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/intro%20to%20asp.net%20mvc%204%20with%20visual%20studio%20-%20beta.pdf.txt
Intr | |
Visu | |
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ual S | |
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Studio | |
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o (Be | |
T MV | |
eta) | |
VC 4 w | |
with | |
Rick A | |
Anderso | |
on and S | |
Scott Ha | |
anselma | |
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Summa | |
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orial will te | |
ach you the | |
e basics of | |
building an | |
n ASP.NET M | |
MVC Web | |
applicat | |
ion using M | |
Microsoft Vi | |
isual Studio | |
o 11 Express | |
s Beta for W | |
Web, which | |
is a free | |
version o | |
of Microsof | |
ft Visual Stu | |
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Categor | |
ry: Step-By | |
-Step | |
Applies | |
to: ASP.NE | |
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Studio 11 B | |
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Source: | |
ASP.NET si | |
te (link to s | |
source cont | |
tent) | |
E-book | |
publicatio | |
on date: Ma | |
ay 2012 | |
115 pag | |
es | |
Copyright © 2012 by Microsoft Corporation | |
All rights reserved. No part of the contents of this book may be reproduced or transmitted in any form or by any means | |
without the written permission of the publisher. | |
Microsoft and the trademarks listed at | |
http://www.microsoft.com/about/legal/en/us/IntellectualProperty/Trademarks/EN-US.aspx are trademarks of the | |
Microsoft group of companies. All other marks are property of their respective owners. | |
The example companies, organizations, products, domain names, email addresses, logos, people, places, and events | |
depicted herein are fictitious. No association with any real company, organization, product, domain name, email address, | |
logo, person, place, or event is intended or should be inferred. | |
This book expresses the author’s views and opinions. The information contained in this book is provided without any | |
express, statutory, or implied warranties. Neither the authors, Microsoft Corporation, nor its resellers, or distributors will | |
be held liable for any damages caused or alleged to be caused either directly or indirectly by this book. | |
Contents | |
Getting Started ........................................................................................................................................ 3 | |
What You'll Build ........................................................................................................................... 3 | |
Skills You'll Learn ........................................................................................................................... 5 | |
Getting Started .............................................................................................................................. 6 | |
Creating Your First Application .................................................................................................... 7 | |
Adding a Controller ............................................................................................................................ 13 | |
Adding a View ..................................................................................................................................... 20 | |
Changing Views and Layout Pages ............................................................................................ 25 | |
Passing Data from the Controller to the View ........................................................................... 31 | |
Adding a Model .................................................................................................................................. 37 | |
Adding Model Classes................................................................................................................. 37 | |
Creating a Connection String and Working with SQL Server LocalDB .................................... 41 | |
Accessing Your Model's Data from a Controller ............................................................................... 43 | |
Creating a Movie ......................................................................................................................... 46 | |
Examining the Generated Code.................................................................................................. 48 | |
Strongly Typed Models and the @model Keyword .................................................................. 49 | |
Working with SQL Server LocalDB ............................................................................................. 53 | |
Examining the Edit Methods and Edit View ...................................................................................... 58 | |
Processing the POST Request ..................................................................................................... 65 | |
Adding a Search Method and Search View ............................................................................... 67 | |
Displaying the SearchIndex Form ............................................................................................... 67 | |
Adding Search by Genre ............................................................................................................. 77 | |
Adding Markup to the SearchIndex View to Support Search by Genre .................................. 79 | |
Adding a New Field to the Movie Model and Table ......................................................................... 80 | |
Adding a Rating Property to the Movie Model ......................................................................... 80 | |
Managing Model and Database Schema Differences ............................................................... 82 | |
Automatically Re-Creating the Database on Model Changes .................................................. 85 | |
Adding Validation to the Model ........................................................................................................ 95 | |
Keeping Things DRY .................................................................................................................... 95 | |
Adding Validation Rules to the Movie Model ........................................................................... 95 | |
Validation Error UI in ASP.NET MVC .......................................................................................... 97 | |
How Validation Occurs in the Create View and Create Action Method ................................ 100 | |
Adding Formatting to the Movie Model.................................................................................. 108 | |
Examining the Details and Delete Methods .................................................................................... 111 | |
Examining the Details and Delete Methods ............................................................................ 111 | |
Wrapping Up ............................................................................................................................. 113 | |
Getting Started | |
By Rick Anderson and Scott Hanselman | |
This tutorial will teach you the basics of building an ASP.NET MVC Web application using Microsoft Visual | |
Studio 11 Express Beta for Web, which is a free version of Microsoft Visual Studio. Before you start, make sure | |
you've installed the prerequisites listed below. You can install all of them by clicking the following link: Web | |
Platform Installer. | |
If you're using Visual Studio 11 Beta instead of Visual Studio 11 Express Beta for Web , install the prerequisites | |
by clicking the following link: Web Platform Installer | |
A Visual Web Developer project with C# source code is available to accompany this topic. Download the C# | |
version. | |
What You'll Build | |
You'll implement a simple movie-listing application that supports creating, editing, searching and listing movies | |
from a database. Below are two screenshots of the application you’ll build. It includes a page that displays a list | |
of movies from a database: | |
The application also lets you add, edit, and delete movies, as well as see details about individual ones. All data- | |
entry scenarios include validation to ensure that the data stored in the database is correct. | |
Skills You'll Learn | |
Here's what you'll learn: | |
• How to create a new ASP.NET MVC project. | |
• How to create ASP.NET MVC controllers and views. | |
• How to create a new database using the Entity Framework Code First paradigm. | |
• How to retrieve and display data. | |
• How to edit data and enable data validation. | |
Getting Started | |
Start by running Visual Web Developer 11 Express Beta("Visual Web Developer" or VWD for short) and select | |
New Project from the Start page. | |
Visual Web Developer is an IDE, or integrated development environment. Just like you use Microsoft Word to | |
write documents, you'll use an IDE to create applications. In Visual Web Developer there's a toolbar along the | |
top showing various options available to you. There's also a menu that provides another way to perform tasks | |
in the IDE. (For example, instead of selecting New Project from the Start page, you can use the menu and | |
select File>New Project.) | |
Creating Your First Application | |
You can create applications using either Visual Basic or Visual C# as the programming language. Select Visual | |
C# on the left and then select ASP.NET MVC 4 Web Application. Name your project "MvcMovie" and then | |
click OK. | |
In the New ASP.NET MVC 4 Project dialog box, select Internet Application. LeaveRazor as the default view | |
engine. | |
Click OK. Visual Web Developer used a default template for the ASP.NET MVC project you just created, so you | |
have a working application right now without doing anything! This is a simple "Hello World!" project, and it's a | |
good place to start your application. | |
From the Debug menu, select Start Debugging. | |
Notice that the keyboard shortcut to start debugging is F5. | |
F5 causes Visual Web Developer to start IIS Express and run your web application. Visual Web Developer then | |
launches a browser and opens the application's home page. Notice that the address bar of the browser says | |
localhost and not something like example.com. That's becauselocalhost always points to your own local | |
computer, which in this case is running the application you just built. When Visual Web Developer runs a web | |
project, a random port is used for the web server. In the image below, the port number is 41788. When you run | |
the application, you'll probably see a different port number. | |
Right out of the box this default template gives you Home, Contact and About pages. It also provides support | |
to register and log in, and links to Facebook and Twitter. The next step is to change how this application works | |
and learn a little bit about ASP.NET MVC. Close your browser and let's change some code. | |
Adding a Controller | |
MVC stands formodel-view-controller. MVC is a pattern for developing applications that are well | |
architected, testable and easy to maintain. MVC-based applications contain: | |
