Replacing an asp control at runtime

I have an existing .NET 1.1 dll that I do not have the source code for. It contains the code-behind for a asp.net page containing 开发者_Python百科various form controls including a third party text editor that I no longer want to use. I want to replace the text editor with a simple asp:Textbox but the existing textbox is baked into the old assembly. How can I override / extend the existing page to use a textbox instead of the old text editor control?

As far as I'm aware we can't get that textbox replaced with your own without modifying the dll.

If I'm in your place I would have used .net reflector and used same code to recreate the new dll with the textbox functionality which you want to embed.