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INFO: ASP.NET Code-Behind Model Overview

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Article ID:303247
Last Review:February 23, 2007
Revision:3.3
This article was previously published under Q303247
This article refers to the following Microsoft .NET Framework Class Library namespace:
•System.Web.UI
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SUMMARY

This article provides a brief overview of the code-behind model, which is introduced in ASP.NET.

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MORE INFORMATION

ASP.NET supports two methods to author pages:
•In-line code
•Code-behind

In-Line Code

In-line code is code that is embedded directly within the ASP.NET page. The following code represents a sample ASP.NET page that includes in-line code:

Myinlinecode.aspx
<%@ Language=C# %>
<HTML>
   <script runat="server" language="C#">
   void MyButton_OnClick(Object sender, EventArgs e)
   {
      MyLabel.Text = MyTextbox.Text.ToString();
   }
   </script>
   <body>
      <form id="MyForm" runat="server">
         <asp:textbox id="MyTextbox" text="Hello World" runat="server"></asp:textbox>
         <asp:button id="MyButton" text="Echo Input" OnClick="MyButton_OnClick" runat="server"></asp:button>
         <asp:label id="MyLabel" runat="server"></asp:label>
      </form>
   </body>
</HTML>

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Code-Behind

Code-behind refers to code for your ASP.NET page that is contained within a separate class file. This allows a clean separation of your HTML from your presentation logic. The following sample illustrates an ASP.NET code-behind page:

MyCodebehind.aspx
<%@ Language="C#" Inherits="MyStuff.MyClass" %>
<HTML>
    <body>
        <form id="MyForm" runat="server">
        <asp:textbox id="MyTextBox" text="Hello World" runat="server"></asp:textbox>
        <asp:button id="MyButton" text="Echo Input" Onclick="MyButton_Click" runat="server"></asp:button>
        <asp:label id="MyLabel" runat="server" />
        </form>
    </body>
</HTML>
Mycodebehind.cs
using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace MyStuff
{
    public class MyClass : Page
    {
        protected System.Web.UI.WebControls.Label MyLabel;
        protected System.Web.UI.WebControls.Button MyButton;
        protected System.Web.UI.WebControls.TextBox MyTextBox;

        public void MyButton_Click(Object sender, EventArgs e)
        {
            MyLabel.Text = MyTextBox.Text.ToString();
        }
    }
}
In the preceding sample, you can use the following syntax to compile Mycodebehind.cs:
csc.exe /out:mycodebehind.dll /t:library mycodebehind.cs
When you use the following code, the code-behind page inherits from the Page class. The Page class resides in the System.Web.UI namespace: 
public class MyClass : Page
Inheriting from the Page class gives the code-behind page access to the ASP.NET intrinsic objects, such as Request and Response. In addition, inheriting from the Page class provides a framework for handling events for controls within the ASP.NET page.

In the preceding sample, the code-behind page is compiled before ASP.NET runs. Alternatively, you can reference the code-behind class by using an SRC tag as follows: 
<%@ Language="C#" Inherits="MyStuff.MyClass" src="MyCodebehind.cs" %>
In this case, ASP.NET compiles the code-behind page on the fly. Notice that this compilation step only occurs when the code-behind file is updated (which is detected through a timestamp change).

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Code-Behind Support in Visual Studio .NET

When you use Microsoft Visual Studio .NET to create ASP.NET Web Forms, code-behind pages are the default method. In addition, Visual Studio .NET automatically performs precompilation for you when you build your solution. Note that code-behind pages that are created in Visual Studio .NET include a special page attribute, Codebehind, which Visual Studio .NET uses.

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REFERENCES

For additional information%1, click the article number%2 below to view the article%2 in the Microsoft Knowledge Base:
313105 (http://support.microsoft.com/kb/313105/EN-US/) BUG: Cannot Compile Code-Behind Files That Use Src Attribute on a UNC Share

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APPLIES TO
•Microsoft ASP.NET 1.1
•Microsoft ASP.NET 1.0

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Keywords: 
kbinfo kbwebforms KB303247

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