We're considering converting our WinForms application to a WPF application. Part of the reason is that WPF/XAML seem to be the future. We are also using third party controls that we would like to be able to phase out. Making this conversion seems like a pretty big and time consuming undertaking, though. Would it make sense to develop XAML controls that could be used in our WinForms application as a first step in the process? My thinking is that the same controls would then be used in the WPF application and all of the look, feel, and functionality would be built into the controls in either environment.
Have you considered doing it the other way round? If your end goal is to convert to WPF completely, you could start by setting up WPF application which hosts your WinForms control. Then you could replace WinForms controls one by one over time. WPF can be quite different from WinForms and you might want to tackle some architectural issues first such as navigation.
The preferred pattern for building WPF apps is Model-View-ViewModel. I suggest doing some prototyping to get to know it if you aren't familiar with it.