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How to: Convert Web Forms Pages into ASP.NET User Controls

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If you have developed an ASP.NET Web page and would like to access its functionality throughout your application, you can make some minor alterations to the page to change it to a user control.

To convert a single-file ASP.NET Web page into a user control

  1. Rename the control so the file name extension is .ascx.

  2. Remove the html, body, and form elements from the page.

  3. Change the @ Page directive to an @ Control directive.

  4. Remove all attributes of the @ Control directive except Language, AutoEventWireup (if present), CodeFile, and Inherits.

  5. Include a className attribute in the @ Control directive. This allows the user control to be strongly typed when it is added to a page.

To convert a code-behind ASP.NET Web page into a user control

  1. Rename the .aspx file so the file name extension is .ascx.

  2. Rename the code-behind file to have the file name extension .ascx.vb or .ascx.cs, depending on what programming language the code-behind file is in.

  3. Open the code-behind file and change the class from which it inherits from Page to UserControl.

  4. In the .aspx file, do the following:

    1. Remove the html, body, and form elements from the page.

    2. Change the @ Page directive to an @ Control directive.

    3. Remove all attributes of the @ Control directive except Language, AutoEventWireup (if present), CodeFile, and Inherits.

    4. In the @ Control directive, change the CodeFile attribute to point to the renamed code-behind file.

  5. Include a className attribute in the @ Control directive. This allows the user control to be strongly typed when it is added to a page.

Example

The following example shows a single-file ASP.NET Web page in its original form and the resulting user control after converting the page.

Security noteSecurity Note

This example has a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview.

 
<%@ Page Language="VB" %>
<html>
<script runat=server>
Sub EnterBtn_Click(sender as Object, e as EventArgs)
    Label1.Text = "Hi " & Name.Text & " welcome to ASP.NET!"
End Sub
</script>
<body>
<h3> <u>Web Forms Page</u> </h3>
<form>
    Enter Name: <asp:textbox id="Name" runat=server/>
    <asp:button Text="Enter" OnClick="EnterBtn_Click"
        runat=server/>
<br>
<br>
<asp:label id="Label1" runat=server/>
</form>
</body>
</html>

<%@ Page Language="C#" %>
<html>
<script runat=server>
void EnterBtn_Click(Object sender, EventArgs e)
{
    Label1.Text = "Hi " + Name.Text + " welcome to ASP.NET!";
}
</script>
<body>
<h3> <u>Web Forms Page</u> </h3>
<form>
Enter Name: <asp:textbox id="Name" runat=server/>
<asp:button Text="Enter" OnClick="EnterBtn_Click"
    runat=server/>
<br>
<br>
<asp:label id="Label1" runat=server/>
</form>
</body>
</html>

<%@ Control Language="VB" ClassName="SampleUserControl" %>
<h3> <u>User Control</u> </h3>
<script runat=server>
Sub EnterBtn_Click(sender as Object, e as EventArgs)
    Label1.Text = "Hi " & Name.Text & " welcome to ASP.NET!"
End Sub
</script>
Enter Name: <asp:textbox id="Name" runat=server/>
<asp:button Text="Enter" OnClick="EnterBtn_Click"
    runat=server/>
<br>
<br>
<asp:label id="Label1" runat=server/>

<%@ Control Language="C#" ClassName="SampleUserControl" %>
<h3> <u>User Control</u> </h3>
<script runat=server>
void EnterBtn_Click(Object Sender, EventArgs e)
{
    Label1.Text = "Hi " + Name.Text + " welcome to ASP.NET!";
}
</script>
Enter Name: <asp:textbox id="Name" runat=server/>
<asp:button Text="Enter" OnClick="EnterBtn_Click"
runat=server/>
<br>
<br>
<asp:label id="Label1" runat=server/>

See Also

Tasks

How to: Create an ASP.NET User Control

Concepts

ASP.NET User Controls Overview