I just built a sample that shows how to use TX Text Control .NET for Windows Forms in a Windows Presentation Foundation application with .NET 3.0 in Visual Studio 2005. I prepared a step-by-step guide for you to test on your own. Microsoft provides a really nice 'interop' class, the WindowsFormsIntegration assembly that makes this approach effortlessly.
This article guides you through all necessary steps to create your first TX Text Control .NET for Windows Forms based WPF application. Read the full article here:
Feel free to contact me, if you have additional questions or comments.