• Models: Classes that represent the data of the application and that use validation logic to enforce | |
business rules for that data. | |
• Views: Template files that your application uses to dynamically generate HTML responses. | |
• Controllers: Classes that handle incoming browser requests, retrieve model data, and then specify | |
view templates that return a response to the browser. | |
We'll be covering all these concepts in this tutorial series and show you how to use them to build an | |
application. | |
Let's begin by creating a controller class. InSolution Explorer, right-click theControllersfolder and then | |
selectAdd Controller. | |
Name your new controller "HelloWorldController". Leave the default template asEmpty controllerand | |
clickAdd. | |
Notice inSolution Explorerthat a new file has been created namedHelloWorldController.cs. The file is | |
open in the IDE. | |
Replace the contents of the file with the following code. | |
usingSystem.Web; | |
usingSystem.Web.Mvc; | |
namespaceMvcMovie.Controllers | |
{ | |
publicclassHelloWorldController:Controller | |
{ | |
// | |
// GET: /HelloWorld/ | |
publicstringIndex() | |
{ | |
return"This is my <b>default</b> action..."; | |
} | |
// | |
// GET: /HelloWorld/Welcome/ | |
publicstringWelcome() | |
{ | |
return"This is the Welcome action method..."; | |
} | |
} | |
} | |
The controller methods will return a string of HTML as an example. The controller is | |
namedHelloWorldControllerand the first method above is namedIndex. Let’s invoke it from a browser. | |
Run the application (press F5 or Ctrl+F5). In the browser, append "HelloWorld" to the path in the address | |
bar. (For example, in the illustration below, it'shttp://localhost:1234/HelloWorld.) The page in the browser | |
will look like the following screenshot. In the method above, the code returned a string directly. You told | |
the system to just return some HTML, and it did! | |
ASP.NET MVC invokes different controller classes (and different action methods within them) depending | |
on the incoming URL. The default URL routing logic used by ASP.NET MVC uses a format like this to | |
determine what code to invoke: | |
/[Controller]/[ActionName]/[Parameters] | |
The first part of the URL determines the controller class to execute. So/HelloWorldmaps to the | |
HelloWorldControllerclass. The second part of the URL determines the action method on the class to | |
execute. So/HelloWorld/Indexwould cause theIndexmethod of theHelloWorldControllerclass to | |
execute. Notice that we only had to browse to/HelloWorldand theIndexmethod was used by default. This | |
is because a method named Indexis the default method that will be called on a controller if one is not | |
explicitly specified. | |
Browse tohttp://localhost:xxxx/HelloWorld/Welcome. TheWelcomemethod runs and returns the string "This | |
is the Welcome action method...". The default MVC mapping | |
is/[Controller]/[ActionName]/[Parameters]. For this URL, the controller | |
isHelloWorldandWelcomeis the action method. You haven't used the[Parameters]part of the URL yet. | |
Let's modify the example slightly so that you can pass some parameter information from the URL to the | |
controller (for example,/HelloWorld/Welcome?name=Scott&numtimes=4). Change yourWelcomemethod | |
to include two parameters as shown below. Note that the code uses the C# optional-parameter feature to | |
indicate that the numTimesparameter should default to 1 if no value is passed for that parameter. | |
publicstringWelcome(string name,int numTimes =1){ | |
returnHttpUtility.HtmlEncode("Hello "+ name +", NumTimes is: "+ numTimes); | |
} | |
Run your application and browse to the example URL | |
(http://localhost:xxxx/HelloWorld/Welcome?name=Scott&numtimes=4). You can try different values | |
fornameandnumtimesin the URL. The ASP.NET MVC model binding system automatically maps the named | |
parameters from the query string in the address bar to parameters in your method. | |
In both these examples the controller has been doing the "VC" portion of MVC — that is, the view and | |
controller work. The controller is returning HTML directly. Ordinarily you don't want controllers returning | |
HTML directly, since that becomes very cumbersome to code. Instead we'll typically use a separate view | |
template file to help generate the HTML response. Let's look next at how we can do this. | |
Adding a View | |
In this section you're going to modify the HelloWorldController class to use view template files to cleanly | |
encapsulate the process of generating HTML responses to a client. | |
You'll create a view template file using theRazor view engine introduced with ASP.NET MVC 3. Razor-based | |
view templates have a .cshtml file extension, and provide an elegant way to create HTML output using C#. Razor | |
minimizes the number of characters and keystrokes required when writing a view template, and enables a fast, | |
fluid coding workflow. | |
Start by creating a view template with the Index method in theHelloWorldController class. Currently the | |
Index method returns a string with a message that is hard-coded in the controller class. Change the Index | |
method to return a View object, as shown in the following code: | |
publicActionResultIndex() | |
{ | |
returnView(); | |
} | |
The Index method above uses a view template to generate an HTML response to the browser. Controller | |
methods (also known asaction methods), such as the Index method above, generally return anActionResult (or a | |
class derrived fromActionResult), not primitive types like string. | |
In the project, add a view template that you can use with the Index method. To do this, right-click inside the | |
Index method and clickAdd View. | |
The Add View dialog box appears. Leave the defaults the way they are and click the Add button: | |
The MvcMovie\Views\HelloWorld folder and the MvcMovie\Views\HelloWorld\Index.cshtml file are created. You | |
can see them in Solution Explorer: | |
The following shows the Index.cshtml file that was created: | |
Add the following HTML under the <h2> tag. | |
<p>Hello from our View Template!</p> | |
The complete MvcMovie\Views\HelloWorld\Index.cshtml file is shown below. | |
@{ | |
ViewBag.Title = "Index"; | |
} | |
<h2>Index</h2> | |
<p>Hello from our View Template!</p> | |
In solution explorer, right click the Index.cshtml file and selectView in Page Inspector. | |
ThePage Inspector tutorial has more information about this new tool. | |
Alternatively, run the application and browse to the HelloWorld controller (http://localhost:xxxx/HelloWorld). | |
The Index method in your controller didn't do much work; it simply ran the statement return View(), which | |
specified that the method should use a view template file to render a response to the browser. Because you | |
didn't explicitly specify the name of the view template file to use, ASP.NET MVC defaulted to using the | |
Index.cshtml view file in the \Views\HelloWorld folder. The image below shows the string hard-coded in the | |
view. | |
Looks pretty good. However, notice that the browser's title bar shows "Index My ASP.NET A" and the big link on | |
the top of the page says "your logo here." Below the "your logo here." link are registration and log in links, and | |
below that links to Home, About and Contact pages. Let's change some of these. | |
Changing Views and Layout Pages | |
First, you want to change the "your logo here." title at the top of the page. That text is common to every page. | |
It's actually implemented in only one place in the project, even though it appears on every page in the | |
application. Go to the /Views/Shared folder in Solution Explorer and open the _Layout.cshtml file. This file is | |
called a layout page and it's the shared "shell" that all other pages use. | |
Layout templates allow you to specify the HTML container layout of your site in one place and then apply it | |
across multiple pages in your site. Find the@RenderBody() line. RenderBody is a placeholder where all the | |
view-specific pages you create show up, "wrapped" in the layout page. For example, if you select the About link, | |
the Views\Home\About.cshtml view is rendered inside the RenderBody method. | |
Change the site-title heading in the layout template from "your logo here" to "MVC Movie". | |
<divclass="float-left"> | |
<pclass="site-title">@Html.ActionLink("MVC Movie", "Index", "Home")</p> | |
</div> | |
Replace the contents of the title element with the following markup: | |
<title>@ViewBag.Title - Movie App</title> | |
The ViewBag is a zzz (dict object) Run the application and notice that it now says "MVC Movie ". Click theAbout | |
link, and you see how that page shows "MVC Movie", too. We were able to make the change once in the layout | |
template and have all pages on the site reflect the new title. | |
The complete _Layout.cshtml file is shown below: | |
<!DOCTYPE html> | |
<htmllang="en"> | |
<head> | |
<metacharset="utf-8"/> | |
<title>@ViewBag.Title - Movie App</title> | |
<linkhref="~/favicon.ico"rel="shortcut icon"type="image/x-icon"/> | |
<linkhref="@System.Web.Optimization.BundleTable.Bundles.ResolveBundleUrl("~/Content/c | |
ss")"rel="stylesheet"type="text/css"/> | |
<linkhref="@System.Web.Optimization.BundleTable.Bundles.ResolveBundleUrl("~/Content/t | |
hemes/base/css")"rel="stylesheet"type="text/css"/> | |
<scriptsrc="@System.Web.Optimization.BundleTable.Bundles.ResolveBundleUrl("~/Scripts/ | |
js")"></script> | |
<metaname="viewport"content="width=device-width"/> | |
</head> | |
<body> | |
<header> | |
<divclass="content-wrapper"> | |
<divclass="float-left"> | |
<pclass="site-title">@Html.ActionLink("MVC Movie", "Index", "Home")</p> | |
</div> | |
<divclass="float-right"> | |
<sectionid="login"> | |
@Html.Partial("_LoginPartial") | |
</section> | |
<nav> | |
<ulid="menu"> | |
<li>@Html.ActionLink("Home", "Index", "Home")</li> | |
<li>@Html.ActionLink("About", "About", "Home")</li> | |
<li>@Html.ActionLink("Contact", "Contact", "Home")</li> | |
</ul> | |
</nav> | |
</div> | |
</div> | |
</header> | |
<divid="body"> | |
@RenderSection("featured", required: false) | |
<sectionclass="content-wrapper main-content clear-fix"> | |
@RenderBody() | |
</section> | |
</div> | |
<footer> | |
<divclass="content-wrapper"> | |
<divclass="float-left"> | |
<p>© @DateTime.Now.Year - My ASP.NET MVC Application</p> | |
</div> | |
<divclass="float-right"> | |
<ulid="social"> | |
<li><ahref="http://facebook.com"class="facebook">Facebook</a></li> | |
<li><ahref="http://twitter.com"class="twitter">Twitter</a></li> | |
</ul> | |
</div> | |
</div> | |
</footer> | |
</body> | |
</html> | |
Now, let's change the title of the Index view. | |
Open MvcMovie\Views\HelloWorld\Index.cshtml. There are two places to make a change: first, the text that | |
appears in the title of the browser, and then in the secondary header (the <h2> element). You'll make them | |
slightly different so you can see which bit of code changes which part of the app. | |
@{ | |
ViewBag.Title = "Movie List"; | |
} | |
<h2>My Movie List</h2> | |
<p>Hello from our View Template!</p> | |
To indicate the HTML title to display, the code above sets a Title property of the ViewBag object (which is in | |
the Index.cshtml view template). If you look back at the source code of the layout template, you’ll notice that | |
