ASP.NET MVC深入探索：从基础到高级实践

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"ASP.NET MVC系列图书《ASP.NET MVC in Action》" 本书是关于ASP.NET MVC框架的详细指南，旨在帮助读者深入理解并掌握这一技术。ASP.NET MVC是一个用于构建动态网站的开源框架，它提供了模型-视图-控制器（MVC）设计模式的实现，使开发者能够更清晰地分离关注点，提高代码的可测试性和可维护性。 1. ASP.NET MVC框架概述 ASP.NET MVC框架是微软推出的一种轻量级、基于约定的Web应用程序开发框架，它允许开发者使用HTML、CSS和JavaScript等技术来创建具有高度控制力的用户界面，同时利用C#或VB.NET等编程语言处理业务逻辑和数据访问。 2. 系统需求要运行ASP.NET MVC应用程序，你需要安装以下组件： - .NET Framework：ASP.NET MVC依赖于特定版本的.NET Framework，通常与Visual Studio版本匹配。 - Visual Studio：用于编写和调试代码，虽然可以使用其他编辑器，但Visual Studio提供了完整的集成开发环境（IDE）支持。 - IIS或IIS Express：作为Web服务器，托管ASP.NET MVC应用。 3. 开始使用ASP.NET MVC - 启动项目：通过Visual Studio创建一个ASP.NET MVC项目，你可以运行提供的starter project，了解基本结构和工作流程。 - "Hello, World"示例：书中逐步介绍从简单的"Hello, World"程序开始，演示如何创建控制器、动作方法以及返回视图。 4. 强类型视图强类型视图是ASP.NET MVC的一个关键特性，它允许在视图中直接使用模型对象，确保在编译时捕获错误，而不是在运行时。视图通过@model指令声明使用的模型类型，这样可以在视图中直接访问模型的属性。 5. 路由基础知识 ASP.NET MVC的路由系统负责将HTTP请求映射到控制器的动作。开发者可以自定义路由规则，指定URL模式与控制器和动作之间的映射，从而实现更灵活的URL设计，提高用户体验。 6. 进一步学习随着内容的深入，书中的后续章节会探讨如何扩展和定制ASP.NET MVC框架，包括处理复杂网站架构、利用现有ASP.NET功能（如身份验证和授权）、实现AJAX交互、部署策略，以及比较ASP.NET MVC与其他类似框架（如MonoRail和Ruby on Rails）的异同。这本书适合有一定ASP.NET基础，希望转而使用MVC模式开发Web应用的开发者，无论你是新手还是经验丰富的开发者，都能从中获得宝贵的指导和启发。通过学习，你将能够构建出高效、可扩展且易于维护的Web应用程序。

}

Notice that the public

Index

action method is all that is necessary for this controller to be web-callable.

Simple content action methods need not return

ActionResult

. Returning any other type will result in that object

being rendered as content to the response stream.

If we point our browser to

/HelloWorld2, we'll see that our controller sends exactly the same response to the

browser as shown in figure 1.7 Now that we know how to craft a controller, we will explore our first view.

Figure 1.7 Notice the web page has the same output as before. The end result is the same even though the controller

implementation has evolved.

1.3 Our First View

Recall that the ASP.NET MVC Framework uses a convention for locating views. The convention is to find an .aspx

file in a directory tree that matches /Views/controllername/actionname.aspx. In our next example, we will modify

our controller a bit by calling a method on the

Controller

base class called

View()

. We'll set the model, which

is a

string

with the text, "Hello World", to an entry in the

ViewDataDictionary

object on the

ViewData

property of the

Controller

base class. This

ViewDataDictionary

instance will be forwarded to the view.

Although ViewData is a ViewDataDictionary we recommend you only depend on the IDictionary<object, object>

interface if you are replacing the view engine. View engines will be discussed in more detail in chapter 4. Below,

in our example, we see that our action returns ActionResult instead of void. After an action method returns, the

ActionResult executes to perform the appropriate behavior, which is rendering a view in this case. Examine listing

1.9 for the current implementation of our controller.

ViewData

contains the object that will be forwarded on to

the view. The

View()

method also supports passing a single object to the view that is then accessible via

ViewData.Model

, which we will explore later.

Listing 1.9 Using a view to render the model.

using System.Web.Mvc;

namespace MvcApplication.Controllers

{

public class HelloWorld3Controller : Controller

{

public ActionResult Index()

{

//Adding objects to view data allows the framework

//to pass them to the view

ViewData.Add("text", "Hello World3");

return View();

}

Listing 1.10 A simple view. Note how we extract the object passed from the controller from the ViewData

dictionary.

<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage" %>

<%--/Views/HelloWorld3/Index.aspx --%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

</head>

<body>

<div>

</div>

</body>

</html>

The flow from our controller to or view is very, very simple. The controller designates one or many objects to

be forwarded to the view and then declares the name of the view. The MVC Framework will locate the view,

instantiate it, push in the ViewData, and have the view render itself to the response stream. The

ViewPage

base

class fully supports rendering, but ViewState, postbacks, and the server-side post-back events no longer happen.

Rendering events still fire, however since ViewPage derives from

System.Web.UI.Page

. The view’s responsibility

is to transform objects passed to it into HTML. This is a very key part of the Separation of Concerns that Microsoft

is focusing on for this product. The controller does not know how the view is doing the formatting. The only point

of coupling is that the controller names the view. It does not matter that the

System.Web.Mvc.WebFormViewEngine

is executing. The same controller could function quite well with an

NVelocity view (supported in MvcContrib) since the controller's only coupling to the view is the view name. For

now, we will forward "Hello World3" to the view, and figure 1.10 shows the rendered page. This example has

shown how to get a simple case working, but there are maintenance concerns you should be aware of while

building an application with this framework.

