wx.NET is a C# wrapper for wxWidgets (www.wxwidgets.org), providing a portable GUI toolkit for .NET programs. Supported on Windows, Linux GTK, and Mac OS X using MS.NET or Mono. Visit wxnet.sf.net or click "Project Home Page" below to learn more.
Wxnet works excellent.
I am a fan of WxWidgets, and this .NET version is a very good thing ! It seems that it's lacking some features for now (GCDC !!), but this is a very nice project !