the template uses this value in the <title> element as part of the <head> section of the HTML that we | |
modified previously. Using this ViewBag approach, you can easily pass other parameters between your view | |
template and your layout file. | |
Run the application and browse to http://localhost:xx/HelloWorld. Notice that the browser title, the primary | |
heading, and the secondary headings have changed. (If you don't see changes in the browser, you might be | |
viewing cached content. Press Ctrl+F5 in your browser to force the response from the server to be loaded.) The | |
browser title is created with the ViewBag.Title we set in the Index.cshtml view template and the additional "- | |
Movie App" added in the layout file. | |
Also notice how the content in the Index.cshtml view template was merged with the _Layout.cshtml view | |
template and a single HTML response was sent to the browser. Layout templates make it really easy to make | |
changes that apply across all of the pages in your application. | |
Our little bit of "data" (in this case the "Hello from our View Template!" message) is hard-coded, though. The | |
MVC application has a "V" (view) and you've got a "C" (controller), but no "M" (model) yet. Shortly, we'll walk | |
through how create a database and retrieve model data from it. | |
Passing Data from the Controller to the View | |
Before we go to a database and talk about models, though, let's first talk about passing information from the | |
controller to a view. Controller classes are invoked in response to an incoming URL request. A controller class is | |
where you write the code that handles the incoming browser requests, retrieves data from a database, and | |
ultimately decides what type of response to send back to the browser. View templates can then be used from a | |
controller to generate and format an HTML response to the browser. | |
Controllers are responsible for providing whatever data or objects are required in order for a view template to | |
render a response to the browser. A best practice: A view template should never perform business logic or | |
interact with a database directly. Instead, a view template should work only with the data that's provided to it | |
by the controller. Maintaining this "separation of concerns" helps keep your code clean, testable and more | |
maintainable. | |
Currently, the Welcome action method in the HelloWorldController class takes a name and a numTimes | |
parameter and then outputs the values directly to the browser. Rather than have the controller render this | |
response as a string, let’s change the controller to use a view template instead. The view template will generate | |
a dynamic response, which means that you need to pass appropriate bits of data from the controller to the view | |
in order to generate the response. You can do this by having the controller put the dynamic data (parameters) | |
that the view template needs in a ViewBag object that the view template can then access. | |
Return to the HelloWorldController.cs file and change the Welcome method to add a Message and NumTimes | |
value to the ViewBag object. ViewBag is a dynamic object, which means you can put whatever you want in to | |
it; the ViewBag object has no defined properties until you put something inside it. TheASP.NET MVC model | |
binding system automatically maps the named parameters (nameand numTimes) from the query string in the | |
address bar to parameters in your method. The completeHelloWorldController.cs file looks like this: | |
usingSystem.Web; | |
usingSystem.Web.Mvc; | |
namespaceMvcMovie.Controllers | |
{ | |
publicclassHelloWorldController:Controller | |
{ | |
publicActionResultIndex() | |
{ | |
returnView(); | |
} | |
publicActionResultWelcome(string name,int numTimes =1) | |
{ | |
ViewBag.Message="Hello "+ name; | |
ViewBag.NumTimes= numTimes; | |
returnView(); | |
} | |
} | |
} | |
Now the ViewBag object contains data that will be passed to the view automatically. | |
Next, you need a Welcome view template! In the Build menu, select Build MvcMovie to make sure the project | |
is compiled. | |
Then right-click inside the Welcome method and click Add View. | |
Here's what the Add View dialog box looks like: | |
Click Add, and then add the following code under the < h2> element in the new Welcome.cshtml file. You'll | |
create a loop that says "Hello" as many times as the user says it should. The completeWelcome.cshtml file is | |
shown below. | |
@{ | |
ViewBag.Title = "Welcome"; | |
} | |
<h2>Welcome</h2> | |
<ul> | |
@for (int i=0; i < ViewBag.NumTimes; i++) { | |
<li>@ViewBag.Message</li> | |
} | |
</ul> | |
Run the application and browse to the following URL: | |
http://localhost:xx/HelloWorld/Welcome?name=Scott&numtimes=4 | |
Now data is taken from the URL and passed to the controller using themodel binder. The controller packages | |
the data into a ViewBag object and passes that object to the view. The view then displays the data as HTML to | |
the user. | |
Well, that was a kind of an "M" for model, but not the database kind. Let's take what we've learned and create a | |
database of movies. | |
Adding a Model | |
In this section you'll add some classes for managing movies in a database. These classes will be the "model" | |
part of the ASP.NET MVC application. | |
You’ll use a .NET Framework data-access technology known as the Entity Framework to define and work with | |
these model classes. The Entity Framework (often referred to as EF) supports a development paradigm called | |
Code First. Code First allows you to create model objects by writing simple classes. (These are also known as | |
POCO classes, from "plain-old CLR objects.") You can then have the database created on the fly from your | |
classes, which enables a very clean and rapid development workflow. | |
Adding Model Classes | |
In Solution Explorer, right click the Models folder, select Add, and then select New Item. | |
In the Add New Item dialog, select Class then name the class "Movie". | |
Add the following five properties to the Movie class: | |
publicclassMovie | |
{ | |
publicint ID {get;set;} | |
publicstringTitle{get;set;} | |
publicDateTimeReleaseDate{get;set;} | |
publicstringGenre{get;set;} | |
publicdecimalPrice{get;set;} | |
} | |
We'll use the Movie class to represent movies in a database. Each instance of a Movie object will correspond to | |
a row within a database table, and each property of the Movie class will map to a column in the table. | |
In the same file, add the following MovieDBContext class: | |
publicclassMovieDBContext:DbContext | |
{ | |
publicDbSet<Movie>Movies{get;set;} | |
} | |
The MovieDBContext class represents the Entity Framework movie database context, which handles fetching, | |
storing, and updating Movie class instances in a database. The MovieDBContext derives from theDbContext | |
base class provided by the Entity Framework. For more information about DbContext and DbSet, | |
seeProductivity Improvements for the Entity Framework. | |
In order to be able to reference DbContext and DbSet, you need to add the following using statement at the | |
top of the file: | |
usingSystem.Data.Entity; | |
The complete Movie.cs file is shown below. (Several using statements that are not needed have been removed.) | |
usingSystem; | |
usingSystem.Data.Entity; | |
namespaceMvcMovie.Models | |
{ | |
publicclassMovie | |
{ | |
publicint ID {get;set;} | |
publicstringTitle{get;set;} | |
publicDateTimeReleaseDate{get;set;} | |
publicstringGenre{get;set;} | |
publicdecimalPrice{get;set;} | |
} | |
publicclassMovieDBContext:DbContext | |
{ | |
publicDbSet<Movie>Movies{get;set;} | |
} | |
} | |
Creating a Connection String and Working with SQL Server LocalDB | |
The MovieDBContext class you created handles the task of connecting to the database and mapping Movie | |
objects to database records. One question you might ask, though, is how to specify which database it will | |
connect to. You'll do that by adding connection information in the Web.config file of the application. | |
Open the application root Web.config file. (Not the Web.configfile in the Views folder.) Open the Web.config file | |
outlined in red. | |
Add the following connection string to the <connectionStrings> element in the Web.config file. | |
<addname="MovieDBContext" | |
connectionString="Data | |
Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\Movies.mdf;Integrated | |
Security=True" | |
providerName="System.Data.SqlClient" | |
/> | |
The following example shows a portion of the Web.config file with the new connection string added: | |
<connectionStrings> | |
<addname="DefaultConnection" | |
connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=aspnet-MvcMovie- | |
2012213181139;Integrated Security=true" | |
providerName="System.Data.SqlClient" | |
/> | |
<addname="MovieDBContext" | |
connectionString="Data | |
Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\Movies.mdf;Integrated | |
Security=True" | |
providerName="System.Data.SqlClient" | |
/> | |
</connectionStrings> | |
This small amount of code and XML is everything you need to write in order to represent and store the movie | |
data in a database. | |
Next, you'll build a new MoviesController class that you can use to display the movie data and allow users | |
to create new movie listings. | |
Accessing Your Model's Data from a Controller | |
In this section, you'll create a new MoviesController class and write code that retrieves the movie data and | |
displays it in the browser using a view template. | |
Build the application before going on to the next step. | |
Right-click the Controllers folder and create a new MoviesController controller. The options below will not | |
appear until you build your application. Select the following options: | |
• Controller name: MoviesController. (This is the default. ) | |
• | |
Template: Controller with read/write actions and views, using Entity Framework. | |
• Model class: Movie (MvcMovie.Models). | |
• Data context class: MovieDBContext (MvcMovie.Models). | |
• Views: Razor (CSHTML). (The default.) | |
Click Add. Visual Studio Express creates the following files and folders: | |
• A MoviesController.csfile in the project's Controllers folder. | |
• A Movies folder in the project's Views folder. | |
• Create.cshtml, Delete.cshtml, Details.cshtml, Edit.cshtml, and Index.cshtml in the new Views\Movies folder. | |
ASP.NET MVC 4 automatically created the CRUD (create, read, update, and delete) action methods and views | |
for you (the automatic creation of CRUD action methods and views is known as scaffolding). You now have a | |
fully functional web application that lets you create, list, edit, and delete movie entries. | |
Run the application and browse to the Movies controller by appending /Movies to the URL in the address bar | |
of your browser. Because the application is relying on the default routing (defined in the Global.asax file), the | |
browser request http://localhost:xxxxx/Movies is routed to the default Index action method of the Movies | |
controller. In other words, the browser request http://localhost:xxxxx/Movies is effectively the same as the | |
browser request http://localhost:xxxxx/Movies/Index. The result is an empty list of movies, because you haven't | |
added any yet. | |
