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Converting a Web Forms Page to a User Control

If you have developed a Web Forms page and decide you would like to access its functionality throughout your application, you can make some minor alterations to the file to change it to a user control. Since the <html>, <body>, and <form> elements are not included in user controls, you must include these elements in the containing Web Forms page.

CAUTION   If you are developing a user control in a code-behind class, you must extend the UserControl class rather than the Page class. For more information, see Developing User Controls in a Code-Behind File.

To convert a Web Forms page into a user control

  1. Remove all <html>, <body>, and <form> elements from the page. The following example illustrates this conversion.

    Initial Web Forms page:

    <html>
    <script language="VB" 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>Web Forms Page</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>
    
    [C#]
    <html>
    <script language="C#" runat=server>
    void EnterBtn_Click(Object Sender, EventArgs E){
       Label1.Text = "Hi " + Name.Text + " welcome to ASP.NET!";
    }
    </script>
    <body>
    <h3>Web Forms Page</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>
    

    The user control, following the conversion:

    <h3> <u>User Control</u> </h3>
    <script language="VB" 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/>
    
    [C#]
    <h3>User Control</h3>
    <script language="C#" 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/>
    
  2. If there is an @ Page directive in the Web Forms page, change it to an @ Control directive.
    Note   To avoid parser errors when you convert a page to a user control, remove any attributes supported by the @ Page directive that are not supported by the @ Control directive. For more information, see Directive Syntax.
  3. Include a className attribute in the @ Control directive. This allows the user control to be strongly typed when it is added to a page or other server controls programmatically.
  4. Give the control a file name that reflects how you plan to use it and change the file name extension from .aspx to .ascx.

See Also

Web Forms User Controls | Including a User Control in a Web Forms Page | Creating a User Control | Sever Event Handling in Web Forms Pages | Handling User Control Events

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