When I first saw Shaun Sullivan’s code to create a .NET plugin in Raiser’s Edge I was a bit concerned. I tried out the code and after a bit of fiddling with it I managed to get it to work. Although I thought and still think that having an extra HTML page with the plugin as a user control was a bit of a hassle.
A much easier solution that I have done several times is to simply create a .NET class library with a form. When you start your plugin the form is shown directly in a new window.