Creating a Movie | |
Select the Create New link. Enter some details about a movie and then click the Create button. | |
Clicking the Create button causes the form to be posted to the server, where the movie information is saved in | |
the database. You're then redirected to the /Movies URL, where you can see the newly created movie in the | |
listing. | |
Create a couple more movie entries. Try the Edit, Details, and Delete links, which are all functional. | |
Examining the Generated Code | |
Open the Controllers\MoviesController.cs file and examine the generated Index method. A portion of the movie | |
controller with theIndex method is shown below. | |
publicclassMoviesController:Controller | |
{ | |
privateMovieDBContext db =newMovieDBContext(); | |
// | |
// GET: /Movies/ | |
publicActionResultIndex() | |
{ | |
returnView(db.Movies.ToList()); | |
} | |
The following line from the MoviesController class instantiates a movie database context, as described | |
previously. You can use the movie database context to query, edit, and delete movies. | |
privateMovieDBContext db =newMovieDBContext(); | |
A request to the Movies controller returns all the entries in the Movies table of the movie database and then | |
passes the results to the Index view. | |
Strongly Typed Models and the @model Keyword | |
Earlier in this tutorial, you saw how a controller can pass data or objects to a view template using the ViewBag | |
object. The ViewBag is a dynamic object that provides a convenient late-bound way to pass information to a | |
view. | |
ASP.NET MVC also provides the ability to pass strongly typed data or objects to a view template. This strongly | |
typed approach enables better compile-time checking of your code and richer IntelliSense in the Visual Studio | |
Express editor. The scaffolding mechanism in Visual Studio Express used this approach with the | |
MoviesController class and view templates when it created the methods and views. | |
In the Controllers\MoviesController.cs file examine the generated Details method. A portion of the movie | |
controller with theDetails method is shown below. | |
publicActionResultDetails(int id =0) | |
{ | |
Movie movie =db.Movies.Find(id); | |
if(movie ==null) | |
{ | |
returnHttpNotFound(); | |
} | |
returnView(movie); | |
} | |
An instance of the Movie model is passed to the Details view. | |
By including a @model statement at the top of the view template file, you can specify the type of object that the | |
view expects. When you created the movie controller, Visual Studio Express automatically included the | |
following@model statement at the top of the Details.cshtml file: | |
@model MvcMovie.Models.Movie | |
This @model directive allows you to access the movie that the controller passed to the view by using a Model | |
object that's strongly typed. For example, in the Details.cshtml template, the code passes each movie field to | |
the DisplayNameFor and DisplayFor HTML Helpers with the strongly typed Model object. The Create and Edit | |
methods and view templates also pass a movie model object. | |
Examine the Index.cshtml view template and the Index method in the MoviesController.cs file. Notice how the | |
code creates aList object when it calls the View helper method in the Index action method. The code then | |
passes this Movies list from the controller to the view: | |
publicActionResultIndex() | |
{ | |
returnView(db.Movies.ToList()); | |
} | |
When you created the movie controller, Visual Studio Express automatically included the following@model | |
statement at the top of the Index.cshtml file: | |
@model IEnumerable<MvcMovie.Models.Movie> | |
This @model directive allows you to access the list of movies that the controller passed to the view by using a | |
Model object that's strongly typed. For example, in the Index.cshtml template, the code loops through the | |
movies by doing a foreach statement over the strongly typed Model object: | |
@foreach (var item in Model) { | |
<tr> | |
<td> | |
@Html.DisplayFor(modelItem => item.Title) | |
</td> | |
<td> | |
@Html.DisplayFor(modelItem => item.ReleaseDate) | |
</td> | |
<td> | |
@Html.DisplayFor(modelItem => item.Genre) | |
</td> | |
<td> | |
@Html.DisplayFor(modelItem => item.Price) | |
</td> | |
<th> | |
@Html.DisplayFor(modelItem => item.Rating) | |
</th> | |
<td> | |
@Html.ActionLink("Edit", "Edit", new { id=item.ID }) | | |
@Html.ActionLink("Details", "Details", { id=item.ID }) | | |
@Html.ActionLink("Delete", "Delete", { id=item.ID }) | |
</td> | |
</tr> | |
} | |
Because the Model object is strongly typed (as an IEnumerable<Movie> object), each item object in the loop | |
is typed as Movie. Among other benefits, this means that you get compile-time checking of the code and full | |
IntelliSense support in the code editor: | |
Working with SQL Server LocalDB | |
Entity Framework Code First detected that the database connection string that was provided pointed to a | |
Movies database that didn’t exist yet, so Code First created the database automatically. You can verify that it's | |
been created by looking in the App_Data folder. If you don't see the Movies.sdf file, click the Show All Files | |
button in theSolution Explorer toolbar, click the Refresh button, and then expand the App_Data folder. | |
Double-click Movies.mdf to open DATABASE EXPLORER. Then expand the Tables folder to see the tables that | |
have been created in the database. | |
There are two tables, one for the Movie entity set and theEdmMetadata table. The EdmMetadata table is used | |
by the Entity Framework to determine when the model and the database are out of sync. | |
Right-click the Movies table and select Show Table Data to see the data you created. | |
Right-click the Movies table and select Open Table Definition to see the table structure that Entity Framework | |
Code First created for you. | |
Notice how the schema of the Movies table maps to the Movie class you created earlier. Entity Framework | |
Code First automatically created this schema for you based on your Movie class. | |
When you're finished, close the connection by right clicking Movies.mdf and selecting Close Connection. (If you | |
don't close the connection, you might get an error the next time you run the project). | |
You now have the database and a simple listing page to display content from it. In the next tutorial, we'll | |
examine the rest of the scaffolded code and add a SearchIndex method and a SearchIndex view that lets | |
you search for movies in this database. | |
Examining the Edit Methods and Edit View | |
In this section, you'll examine the generated action methods and views for the movie controller. Then you'll add | |
a custom search page. | |
Run the application and browse to the Movies controller by appending /Movies to the URL in the address bar | |
of your browser. Hold the mouse pointer over an Edit link to see the URL that it links to. | |
The Edit link was generated by the Html.ActionLink method in the Views\Movies\Index.cshtml view: | |
@Html.ActionLink("Edit", "Edit", new { id=item.ID }) | |
The Html object is a helper that's exposed using a property on the System.Web.Mvc.WebViewPage base class. | |
The ActionLinkmethod of the helper makes it easy to dynamically generate HTML hyperlinks that link to | |
action methods on controllers. The first argument to the ActionLink method is the link text to render (for | |
example,<a>Edit Me</a>). The second argument is the name of the action method to invoke. The final | |
argument is ananonymous object that generates the route data (in this case, the ID of 4). | |
The generated link shown in the previous image is http://localhost:xxxxx/Movies/Edit/4. The default route | |
(established in Global.asax.cs) takes the URL pattern {controller}/{action}/{id}. Therefore, ASP.NET | |
translateshttp://localhost:xxxxx/Movies/Edit/4 into a request to the Edit action method of the Movies | |
controller with the parameter ID equal to 4. | |
You can also pass action method parameters using a query string. For example, the URL | |
http://localhost:xxxxx/Movies/Edit?ID=4 also passes the parameter ID of 4 to the Edit action method of | |
theMovies controller. | |
Open the Movies controller. The two Edit action methods are shown below. | |
// | |
// GET: /Movies/Edit/5 | |
publicActionResultEdit(int id =0) | |
{ | |
Movie movie =db.Movies.Find(id); | |
if(movie ==null) | |
{ | |
returnHttpNotFound(); | |
} | |
returnView(movie); | |
} | |
// | |
// POST: /Movies/Edit/5 | |
[HttpPost] | |
publicActionResultEdit(Movie movie) | |
{ | |
if(ModelState.IsValid) | |
{ | |
db.Entry(movie).State=EntityState.Modified; | |
db.SaveChanges(); | |
returnRedirectToAction("Index"); | |
} | |
returnView(movie); | |
} | |
Notice the second Edit action method is preceded by the HttpPost attribute. This attribute specifies that that | |
overload of the Edit method can be invoked only for POST requests. You could apply the HttpGet attribute to | |
the first edit method, but that's not necessary because it's the default. (We'll refer to action methods that are | |
implicitly assigned the HttpGet attribute as HttpGet methods.) | |
The HttpGetEdit method takes the movie ID parameter, looks up the movie using the Entity Framework Find | |
method, and returns the selected movie to the Edit view. The ID parameter specifies a default value of zero if | |
the Edit method is called without a parameter. If a movie cannot be found, HttpNotFound is returned. When | |
the scaffolding system created the Edit view, it examined the Movie class and created code to render <label> | |
and <input> elements for each property of the class. The following example shows the Edit view that was | |
generated: | |
@model MvcMovie.Models.Movie | |
@{ | |
ViewBag.Title = "Edit"; | |
} | |
<h2>Edit</h2> | |
<scriptsrc="@Url.Content("~/Scripts/jquery.validate.min.js")"type="text/javascript">< | |
/script> | |
<scriptsrc="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")"type="text/j | |
avascript"></script> | |
@using (Html.BeginForm()) { | |
@Html.ValidationSummary(true) | |
<fieldset> | |
<legend>Movie</legend> | |
@Html.HiddenFor(model => model.ID) | |
<divclass="editor-label"> | |
@Html.LabelFor(model => model.Title) | |
</div> | |
<divclass="editor-field"> | |
@Html.EditorFor(model => model.Title) | |
@Html.ValidationMessageFor(model => model.Title) | |
</div> | |
<divclass="editor-label"> | |
@Html.LabelFor(model => model.ReleaseDate) | |
</div> | |
<divclass="editor-field"> | |
@Html.EditorFor(model => model.ReleaseDate) | |
@Html.ValidationMessageFor(model => model.ReleaseDate) | |
</div> | |
<divclass="editor-label"> | |
@Html.LabelFor(model => model.Genre) | |
</div> | |
<divclass="editor-field"> | |
@Html.EditorFor(model => model.Genre) | |
@Html.ValidationMessageFor(model => model.Genre) | |
</div> | |
<divclass="editor-label"> | |
@Html.LabelFor(model => model.Price) | |
</div> | |
<divclass="editor-field"> | |
@Html.EditorFor(model => model.Price) | |
@Html.ValidationMessageFor(model => model.Price) | |
</div> | |
<p> | |
<inputtype="submit"value="Save"/> | |
</p> | |
</fieldset> | |
} | |
<div> | |
@Html.ActionLink("Back to List", "Index") | |
</div> | |
Notice how the view template has a @model MvcMovie.Models.Movie statement at the top of the file — this | |
