Lets assume, we have following simple webform page with single button:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApp.Pages.Tr.WebForm1" %>

<asp:Button runat="server" OnClick="btn_Click" />

And codebehind:

public partial class WebForm1 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        /*some behavior*/
    }

    protected void btn_Click(object sender, EventArgs e)
    {
         /*some behavior*/
    }
}

Now, lets assume we have some special customer, who requires some additional special actions when clicking button.

I would like to achieve it by writing inherited class – something like:

public class SpecialWebForm : WebForm1
{
    override void btn_Click(object sender, EventArgs e)
    {
        base.btn_Click(object sender, EventArgs e);
        /*special behavior*/
    }
}

Is it possible to dynamically select implementation of codebehind class? To make somewhere something like:

if (IsSpecial(CurrentClient))
{
    WebForm1.CodeBehind = new SpecialWebForm();
}

or something like that?