Microsoft	and	contains	the

tools	and	dependencies	you	need	to	execute	 	dotnet	build		and	compile

your	application.	By	using	this	pre-built	image	as	a	starting	point,	Docker

can	optimize	the	image	produced	for	your	app	and	keep	it	small.

Next,	add	this	line:

COPY	AspNetCoreTodo/*.csproj	./app/AspNetCoreTodo/

The	 	COPY		command	copies	the	 	.csproj		project	file	into	the	image	at

the	path	 	/app/AspNetCoreTodo/	.	Note	that	none	of	the	actual	code	( 	.cs	

files)	have	been	copied	into	the	image	yet.	You'll	see	why	in	a	minute.

WORKDIR	/app/AspNetCoreTodo

RUN	dotnet	restore

	WORKDIR		is	the	Docker	equivalent	of	 	cd	.	This	means	any	commands

executed	next	will	run	from	inside	the	 	/app/AspNetCoreTodo		directory

that	the	 	COPY		command	created	in	the	last	step.

Running	the	 	dotnet	restore		command	restores	the	NuGet	packages

that	the	application	needs,	defined	in	the	 	.csproj		file.	By	restoring

packages	inside	the	image	before	adding	the	rest	of	the	code,	Docker	is

able	to	cache	the	restored	packages.	Then,	if	you	make	code	changes

(but	don't	change	the	packages	defined	in	the	project	file),	rebuilding	the

Docker	image	will	be	super	fast.

Now	it's	time	to	copy	the	rest	of	the	code	and	compile	the	application:

COPY	AspNetCoreTodo/.	./AspNetCoreTodo/

RUN	dotnet	publish	-o	out	/p:PublishWithAspNetCoreTargetManifest="

false"

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Deploy	with	Docker

The	 	dotnet	publish		command	compiles	the	project,	and	the	 	-o	out	

flag	puts	the	compiled	files	in	a	directory	called	 	out	.

These	compiled	files	will	be	used	to	run	the	application	with	the	final	few

commands:

FROM	microsoft/dotnet:2.0-runtime	AS	runtime

ENV	ASPNETCORE_URLS	http://+:80

WORKDIR	/app

COPY	--from=build	/app/AspNetCoreTodo/out	./

ENTRYPOINT	["dotnet",	"AspNetCoreTodo.dll"]

The	 	FROM		command	is	used	again	to	select	a	smaller	image	that	only	has

the	dependencies	needed	to	run	the	application.	The	 	ENV		command	is

used	to	set	environment	variables	in	the	container,	and	the

	ASPNETCORE_URLS		environment	variable	tells	ASP.NET	Core	which

network	interface	and	port	it	should	bind	to	(in	this	case,	port	80).

The	 	ENTRYPOINT		command	lets	Docker	know	that	the	container	should

be	started	as	an	executable	by	running	 	dotnet	AspNetCoreTodo.dll	.	This

tells	 	dotnet		to	start	up	your	application	from	the	compiled	file	created

by	 	dotnet	publish		earlier.	(When	you	do	 	dotnet	run		during

development,	you're	accomplishing	the	same	thing	in	one	step.)

The	full	Dockerfile	looks	like	this:

Dockerfile

FROM	microsoft/dotnet:2.0-sdk	AS	build

COPY	AspNetCoreTodo/*.csproj	./app/AspNetCoreTodo/

WORKDIR	/app/AspNetCoreTodo

RUN	dotnet	restore

COPY	AspNetCoreTodo/.	./

RUN	dotnet	publish	-o	out	/p:PublishWithAspNetCoreTargetManifest="

false"

FROM	microsoft/dotnet:2.0-runtime	AS	runtime

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Deploy	with	Docker

ENV	ASPNETCORE_URLS	http://+:80

WORKDIR	/app

COPY	--from=build	/app/AspNetCoreTodo/out	./

ENTRYPOINT	["dotnet",	"AspNetCoreTodo.dll"]

Create	an	image

Make	sure	the	Dockerfile	is	saved,	and	then	use	 	docker	build		to	create

an	image:

docker	build	-t	aspnetcoretodo	.

Don't	miss	the	trailing	period!	That	tells	Docker	to	look	for	a	Dockerfile

in	the	current	directory.