specifies that the view expects the model for the view template to be of type Movie. | |
The scaffolded code uses several helper methods to streamline the HTML markup. TheHtml.LabelFor helper | |
displays the name of the field ("Title", "ReleaseDate", "Genre", or "Price"). TheHtml.EditorFor helper renders | |
an HTML <input> element. TheHtml.ValidationMessageFor helper displays any validation messages | |
associated with that property. | |
Run the application and navigate to the /Movies URL. Click anEdit link. In the browser, view the source for the | |
page. The HTML for the form element is shown below. | |
<formaction="/Movies/Edit/4"method="post"><fieldset> | |
<legend>Movie</legend> | |
<inputdata-val="true"data-val-number="The field ID must be a number."data-val- | |
required="The ID field is required."id="ID"name="ID"type="hidden"value="4"/> | |
<divclass="editor-label"> | |
<labelfor="Title">Title</label> | |
</div> | |
<divclass="editor-field"> | |
<inputclass="text-box single-line"id="Title"name="Title"type="text"value="Rio | |
Bravo"/> | |
<spanclass="field-validation-valid"data-valmsg-for="Title"data-valmsg- | |
replace="true"></span> | |
</div> | |
<divclass="editor-label"> | |
<labelfor="ReleaseDate">ReleaseDate</label> | |
</div> | |
<divclass="editor-field"> | |
<inputclass="text-box single-line"data-val="true"data-val-date="The field ReleaseDate | |
must be a date."data-val-required="The ReleaseDate field is | |
required."id="ReleaseDate"name="ReleaseDate"type="text"value="4/15/1959 12:00:00 | |
AM"/> | |
<spanclass="field-validation-valid"data-valmsg-for="ReleaseDate"data-valmsg- | |
replace="true"></span> | |
</div> | |
<divclass="editor-label"> | |
<labelfor="Genre">Genre</label> | |
</div> | |
<divclass="editor-field"> | |
<inputclass="text-box single-line"id="Genre"name="Genre"type="text"value="Western"/> | |
<spanclass="field-validation-valid"data-valmsg-for="Genre"data-valmsg- | |
replace="true"></span> | |
</div> | |
<divclass="editor-label"> | |
<labelfor="Price">Price</label> | |
</div> | |
<divclass="editor-field"> | |
<inputclass="text-box single-line"data-val="true"data-val-number="The field Price | |
must be a number."data-val-required="The Price field is | |
required."id="Price"name="Price"type="text"value="2.99"/> | |
<spanclass="field-validation-valid"data-valmsg-for="Price"data-valmsg- | |
replace="true"></span> | |
</div> | |
<p> | |
<inputtype="submit"value="Save"/> | |
</p> | |
</fieldset> | |
</form> | |
The <input> elements are in an HTML <form> element whose action attribute is set to post to the | |
/Movies/Edit URL. The form data will be posted to the server when the Edit button is clicked. | |
Processing the POST Request | |
The following listing shows the HttpPost version of the Edit action method. | |
[HttpPost] | |
publicActionResultEdit(Movie movie) | |
{ | |
if(ModelState.IsValid) | |
{ | |
db.Entry(movie).State=EntityState.Modified; | |
db.SaveChanges(); | |
returnRedirectToAction("Index"); | |
} | |
returnView(movie); | |
} | |
The ASP.NET MVC model binder takes the posted form values and creates aMovie object that's passed as the | |
movie parameter. TheModelState.IsValid method verifies that the data submitted in the form can be used | |
to modify (edit or update) a Movie object. If the data is valid, the movie data is saved to the Movies collection | |
of the db (MovieDBContext instance). The new movie data is saved to the database by calling the | |
SaveChanges method ofMovieDBContext. After saving the data, the code redirects the user to the Index | |
action method of the MoviesController class, which displays the of movie collection, including the changes | |
just made.. | |
If the posted values aren't valid, they are redisplayed in the form. TheHtml.ValidationMessageFor helpers | |
in the Edit.cshtml view template take care of displaying appropriate error messages. | |
Note about locales If you normally work with a locale other than English, see Supporting ASP.NET MVC | |
Validation with Non-English Locales. The decimal field may require a common, not a decimal point. As a | |
temporary fix, you can add the globalization element to the projects root web.config file. The following code | |
shows the globalization element with the culture set to United States English. | |
<system.web> | |
<globalizationculture="en-US"/> | |
<!--elements removed for clarity--> | |
</system.web> | |
All the HttpGet methods follow a similar pattern. They get a movie object (or list of objects, in the case of | |
Index), and pass the model to the view. The Create method passes an empty movie object to the Create view. | |
All the methods that create, edit, delete, or otherwise modify data do so in the HttpPost overload of the | |
method. Modifying data in an HTTP GET method is a security risk, as described in the blog post entryASP.NET | |
MVC Tip #46 – Don’t use Delete Links because they create Security Holes. Modifying data in a GET method also | |
violates HTTP best practices and the architectural REST pattern, which specifies that GET requests should not | |
change the state of your application. In other words, performing a GET operation should be a safe operation | |
that has no side effects and doesn't modify your persisted data. | |
Adding a Search Method and Search View | |
In this section you'll add a SearchIndex action method that lets you search movies by genre or name. This will | |
be available using the /Movies/SearchIndex URL. The request will display an HTML form that contains input | |
elements that a user can enter in order to search for a movie. When a user submits the form, the action method | |
will get the search values posted by the user and use the values to search the database. | |
Displaying the SearchIndex Form | |
Start by adding a SearchIndex action method to the existingMoviesController class. The method will | |
return a view that contains an HTML form. Here's the code: | |
publicActionResultSearchIndex(string searchString) | |
{ | |
var movies =from m in db.Movies | |
select m; | |
if(!String.IsNullOrEmpty(searchString)) | |
{ | |
movies= movies.Where(s => s.Title.Contains(searchString)); | |
} | |
returnView(movies); | |
} | |
The first line of the SearchIndex method creates the followingLINQ query to select the movies: | |
var movies =from m in db.Movies | |
select m; | |
The query is defined at this point, but hasn't yet been run against the data store. | |
If the searchString parameter contains a string, the movies query is modified to filter on the value of the | |
search string, using the following code: | |
if(!String.IsNullOrEmpty(searchString)) | |
{ | |
movies= movies.Where(s => s.Title.Contains(searchString)); | |
} | |
The s => s.Title code above is aLambda Expression. Lambdas are used in method-basedLINQ queries as | |
arguments to standard query operator methods such asWhere method used in the above code. LINQ queries | |
are not executed when they are defined or when they are modified by calling a method such as Where or | |
OrderBy. Instead, query execution is deferred, which means that the evaluation of an expression is delayed | |
until its realized value is actually iterated over or theToList method is called. In the SearchIndex sample, the | |
query is executed in the SearchIndex view. For more information about deferred query execution, see Query | |
Execution. | |
Now you can implement the SearchIndex view that will display the form to the user. Right-click inside the | |
SearchIndex method and then click Add View. In the Add View dialog box, specify that you're going to pass | |
a Movie object to the view template as its model class. In the Scaffold template list, choose List, then click | |
Add. | |
When you click the Add button, the Views\Movies\SearchIndex.cshtml view template is created. Because you | |
selected List in the Scaffold template list, Visual Studio Express automatically generated (scaffolded) some | |
default markup in the view. The scaffolding created an HTML form. It examined the Movie class and created | |
code to render <label> elements for each property of the class. The listing below shows the Create view that | |
was generated: | |
@model IEnumerable<MvcMovie.Models.Movie> | |
@{ | |
ViewBag.Title = "SearchIndex"; | |
} | |
<h2>SearchIndex</h2> | |
<p> | |
@Html.ActionLink("Create New", "Create") | |
</p> | |
<table> | |
<tr> | |
<th> | |
Title | |
</th> | |
<th> | |
ReleaseDate | |
</th> | |
<th> | |
Genre | |
</th> | |
<th> | |
Price | |
</th> | |
<th></th> | |
</tr> | |
@foreach (var item in Model) { | |
<tr> | |
<td> | |
@Html.DisplayFor(modelItem => item.Title) | |
</td> | |
<td> | |
@Html.DisplayFor(modelItem => item.ReleaseDate) | |
</td> | |
<td> | |
@Html.DisplayFor(modelItem => item.Genre) | |
</td> | |
<td> | |
@Html.DisplayFor(modelItem => item.Price) | |
</td> | |
<td> | |
@Html.ActionLink("Edit", "Edit", new { id=item.ID }) | | |
@Html.ActionLink("Details", "Details", new { id=item.ID }) | | |
@Html.ActionLink("Delete", "Delete", new { id=item.ID }) | |
</td> | |
</tr> | |
} | |
</table> | |
Run the application and navigate to /Movies/SearchIndex. Append a query string such as | |
?searchString=ghost to the URL. The filtered movies are displayed. | |
If you change the signature of the SearchIndex method to have a parameter named id, the id parameter will | |
match the{id} placeholder for the default routes set in the Global.asax file. | |
{controller}/{action}/{id} | |
The original SearchIndex method looks like this:: | |
publicActionResultSearchIndex(string searchString) | |
{ | |
var movies =from m in db.Movies | |
select m; | |
if(!String.IsNullOrEmpty(searchString)) | |
{ | |
movies= movies.Where(s => s.Title.Contains(searchString)); | |
} | |
returnView(movies); | |
} | |
The modified SearchIndex method would look as follows: | |
publicActionResultSearchIndex(string id) | |
{ | |
string searchString = id; | |
var movies =from m in db.Movies | |
select m; | |
if(!String.IsNullOrEmpty(searchString)) | |
{ | |
movies= movies.Where(s => s.Title.Contains(searchString)); | |
} | |
returnView(movies); | |
} | |
You can now pass the search title as route data (a URL segment) instead of as a query string value. | |
However, you can't expect users to modify the URL every time they want to search for a movie. So now you | |
you'll add UI to help them filter movies. If you changed the signature of the SearchIndex method to test how | |
to pass the route-bound ID parameter, change it back so that your SearchIndex method takes a string | |
parameter named searchString: | |
publicActionResultSearchIndex(string searchString) | |
{ | |
var movies =from m in db.Movies | |
select m; | |
if(!String.IsNullOrEmpty(searchString)) | |
{ | |
movies= movies.Where(s => s.Title.Contains(searchString)); | |
} | |
returnView(movies); | |
} | |
Open the Views\Movies\SearchIndex.cshtml file, and just after @Html.ActionLink("Create New", | |
"Create"), add the following: | |
@using (Html.BeginForm()){ | |
<p> Title: @Html.TextBox("SearchString")<br/> | |
<inputtype="submit"value="Filter"/></p> | |
} | |
The following example shows a portion of the Views\Movies\SearchIndex.cshtml file with the added filtering | |
markup. | |
@model IEnumerable<MvcMovie.Models.Movie> | |
@{ | |
ViewBag.Title = "SearchIndex"; | |
} | |
<h2>SearchIndex</h2> | |
<p> | |
