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?

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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.