ASP.NET MVC- VIEW Overview Part 1

  The purpose of this tutorial is to  provide you with a brief introduction to ASP.NET MVC views, view data,  and HTML Helpers. By the end of this tutorial, you should understand  how to create new views, pass data from a controller to a view, and  use HTML Helpers to generate content in a view.

  Understanding Views

  For ASP.NET or Active Server Pages,  ASP.NET MVC does not include anything that directly corresponds to a  page. In an ASP.NET MVC application, there is not a page on disk that  corresponds to the path in the URL that you type into the address bar  of your browser. The closest thing to a page in an ASP.NET MVC application  is something called a view.

  ASP.NET MVC application, incoming  browser requests are mapped to controller actions. A controller action  might return a view. However, a controller action might perform some  other type of action such as redirecting you to another controller action.

  Listing 1 contains a simple controller  named the HomeController. The HomeController exposes two controller  actions named Index() and Details().

  Listing 1  - HomeController.cs

using System.Web.Mvc;



namespace MvcApplication1.Controllers

{

    [HandleError]

    public class HomeController : Controller

    {

        public ActionResult Index()

        {

            return View();

        }



        public ActionResult Details()

        {

            return RedirectToAction("Index");

        }

    }

}

 

  You can invoke the first action, the  Index() action, by typing the following URL into your browser address  bar:

      /Home/Index

  You can invoke the second action, the  Details() action, by typing this address into your browser:

      /Home/Details

  The Index() action returns a view.  Most actions that you create will return views. However, an action can  return other types of action results. For example, the Details() action  returns a RedirectToActionResult that redirects incoming request to  the Index() action.

The Index() action contains the following  single line of code: View();

  This line of code returns a view that  must be located at the following path on your web server:

      \Views\Home\Index.aspx

  The path to the view is inferred from  the name of the controller and the name of the controller action.

  If you prefer, you can be explicit  about the view. The following line of code returns a view named  Fred :

    View( Fred );

  When this line of code is executed,  a view is returned from the following path:

      \Views\Home\Fred.aspx

  Adding Content  to a View

  A view is a standard (X)HTML document  that can contain scripts. You use scripts to add dynamic content to  a view.For example, the view in Listing 2  displays the current date and time.

  Listing 2  - \Views\Home\Index.aspx

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



<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">



<html xmlns="http://www.w3.org/1999/xhtml" >

<head id="Head1" runat="server">

    <title>Index</title>

</head>

<body>

    <div>

    

        

    The current date and time is

    <% Response.Write(DateTime.Now);%>



    

    </div>

</body>

</html>

 Notice that the body of the HTML page  in Listing 2 contains the following script:

    <% Response.Write(DateTime.Now);%>

You use the script delimiters <%  and %> to mark the beginning and end of a script. This script is  written in C#. It displays the current date and time by calling the  Response.Write() method to render content to the browser. The script  delimiters <% and %> can be used to execute one or more statements.

Since you call Response.Write() so  often, Microsoft provides you with a shortcut for calling the Response.Write()  method. The view in Listing 3 uses the delimiters <%= and %> as  a shortcut for calling Response.Write().

  Listing 3 - Views\Home\Index2.aspx

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



<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">



<html xmlns="http://www.w3.org/1999/xhtml" >

<head id="Head1" runat="server">

    <title>Index</title>

</head>

<body>

    <div>

    

        

    The current date and time is

    <%=DateTime.Now %>



    

    </div>

</body>

</html>

  You can use any .NET language to generate  dynamic content in a view. Normally, you�ll use either Visual Basic  .NET or C# to write your controllers and views.

  Using HTML Helpers  to Generate View Content

  You use view data to pass data from  a controller to a view. Think of view data like a package that you send  through the mail. All data passed from a controller to a view must be  sent using this package. For example, the controller in Listing 6 adds  a message to view data.

  Listing 6 - ProductController.cs

  

using System.Web.Mvc;



namespace MvcApplication1.Controllers

{

    public class ProductController : Controller

    {

        public ActionResult Index()

        {

            ViewData["message"] = "Hello World!";

            return View();

        }



    }

}

  The controller ViewData property represents  a collection of name and value pairs. In Listing 6, the Index() method  adds an item to the view data collection named message with the value  Hello World! . When the view is returned by the Index() method,  the view data is passed to the view automatically.

  The view in Listing 7 retrieves the  message from the view data and renders the message to the browser.

  Listing 7 -- \Views\Product\Index.aspx

  

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



<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

<head id="Head1" runat="server">

    <title>Product Index</title>

</head>

<body>

    <div>

    

    <%= Html.Encode(ViewData["message"]) %>

    

    </div>

</body>

</html>

  Notice that the view takes advantage  of the Html.Encode() HTML Helper method when rendering the message.  The Html.Encode() HTML Helper encodes special characters such as <  and > into characters that are safe to display in a web page. Whenever  you render content that a user submits to a website, you should encode  the content to prevent JavaScript injection attacks.

  (Because we created the message ourselves  in the ProductController, we don't really need to encode the message.  However, it is a good habit to always call the Html.Encode() method  when displaying content retrieved from view data within a view.)

  In Listing 7, we took advantage of  view data to pass a simple string message from a controller to a view.  You also can use view data to pass other types of data, such as a collection  of database records, from a controller to a view. For example, if you  want to display the contents of the Products database table in a view,  then you would pass the collection of database records in view data.

  You also have the option of passing  strongly typed view data from a controller to a view. We explore this  topic in the tutorial Understanding Strongly Typed View Data and  Views.

  Summary

  This tutorial provided a brief introduction  to ASP.NET MVC views, view data, and HTML Helpers. In the first section,  you learned how to add new views to your project. You learned that you  must add a view to the right folder in order to call it from a particular  controller. Next, we discussed the topic of HTML Helpers. You learned  how HTML Helpers enable you to easily generate standard HTML content.  Finally, you learned how to take advantage of view data to pass data  from a controller to a view.

 

 

  原文网址:http://www.asp.net/mvc/tutorials/older-versions/views/asp-net-mvc-views-overview-cs

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