@Html.ActionLink("Create New", "Create") | |
@using (Html.BeginForm()){ | |
<p> Title: @Html.TextBox("SearchString") <br/> | |
<inputtype="submit"value="Filter"/></p> | |
} | |
</p> | |
The Html.BeginForm helper creates an opening <form> tag. The Html.BeginForm helper causes the form to | |
post to itself when the user submits the form by clicking the Filter button. | |
Run the application and try searching for a movie. | |
There's no HttpPost overload of the SearchIndex method. You don't need it, because the method isn't | |
changing the state of the application, just filtering data. | |
You could add the following HttpPost SearchIndex method. In that case, the action invoker would match | |
the HttpPost SearchIndex method, and the HttpPost SearchIndex method would run as shown in the | |
image below. | |
[HttpPost] | |
publicstringSearchIndex(FormCollection fc,string searchString) | |
{ | |
return"<h3> From [HttpPost]SearchIndex: "+ searchString +"</h3>"; | |
} | |
However, even if you add this HttpPost version of the SearchIndex method, there's a limitation in how this | |
has all been implemented. Imagine that you want to bookmark a particular search or you want to send a link to | |
friends that they can click in order to see the same filtered list of movies. Notice that the URL for the HTTP | |
POST request is the same as the URL for the GET request (localhost:xxxxx/Movies/SearchIndex) -- there's no | |
search information in the URL itself. Right now, the search string information is sent to the server as a form field | |
value. This means you can't capture that search information to bookmark or send to friends in a URL. | |
The solution is to use an overload of BeginForm that specifies that the POST request should add the search | |
information to the URL and that is should be routed to the HttpGet version of the SearchIndex method. | |
Replace the existing parameterless BeginForm method with the following: | |
@using (Html.BeginForm("SearchIndex","Movies",FormMethod.Get)) | |
Now when you submit a search, the URL contains a search query string. Searching will also go to the HttpGet | |
SearchIndex action method, even if you have a HttpPost SearchIndex method. | |
Adding Search by Genre | |
If you added the HttpPost version of the SearchIndex method, delete it now. | |
Next, you'll add a feature to let users search for movies by genre. Replace the SearchIndex method with the | |
following code: | |
publicActionResultSearchIndex(string movieGenre,string searchString) | |
{ | |
varGenreLst=newList<string>(); | |
varGenreQry=from d in db.Movies | |
orderby d.Genre | |
select d.Genre; | |
GenreLst.AddRange(GenreQry.Distinct()); | |
ViewBag.movieGenre =newSelectList(GenreLst); | |
var movies =from m in db.Movies | |
select m; | |
if(!String.IsNullOrEmpty(searchString)) | |
{ | |
movies= movies.Where(s => s.Title.Contains(searchString)); | |
} | |
if(string.IsNullOrEmpty(movieGenre)) | |
returnView(movies); | |
else | |
{ | |
returnView(movies.Where(x => x.Genre== movieGenre)); | |
} | |
} | |
This version of the SearchIndex method takes an additional parameter, namely movieGenre. The first few | |
lines of code create aList object to hold movie genres from the database. | |
The following code is a LINQ query that retrieves all the genres from the database. | |
varGenreQry=from d in db.Movies | |
orderby d.Genre | |
select d.Genre; | |
The code uses the AddRange method of the generic List collection to add all the distinct genres to the list. | |
(Without the Distinct modifier, duplicate genres would be added — for example, comedy would be added | |
twice in our sample). The code then stores the list of genres in the ViewBag object. | |
The following code shows how to check the movieGenre parameter. If it's not empty, the code further | |
constrains the movies query to limit the selected movies to the specified genre. | |
if(string.IsNullOrEmpty(movieGenre)) | |
returnView(movies); | |
else | |
{ | |
returnView(movies.Where(x => x.Genre== movieGenre)); | |
} | |
Adding Markup to the SearchIndex View to Support Search by Genre | |
Add an Html.DropDownList helper to the Views\Movies\SearchIndex.cshtml file, just before the TextBox | |
helper. The completed markup is shown below: | |
<p> | |
@Html.ActionLink("Create New", "Create") | |
@using (Html.BeginForm("SearchIndex","Movies",FormMethod.Get)){ | |
<p>Genre: @Html.DropDownList("movieGenre", "All") | |
Title: @Html.TextBox("SearchString") | |
<inputtype="submit"value="Filter"/></p> | |
} | |
</p> | |
Run the application and browse to /Movies/SearchIndex. Try a search by genre, by movie name, and by both | |
criteria. | |
In this section you examined the CRUD action methods and views generated by the framework. You created a | |
search action method and view that let users search by movie title and genre. In the next section, you'll look at | |
how to add a property to the Movie model and how to add an initializer that will automatically create a test | |
database. | |
Adding a New Field to the Movie Model and | |
Table | |
In this section you'll make some changes to the model classes and learn how you can update the database | |
schema to match the model changes. | |
Adding a Rating Property to the Movie Model | |
Start by adding a new Rating property to the existing Movie class. Open the Models\Movie.cs file and add the | |
Rating property like this one: | |
publicstringRating{get;set;} | |
The complete Movie class now looks like the following code: | |
publicclassMovie | |
{ | |
publicint ID {get;set;} | |
publicstringTitle{get;set;} | |
publicDateTimeReleaseDate{get;set;} | |
publicstringGenre{get;set;} | |
publicdecimalPrice{get;set;} | |
publicstringRating{get;set;} | |
} | |
Recompile the application using the Build > Build Movie menu command. | |
Now that you've updated the Model class, you also need to update the \Views\Movies\Index.cshtml and | |
\Views\Movies\Create.cshtml view templates in order to display the new Rating property in the browser view. | |
Open the \Views\Movies\Index.cshtml file and add a <th>Rating</th> column heading just after the Price | |
column. Then add a <td> column near the end of the template to render the @item.Rating value. Below is | |
what the updated Index.cshtml view template looks like: | |
@model IEnumerable<MvcMovie.Models.Movie> | |
@{ | |
ViewBag.Title = "Index"; | |
} | |
<h2>Index</h2> | |
<p> | |
@Html.ActionLink("Create New", "Create") | |
</p> | |
<table> | |
<tr> | |
<th> | |
@Html.DisplayNameFor(model => model.Title) | |
</th> | |
<th> | |
@Html.DisplayNameFor(model => model.ReleaseDate) | |
</th> | |
<th> | |
@Html.DisplayNameFor(model => model.Genre) | |
</th> | |
<th> | |
@Html.DisplayNameFor(model => model.Price) | |
</th> | |
<th> | |
@Html.DisplayNameFor(model => model.Rating) | |
</th> | |
<th></th> | |
</tr> | |
@foreach (var item in Model) { | |
<tr> | |
<td> | |
@Html.DisplayFor(modelItem => item.Title) | |
</td> | |
<td> | |
@Html.DisplayFor(modelItem => item.ReleaseDate) | |
</td> | |
<td> | |
@Html.DisplayFor(modelItem => item.Genre) | |
</td> | |
<td> | |
@Html.DisplayFor(modelItem => item.Price) | |
</td> | |
<td> | |
@Html.DisplayFor(modelItem => item.Rating) | |
</td> | |
<td> | |
@Html.ActionLink("Edit", "Edit", new { id=item.ID }) | | |
@Html.ActionLink("Details", "Details", new { id=item.ID }) | | |
@Html.ActionLink("Delete", "Delete", new { id=item.ID }) | |
</td> | |
</tr> | |
} | |
</table> | |
Next, open the \Views\Movies\Create.cshtml file and add the following markup near the end of the form. This | |
renders a text box so that you can specify a rating when a new movie is created. | |
<divclass="editor-label"> | |
@Html.LabelFor(model => model.Rating) | |
</div> | |
<divclass="editor-field"> | |
@Html.EditorFor(model => model.Rating) | |
@Html.ValidationMessageFor(model => model.Rating) | |
</div> | |
Managing Model and Database Schema Differences | |
You've now updated the application code to support the new Rating property. | |
Now run the application and navigate to the /Movies URL. When you do this, though, you'll see one of the | |
following errors: | |
You're seeing this error because the updated Movie model class in the application is now different than the | |
schema of the Movie table of the existing database. (There's no Rating column in the database table.) | |
By default, when you use Entity Framework Code First to automatically create a database, as you did earlier in | |
this tutorial, Code First adds a table to the database to help track whether the schema of the database is in sync | |
with the model classes it was generated from. If they aren't in sync, the Entity Framework throws an error. This | |
makes it easier to track down issues at development time that you might otherwise only find (by obscure | |
errors) at run time. The sync-checking feature is what causes the error message to be displayed that you just | |
saw. | |
There are two approaches to resolving the error: | |
1. Have the Entity Framework automatically drop and re-create the database based on the new model class | |
schema. This approach is very convenient when doing active development on a test database; it allows | |
you to quickly evolve the model and database schema together. The downside, though, is that you lose | |
existing data in the database — so you don't want to use this approach on a production database! | |
2. Explicitly modify the schema of the existing database so that it matches the model classes. The advantage | |
of this approach is that you keep your data. You can make this change either manually or by creating a | |
database change script. | |
For this tutorial, we'll use the first approach — you'll have the Entity Framework Code First automatically re- | |
create the database anytime the model changes. | |
Automatically Re-Creating the Database on Model Changes | |
Let's update the application so that Code First automatically drops and re-creates the database anytime you | |
change the model for the application. | |
Warning You should enable this approach of automatically dropping and re-creating the database only when | |
you're using a development or test database, and never on a production database that contains real data. Using | |
it on a production server can lead to data loss. | |
Stop the debugger. In Solution Explorer, right click the Models folder, select Add, and then select New Item. | |
In the Add New Item dialog, select Class then name the class "MovieInitializer". Update the | |
MovieInitializer class to contain the following code: | |
usingSystem; | |
usingSystem.Collections.Generic; | |
usingSystem.Data.Entity; | |
namespaceMvcMovie.Models{ | |
publicclassMovieInitializer:DropCreateDatabaseIfModelChanges<MovieDBContext>{ | |
protectedoverridevoidSeed(MovieDBContext context){ | |
var movies =newList<Movie>{ | |
newMovie{Title="When Harry Met Sally", | |
ReleaseDate=DateTime.Parse("1989-1-11"), | |
Genre="Romantic Comedy", | |
Rating="R", | |
Price=7.99M}, | |
newMovie{Title="Ghostbusters ", | |
ReleaseDate=DateTime.Parse("1984-3-13"), | |
Genre="Comedy", | |
Rating="R", | |
Price=8.99M}, | |
newMovie{Title="Ghostbusters 2", | |
ReleaseDate=DateTime.Parse("1986-2-23"), | |
Genre="Comedy", | |
Rating="R", | |
Price=9.99M}, | |
newMovie{Title="Rio Bravo", | |
ReleaseDate=DateTime.Parse("1959-4-15"), | |
Genre="Western", | |