Figure 1.10 Although we are using a complete view, the output is the same as previous examples, except now, we have a full HTML

page and not just an HTML fragment.

1.4 Ensuring the application is maintainable

You might have cringed when you saw that the domain model object was being pushed into an

IDictionary

with

string

key as the way to identify the object in the view. .Net has conditioned us to want everything to be

strongly-typed, so string identifiers are sometimes viewed as a negative. That point is subjective and

controversial, and you have several options depending on your preferences. The use of an

IDictionary<object, object>

for ViewData is the default mechanism in the

Controller

base class. As the

number of objects forwarded to the view increase, it is easy to create some helpers in the view to avoid casting

operations everywhere. Many controllers will only forward one object to the view, and for those cases, we can

make use of the

ViewData.Model

property as well as strongly-typed views. For our next example, we will make

a small change to our controller and view to enable a strongly-typed reference. Listing 1.11 shows our controller

discarding the use of the

IDictionary<object, object>

and passing domain model object directly to the

View()

method. This works well for many scenarios, and it even scales to large application with the use of a

"view model", which is a presentation object specifically crafted for use in a single view. For composed views using

ViewData

as a dictionary may is necessary, but partial views, covered in chapter 4, can also provide for composed

views.

For this view, since our model is a

string

, the only difference is the lack of the need to call

ToString()

the view. Note in listing 1.11 the simplified rendering. If I want to call

ToLower()

to ensure the text was

lowercase, I'd get intellisense and API checking. For this view, we are also using a master page.

Listing 1.11 Passing in the presentation model to the RenderView method

using System.Web.Mvc;

namespace MvcApplication.Controllers

{

public class HelloWorld4Controller : Controller

{

public ActionResult Index()

{

//casting to an object to ensure correct

//overload is called

return View((object)"Hello World4");

}

Listing 1.12 Strongly typed view with master page.

<%@ Page Inherits="System.Web.Mvc.ViewPage<string>"

MasterPageFile="~/Views/Shared/HelloWorld.Master"%>

<%@ Import Namespace="MvcApplication.Controllers"%>

<asp:Content ID="Content2" ContentPlaceHolderID="Main" runat="server">

<h1><%=Model %>! I'm strongly typed in a layout!</h1>

</asp:Content>

Notice that we have a

Model

property available that is the type declared in the Inherits tag. In listing 1.12 we

have chosen

System.Web.Mvc.ViewPage<T>

. The generic base class allows us to strongly-type the

ViewData

property because the

ViewData

property is of type

ViewDataDictionary<T>

, and the

Model

property is of

type

In this example, the view has chosen the master page, but you can also choose the master inside the controller

action. It is up to you, but not all view engines support the view specifying the master. Master pages function

exactly the same as in Web Forms for templating, but the server side postback and

ViewState

mechanism are

irrelevant. Rendering is the only responsibility of the view and the master page. Listing 1.13 shows our master

page, which outlines the structure for the page. The layout declares

System.Web.MVC.ViewMasterPage

as the

base type.

Listing 1.13 The layout for our view. The purpose is to provide the layout structure for the view. Be sure not

to put any behavior here.

<%@ Master Language="C#" AutoEventWireup="true"

Inherits="System.Web.Mvc.ViewMasterPage" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<title>Hello!!</title>

<asp:ContentPlaceHolder ID="head" runat="server">

</asp:ContentPlaceHolder>

</head>

<body>

<asp:ContentPlaceHolder ID="Main" runat="server">

</asp:ContentPlaceHolder>

</div>

</body>

</html>

If we point our browser to

/HelloWorld4

, we see our strongly-typed view and master page in action. To make it

stand out, we have given it a strong, red border as shown in figure 1.11. Most views that we will work with in this

book will use the

ViewPage<T>

base class to enable a strongly-typed

Model

property and the easy usage of view

models, which will be covered in chapter 2.

Figure 1.11. This is our final view, complete with layout, strong typing and a little CSS to spice it up.

Congratulations! You have created your first controller, and it handles its responsibility perfectly. From this

point forward, we will not cover every small step of developing with the MVC Framework. If you are reading this

book, you are already well-versed in ASP.NET, so we will merely be covering the items that are new with the

ASP.NET MVC Framework. We will be using best practices and advanced software development techniques

throughout the examples. The first important practice is unit testing. Because the MVC Framework allows us to

keep our screen controllers separated from the views, we can now test the controlling logic very easily. We

consider testing part of getting started with the MVC Framework, we will cover it now and keep a strong emphasis

on testing throughout this book. Although we will not print every unit test in the book, you can find more unit

tests in the examples available with the book.

1.5 Testing Controller Classes

Turn back to the Visual Studio solution to the unit test project that already exists there. Because Visual Studio

does not come with NUnit, you will need to add your own reference to NUnit or your unit testing framework of

choice. Because MSTest now comes in the Professional sku, the project will come with a reference to MSTest. We

have removed that reference and opted for the more widely used tool, NUnit. We have created a class named

HelloWorld4ControllerTester

to house the unit tests that verify it functions correctly. See in figure 1.12

that we are grouping controller unit test fixtures in a

Controllers

folder. We will continue to group like fixtures.

Browse through the following code listings. You will notice that we have created stubs for several classes that the

controller needs to function. This unit test example is the simplest one we will see in this book. Listing 1.14 depicts

the NUnit test fixture for

HellowWorld4Controller

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