Once	the	image	is	created,	you	can	run	 	docker	images		to	to	list	all	the

images	available	on	your	local	machine.	To	test	it	out	in	a	container,	run

docker	run	--name	aspnetcoretodo_sample	--rm	-it	-p	8080:80	aspnet

coretodo

The	 	-it		flag	tells	Docker	to	run	the	container	in	interactive	mode

(outputting	to	the	terminal,	as	opposed	to	running	in	the	background).

When	you	want	to	stop	the	container,	press	Control-C.

Remember	the	 	ASPNETCORE_URLS		variable	that	told	ASP.NET	Core	to

listen	on	port	80?	The	 	-p	8080:80		option	tells	Docker	to	map	port	8080

on	your	machine	to	the	container's	port	80.	Open	up	your	browser	and

navigate	to	http://localhost:8080	to	see	the	application	running	in	the

container!

Set	up	Nginx

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Deploy	with	Docker

At	the	beginning	of	this	chapter,	I	mentioned	that	you	should	use	a

reverse	proxy	like	Nginx	to	proxy	requests	to	Kestrel.	You	can	use

Docker	for	this,	too.

The	overall	architecture	will	consist	of	two	containers:	an	Nginx

container	listening	on	port	80,	forwarding	requests	to	the	container	you

just	built	that	hosts	your	application	with	Kestrel.

The	Nginx	container	needs	its	own	Dockerfile.	To	keep	it	from

conflicting	with	the	Dockerfile	you	just	created,	make	a	new	directory	in

the	web	application	root:

mkdir	nginx

Create	a	new	Dockerfile	and	add	these	lines:

nginx/Dockerfile

FROM	nginx

COPY	nginx.conf	/etc/nginx/nginx.conf

Next,	create	an	 	nginx.conf		file:

nginx/nginx.conf

events	{	worker_connections	1024;	}

http	{

				server	{

								listen	80;

								location	/	{

										proxy_pass	http://kestrel:80;

										proxy_http_version	1.1;

										proxy_set_header	Upgrade	$http_upgrade;

										proxy_set_header	Connection	'keep-alive';

										proxy_set_header	Host	$host;

										proxy_cache_bypass	$http_upgrade;

								}

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Deploy	with	Docker

				}

}

This	configuration	file	tells	Nginx	to	proxy	incoming	requests	to

	http://kestrel:80	.	(You'll	see	why	 	kestrel		works	as	a	hostname	in	a

moment.)

When	you	make	deploy	your	application	to	a	production

environment,	you	should	add	the	 	server_name		directive	and

validate	and	restrict	the	host	header	to	known	good	values.	For

more	information,	see:

https://github.com/aspnet/Announcements/issues/295

Set	up	Docker	Compose

There's	one	more	file	to	create.	Up	in	the	root	directory,	create	 	docker-

compose.yml	:

docker-compose.yml

nginx:

				build:	./nginx

				links:

								-	kestrel:kestrel

				ports:

								-	"80:80"

kestrel:

				build:	.

				ports:

								-	"80"

Docker	Compose	is	a	tool	that	helps	you	create	and	run	multi-container

applications.	This	configuration	file	defines	two	containers:	 	nginx		from

the	 	./nginx/Dockerfile		recipe,	and	 	kestrel		from	the	 	./Dockerfile	

recipe.	The	containers	are	explicitly	linked	together	so	they	can

communicate.

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Deploy	with	Docker

You	can	try	spinning	up	the	entire	multi-container	application	by	running:

docker-compose	up

Try	opening	a	browser	and	navigating	to	http://localhost	(port	80,	not

8080!).	Nginx	is	listening	on	port	80	(the	default	HTTP	port)	and	proxying

requests	to	your	ASP.NET	Core	application	hosted	by	Kestrel.

Set	up	a	Docker	server

Specific	setup	instructions	are	outside	the	scope	of	this	book,	but	any

modern	flavor	of	Linux	(like	Ubuntu)	can	be	used	to	set	up	a	Docker	host.

For	example,	you	could	create	a	virtual	machine	with	Amazon	EC2,	and

install	the	Docker	service.	You	can	search	for	"amazon	ec2	set	up

docker"	(for	example)	for	instructions.