Rating="R", | |
Price=3.99M}, | |
}; | |
movies.ForEach(d => context.Movies.Add(d)); | |
} | |
} | |
} | |
The MovieInitializer class specifies that the database used by the model should be dropped and | |
automatically re-created if the model classes ever change.DropCreateDatabaseIfModelChanges initializer | |
specifies the DB should be re-created only if the schema changes. Alternatively, you could use | |
theDropCreateDatabaseAlways initializer to always recreate and re-seed the database with data the first time | |
that a context is used in the application domain. TheDropCreateDatabaseAlways approach is useful in some | |
integration testing scenarios. The code that you inserted into the MovieInitializer class includes a includes a | |
Seed method that specifies some default data to automatically add to the database any time it's created (or re- | |
created). This provides a useful way to populate the database with some test data, without requiring you to | |
manually populate it each time you make a model change. | |
Now that you've defined the MovieInitializer class, you'll want to wire it up so that each time the | |
application runs, it checks whether the model classes are different from the schema in the database. If they are, | |
you can run the initializer to re-create the database to match the model and then populate the database with | |
the sample data. | |
Open the Global.asax filet: | |
The Global.asax file contains the class that defines the entire application for the project, and contains an | |
Application_Start event handler that runs when the application first starts. | |
At the beginning of the Application_Start method, add a call to Database.SetInitializer as shown | |
below: | |
protectedvoidApplication_Start() | |
{ | |
Database.SetInitializer<MovieDBContext>(newMovieInitializer()); | |
AreaRegistration.RegisterAllAreas(); | |
// Use LocalDB for Entity Framework by default | |
Database.DefaultConnectionFactory=newSqlConnectionFactory("Data | |
Source=(localdb)\v11.0; Integrated Security=True; MultipleActiveResultSets=True"); | |
RegisterGlobalFilters(GlobalFilters.Filters); | |
RegisterRoutes(RouteTable.Routes); | |
BundleTable.Bundles.RegisterTemplateBundles(); | |
} | |
Put the cursor on the red squiggly line (on MovieDBContext, orMovieInitializer ) right click and select | |
Resolve, then using MvcMovie.Models; | |
Alternatively, add the using statement to the top of the file. The using statement references the namespace | |
where our MovieInitializer class lives: | |
usingMvcMovie.Models;// MovieInitializer | |
The Database.SetInitializer statement you just added indicates that the database used by the | |
MovieDBContext instance should be automatically deleted and re-created if the schema and the database | |
don't match. And as you saw, it will also populate the database with the sample data that's specified in the | |
MovieInitializer class. | |
Close the Global.asax file. | |
Re-run the application and navigate to the /Movies URL. When the application starts, it detects that the model | |
structure no longer matches the database schema. It automatically re-creates the database to match the new | |
model structure and populates the database with the sample movies: | |
<=""> | |
Click the Create New link to add a new movie. Note that you can add a rating. | |
Click Create. The new movie, including the rating, now shows up in the movies listing: | |
You should also add the Rating field to the Edit view template. | |
In this section you saw how you can modify model objects and keep the database in sync with the changes. You | |
also learned a way to populate a newly created database with sample data so you can try out scenarios. Next, | |
let's look at how you can add richer validation logic to the model classes and enable some business rules to be | |
enforced. | |
Adding Validation to the Model | |
In this this section you'll add validation logic to the Movie model, and you'll ensure that the validation rules are | |
enforced any time a user attempts to create or edit a movie using the application. | |
Keeping Things DRY | |
One of the core design tenets of ASP.NET MVC is DRY ("Don't Repeat Yourself"). ASP.NET MVC encourages you | |
to specify functionality or behavior only once, and then have it be reflected everywhere in an application. This | |
reduces the amount of code you need to write and makes the code you do write less error prone and easier to | |
maintain. | |
The validation support provided by ASP.NET MVC and Entity Framework Code First is a great example of the | |
DRY principle in action. You can declaratively specify validation rules in one place (in the model class) and the | |
rules are enforced everywhere in the application. | |
Let's look at how you can take advantage of this validation support in the movie application. | |
Adding Validation Rules to the Movie Model | |
You'll begin by adding some validation logic to the Movie class. | |
Open the Movie.cs file. Add a using statement at the top of the file that references | |
theSystem.ComponentModel.DataAnnotations namespace: | |
usingSystem.ComponentModel.DataAnnotations; | |
Notice the namespace does not contain System.Web. DataAnnotations provides a built-in set of validation | |
attributes that you can apply declaratively to any class or property. | |
Now update the Movie class to take advantage of the built-inRequired,StringLength, andRange validation | |
attributes. Use the following code as an example of where to apply the attributes. | |
publicclassMovie{ | |
publicint ID {get;set;} | |
[Required] | |
publicstringTitle{get;set;} | |
[DataType(DataType.Date)] | |
publicDateTimeReleaseDate{get;set;} | |
[Required] | |
publicstringGenre{get;set;} | |
[Range(1,100)] | |
[DataType(DataType.Currency)] | |
publicdecimalPrice{get;set;} | |
[StringLength(5)] | |
publicstringRating{get;set;} | |
} | |
The validation attributes specify behavior that you want to enforce on the model properties they are applied to. | |
The Required attribute indicates that a property must have a value; in this sample, a movie has to have values | |
for the Title, ReleaseDate, Genre, and Price properties in order to be valid. The Range attribute constrains | |
a value to within a specified range. The StringLength attribute lets you set the maximum length of a string | |
property, and optionally its minimum length. Intrinsic types (such as decimal, int, float, DateTime) are | |
required by default and don't need the Requiredattribute. | |
Code First ensures that the validation rules you specify on a model class are enforced before the application | |
saves changes in the database. For example, the code below will throw an exception when the SaveChanges | |
method is called, because several required Movie property values are missing and the price is zero (which is out | |
of the valid range). | |
MovieDBContext db =newMovieDBContext(); | |
Movie movie =newMovie(); | |
movie.Title="Gone with the Wind"; | |
movie.Price=0.0M; | |
db.Movies.Add(movie); | |
db.SaveChanges();// <= Will throw validation exception | |
Having validation rules automatically enforced by the .NET Framework helps make your application more | |
robust. It also ensures that you can't forget to validate something and inadvertently let bad data into the | |
database. | |
Here's a complete code listing for the updated Movie.cs file: | |
usingSystem; | |
usingSystem.Data.Entity; | |
usingSystem.ComponentModel.DataAnnotations; | |
namespaceMvcMovie.Models{ | |
publicclassMovie{ | |
publicint ID {get;set;} | |
[Required] | |
publicstringTitle{get;set;} | |
[DataType(DataType.Date)] | |
publicDateTimeReleaseDate{get;set;} | |
[Required] | |
publicstringGenre{get;set;} | |
[Range(1,100)] | |
[DataType(DataType.Currency)] | |
publicdecimalPrice{get;set;} | |
[StringLength(5)] | |
publicstringRating{get;set;} | |
} | |
publicclassMovieDBContext:DbContext{ | |
publicDbSet<Movie>Movies{get;set;} | |
} | |
} | |
Validation Error UI in ASP.NET MVC | |
Re-run the application and navigate to the /Movies URL. | |
Click the Create New link to add a new movie. Fill out the form with some invalid values and then click the | |
Create button. | |
Notice how the form has automatically used a red border color to highlight the text boxes that contain invalid | |
data and has emitted an appropriate validation error message next to each one. The errors are enforced both | |
client-side (using JavaScript) and server-side (in case a user has JavaScript disabled). | |
A real benefit is that you didn't need to change a single line of code in theMoviesController class or in the | |
Create.cshtml view in order to enable this validation UI. The controller and views you created earlier in this | |
tutorial automatically picked up the validation rules that you specified by using validation attributes on the | |
properties of the Movie model class. | |
You might have noticed for the properties Title and Genre, the required attribute is not enforced until you | |
submit the form (hit the Create button), or enter text into the input field and removed it. For a field which is | |
initially empty (such as the fields on the Create view) and which has only the required attribute and no other | |
validation attributes, you can do the following to trigger validation: | |
1. Tab into the field. | |
2. Enter some text. | |
3. Tab out. | |
4. Tab back into the field. | |
5. Remove the text. | |
6. Tab out. | |
The above sequence will trigger the required validation without hitting the submit button. Simply hitting the | |
submit button without entering any of the fields will trigger client side validation. The form data is not sent to | |
the server until there are no client side validation errors. You can test this by putting a break point in the HTTP | |
Post method or using thefiddler tool or the IE 9F12 developer tools. | |
How Validation Occurs in the Create View and Create Action Method | |
You might wonder how the validation UI was generated without any updates to the code in the controller or | |
views. The next listing shows what the Create methods in the MovieController class look like. They're | |
unchanged from how you created them earlier in this tutorial. | |
// | |
// GET: /Movies/Create | |
publicActionResultCreate() | |
{ | |
returnView(); | |
} | |
// | |
// POST: /Movies/Create | |
[HttpPost] | |
publicActionResultCreate(Movie movie) | |
{ | |
if(ModelState.IsValid) | |
{ | |
db.Movies.Add(movie); | |
db.SaveChanges(); | |
returnRedirectToAction("Index"); | |
} | |
returnView(movie); | |
} | |
The first (HTTP GET) Create action method displays the initial Create form. The second ([HttpPost]) version | |
handles the form post. The second Create method (The HttpPost version) calls ModelState.IsValid to | |
check whether the movie has any validation errors. Calling this method evaluates any validation attributes that | |
have been applied to the object. If the object has validation errors, the Create method re-displays the form. If | |
there are no errors, the method saves the new movie in the database. In our movie example we are using, the | |
form is not posted to the server when their are validation errors detected on the client side; the second Create | |
method is never called. If you disable JavaScript in your browser, client validation is disabled and the HTTP | |
