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ASP.NET Code-behind model overview

  • Article

This article provides a brief overview of the in-line code and Code-behind model in ASP.NET.

Original product version:   ASP.NET
Original KB number:   303247

Summary

This article refers to the Microsoft .NET Framework class library namespace System.Web.UI.

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>

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. This compilation step only occurs when the code-behind file is updated (which is detected through a timestamp change).

Code-behind support in Visual Studio .NET

When you use Visual Studio .NET to create ASP.NET Web Forms, code-behind pages are the default method. In addition, Visual Studio .NET automatically performs pre-compilation for you when you build your solution.

Note

Code-behind pages that are created in Visual Studio .NET include a special page attribute, Code-behind, which Visual Studio .NET uses.