I	like	using	DigitalOcean	because	they've	made	it	really	easy	to	get

started.	DigitalOcean	has	both	a	pre-built	Docker	virtual	machine,	and	in-

depth	tutorials	for	getting	Docker	up	and	running	(search	for

"digitalocean	docker").

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Conclusion

Conclusion

Thanks	for	making	it	to	the	end	of	the	Little	ASP.NET	Core	Book!	If	this

book	was	helpful	(or	not),	I'd	love	to	hear	your	thoughts.	Send	me	your

comments	via	Twitter:	https://twitter.com/nbarbettini

How	to	learn	more

There's	a	lot	more	that	ASP.NET	Core	can	do	that	couldn't	fit	in	this

short	book,	including

Building	RESTful	APIs	and	microservices

Using	ASP.NET	Core	with	single-page	apps	like	Angular	and	React

Razor	Pages

Bundling	and	minifying	static	assets

WebSockets	and	SignalR

There	are	a	number	of	ways	you	can	learn	more:

The	ASP.NET	Core	documentation.	The	official	ASP.NET	Core

documentation	at	http://docs.asp.net	contains	a	number	of	in-depth

tutorials	covering	many	of	these	topics.	I'd	highly	recommend	it!

ASP.NET	Core	in	Action.	This	book	by	Andrew	Lock	is	a

comprehensive,	deep	dive	into	ASP.NET	Core.	You	can	get	it	from

Amazon	or	a	local	bookstore.

Courses	on	LinkedIn	Learning	and	Pluralsight.	If	you	learn	best	from

videos,	there	are	fantastic	courses	available	on	Pluralsight	and

LinkedIn	Learning	(including	some	by	yours	truly).	If	you	don't	have

an	account	and	need	a	coupon,	send	me	an	email:

[email protected].

125

Conclusion

Nate's	blog.	I	also	write	about	ASP.NET	Core	and	more	on	my	blog

at	https://www.recaffeinate.co.

Happy	coding!

About	the	author

Hey,	I'm	Nate!	I	wrote	the	Little	ASP.NET	Core	Book	in	a	long,	caffeine-

fueled	weekend	because	I	love	the	.NET	community	and	wanted	to	give

back	in	my	own	little	way.	I	hope	it	helped	you	learn	something	new!

You	can	stay	in	touch	with	me	on	Twitter	(@nbarbettini)	or	on	my	blog

(https://www.recaffeinate.co).	You	can	also	reach	me	via	email	at

[email protected].

Special	thanks

To	Jennifer,	who	always	supports	my	crazy	ideas.

To	the	following	contributors	who	improved	the	Little	ASP.NET	Core

Book:

0xNF

Matt	Welke

To	these	amazing	polyglot	programmers	who	translated	the	Little

ASP.NET	Core	Book:

sahinyanlik	(Turkish)

windsting,	yuyi	(Simplified	Chinese)

Changelog

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Conclusion

The	full,	detailed	changelog	is	always	available	here:

https://github.com/nbarbettini/little-aspnetcore-book/releases

1.1.0	(2018-05-03):	Significantly	reworked	the	Add	more	features	chapter

to	use	MVC	thorough	the	whole	stack	and	remove	the	AJAX	pattern.

Removed	Facebook	login	to	simplify	the	security	chapter	and	streamline

testing	and	deployment.	Updated	the	Docker	instructions	to	reflect	the

latest	best	practices.	Fixed	typos	and	added	suggestions	from	readers.

The	book	also	sports	a	new,	improved	cover	design!

1.0.4	(2018-01-15):	Added	explanation	of	service	container	lifecycles,

clarified	server	ports	and	the	-o	flag,	and	removed	semicolons	after	Razor

directives.	Corrected	Chinese	translation	author	credit.	Fixed	other	small

typos	and	issues	noticed	by	readers.

1.0.3	(2017-11-13):	Typo	fixes	and	small	improvements	suggested	by

readers.

1.0.2	(2017-10-20):	More	bug	fixes	and	small	improvements.	Added	link

to	translations.

1.0.1	(2017-09-23):	Bug	fixes	and	small	improvements.

1.0.0	(2017-09-18):	Initial	release.

127