POST Create method calls ModelState.IsValid to check whether the movie has any validation errors. | |
You can set a break point in the HttpPost Create method and verify the method is never called, client side | |
validation will not submit the form data when validation errors are detected. If you disable JavaScript in your | |
browser, submit the form with errors, the break point will be hit. You still get full validation without JavaScript. | |
The following image shows how to disable JavaScript in the FireFox browser. | |
The following image shows how to disable JavaScript with the Chrome browser. | |
Below is the Create.cshtml view template that you scaffolded earlier in the tutorial. It's used by the action | |
methods shown above both to display the initial form and to redisplay it in the event of an error. | |
@model MvcMovie.Models.Movie | |
@{ | |
ViewBag.Title = "Create"; | |
} | |
<h2>Create</h2> | |
<scriptsrc="@Url.Content("~/Scripts/jquery.validate.min.js")"></script> | |
<scriptsrc="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")"></script> | |
@using (Html.BeginForm()) { | |
@Html.ValidationSummary(true) | |
<fieldset> | |
<legend>Movie</legend> | |
<divclass="editor-label"> | |
@Html.LabelFor(model => model.Title) | |
</div> | |
<divclass="editor-field"> | |
@Html.EditorFor(model => model.Title) | |
@Html.ValidationMessageFor(model => model.Title) | |
</div> | |
<divclass="editor-label"> | |
@Html.LabelFor(model => model.ReleaseDate) | |
</div> | |
<divclass="editor-field"> | |
@Html.EditorFor(model => model.ReleaseDate) | |
@Html.ValidationMessageFor(model => model.ReleaseDate) | |
</div> | |
<divclass="editor-label"> | |
@Html.LabelFor(model => model.Genre) | |
</div> | |
<divclass="editor-field"> | |
@Html.EditorFor(model => model.Genre) | |
@Html.ValidationMessageFor(model => model.Genre) | |
</div> | |
<divclass="editor-label"> | |
@Html.LabelFor(model => model.Price) | |
</div> | |
<divclass="editor-field"> | |
@Html.EditorFor(model => model.Price) | |
@Html.ValidationMessageFor(model => model.Price) | |
</div> | |
<divclass="editor-label"> | |
@Html.LabelFor(model => model.Rating) | |
</div> | |
<divclass="editor-field"> | |
@Html.EditorFor(model => model.Rating) | |
@Html.ValidationMessageFor(model => model.Rating) | |
</div> | |
<p> | |
<inputtype="submit"value="Create"/> | |
</p> | |
</fieldset> | |
} | |
<div> | |
@Html.ActionLink("Back to List", "Index") | |
</div> | |
Notice how the code uses an Html.EditorFor helper to output the<input> element for each Movie | |
property. Next to this helper is a call to the Html.ValidationMessageFor helper method. These two helper | |
methods work with the model object that's passed by the controller to the view (in this case, a Movie object). | |
They automatically look for validation attributes specified on the model and display error messages as | |
appropriate. | |
What's really nice about this approach is that neither the controller nor the Create view template knows | |
anything about the actual validation rules being enforced or about the specific error messages displayed. The | |
validation rules and the error strings are specified only in the Movie class. | |
If you want to change the validation logic later, you can do so in exactly one place by adding validation | |
attributes to the model (in this example, themovie class). You won't have to worry about different parts of the | |
application being inconsistent with how the rules are enforced — all validation logic will be defined in one | |
place and used everywhere. This keeps the code very clean, and makes it easy to maintain and evolve. And it | |
means that that you'll be fully honoring the DRY principle. | |
Adding Formatting to the Movie Model | |
Open the Movie.cs file and examine the Movie class. TheSystem.ComponentModel.DataAnnotations | |
namespace provides formatting attributes in addition to the built-in set of validation attributes. We've already | |
applied aDataType enumeration value to the release date and to the price fields. The following code shows the | |
ReleaseDate and Price properties with the appropriateDisplayFormat attribute. | |
[DataType(DataType.Date)] | |
publicDateTimeReleaseDate{get;set;} | |
[DataType(DataType.Currency)] | |
publicdecimalPrice{get;set;} | |
Alternatively, you could explicitly set aDataFormatString value. The following code shows the release date | |
property with a date format string (namely, "d"). You'd use this to specify that you don't want to time as part of | |
the release date. | |
[DisplayFormat(DataFormatString="{0:d}")] | |
publicDateTimeReleaseDate{get;set;} | |
The following code formats the Price property as currency. | |
[DisplayFormat(DataFormatString="{0:c}")] | |
publicdecimalPrice{get;set;} | |
The complete Movie class is shown below. | |
publicclassMovie{ | |
publicint ID {get;set;} | |
[Required] | |
publicstringTitle{get;set;} | |
[DataType(DataType.Date)] | |
publicDateTimeReleaseDate{get;set;} | |
[Required] | |
publicstringGenre{get;set;} | |
[Range(1,100)] | |
[DataType(DataType.Currency)] | |
publicdecimalPrice{get;set;} | |
[StringLength(5)] | |
publicstringRating{get;set;} | |
} | |
Run the application and browse to the Movies controller. The release date and price are nicely formatted. | |
In the next part of the series, we'll review the application and make some improvements to the automatically | |
generated Details and Delete methods. | |
Examining the Details and Delete Methods | |
In this part of the tutorial, you'll examine the automatically generated Details and Delete methods. | |
Examining the Details and Delete Methods | |
Open the Movie controller and examine the Details method. | |
publicActionResultDetails(int id =0) | |
{ | |
Movie movie =db.Movies.Find(id); | |
if(movie ==null) | |
{ | |
returnHttpNotFound(); | |
} | |
returnView(movie); | |
} | |
Code First makes it easy to search for data using the Find method. An important security feature built into the | |
method is that the code verifies that the Find method has found a movie before the code tries to do anything | |
with it. For example, a hacker could introduce errors into the site by changing the URL created by the links from | |
http://localhost:xxxx/Movies/Details/1 to something like http://localhost:xxxx/Movies/Details/12345 (or some | |
other value that doesn't represent an actual movie). If you did not check for a null movie, a null movie would | |
result in a database error. | |
Examine the Delete and DeleteConfirmed methods. | |
// GET: /Movies/Delete/5 | |
publicActionResultDelete(int id =0) | |
{ | |
Movie movie =db.Movies.Find(id); | |
if(movie ==null) | |
{ | |
returnHttpNotFound(); | |
} | |
returnView(movie); | |
} | |
// | |
// POST: /Movies/Delete/5 | |
[HttpPost,ActionName("Delete")] | |
publicActionResultDeleteConfirmed(int id =0) | |
{ | |
Movie movie =db.Movies.Find(id); | |
if(movie ==null) | |
{ | |
returnHttpNotFound(); | |
} | |
db.Movies.Remove(movie); | |
db.SaveChanges(); | |
returnRedirectToAction("Index"); | |
} | |
Note that the HTTP Get Delete method doesn't delete the specified movie, it returns a view of the movie | |
where you can submit (HttpPost) the deletion.. Performing a delete operation in response to a GET request (or | |
for that matter, performing an edit operation, create operation, or any other operation that changes data) | |
opens up a security hole. For more information about this, see Stephen Walther's blog entryASP.NET MVC Tip | |
#46 — Don't use Delete Links because they create Security Holes. | |
The HttpPost method that deletes the data is named DeleteConfirmed to give the HTTP POST method a | |
unique signature or name. The two method signatures are shown below: | |
// GET: /Movies/Delete/5 | |
publicActionResultDelete(int id =0) | |
// | |
// POST: /Movies/Delete/5 | |
[HttpPost,ActionName("Delete")] | |
publicActionResultDeleteConfirmed(int id =0) | |
The common language runtime (CLR) requires overloaded methods to have a unique signature (same method | |
name but different list of parameters). However, here you need two Delete methods -- one for GET and one for | |
POST -- that both have the same signature. (They both need to accept a single integer as a parameter.) | |
To sort this out, you can do a couple of things. One is to give the methods different names. That's what the | |
scaffolding mechanism did in he preceding example. However, this introduces a small problem: ASP.NET maps | |
segments of a URL to action methods by name, and if you rename a method, routing normally wouldn't be able | |
to find that method. The solution is what you see in the example, which is to add the ActionName("Delete") | |
attribute to theDeleteConfirmed method. This effectively performs mapping for the routing system so that a | |
URL that includes /Delete/ for a POST request will find the DeleteConfirmed method. | |
Another common way to avoid a problem with methods that have identical names and signatures is to | |
artificially change the signature of the POST method to include an unused parameter. For example, some | |
developers add a parameter typeFormCollectionthat is passed to the POST method, and then simply don't | |
use the parameter: | |
publicActionResultDelete(FormCollection fcNotUsed,int id =0) | |
{ | |
Movie movie =db.Movies.Find(id); | |
if(movie ==null) | |
{ | |
returnHttpNotFound(); | |
} | |
db.Movies.Remove(movie); | |
db.SaveChanges(); | |
returnRedirectToAction("Index"); | |
} | |
Wrapping Up | |
You now have a complete ASP.NET MVC application that stores data in a SQL Server Compact database. You | |
can create, read, update, delete, and search for movies. | |
This basic tutorial got you started making controllers, associating them with views, and passing around hard- | |
coded data. Then you created and designed a data model. Entity Framework code-first created a database from | |
the data model on the fly, and the ASP.NET MVC scaffolding system automatically generated the action | |
methods and views for basic CRUD operations. You then added a search form that let users search the | |
database. You changed the database to include a new column of data, and then updated two pages to create | |
and display this new data. You added validation by marking the data model with attributes from the | |
DataAnnotations namespace. The resulting validation runs on the client and on the server. | |
If you'd like to deploy your application, it's helpful to first test the application on your local IIS 7 server. You can | |
use thisWeb Platform Installer link to enable IIS setting for ASP.NET applications. See the following deployment | |
links: | |
• ASP.NET Deployment Content Map | |
• | |
Enabling IIS 7.x | |
• Web Application Projects Deployment | |
I now encourage you to move on to our intermediate-levelCreating an Entity Framework Data Model for an | |
ASP.NET MVC Application andMVC Music Store tutorials, to explore theASP.NET articles on MSDN, and to | |
check out the many videos and resources athttp://asp.net/mvc to learn even more about ASP.NET MVC! The | |
ASP.NET MVC forums are a great place to ask questions. | |
Enjoy! | |
— Rick Anderson blogs.msdn.com/rickAndy twitter @RickAndMSFT | |
— Scott Hanselmanhttp://www.hanselman.com/blog/ twitter @shanselman | |