Qt# is a set of classes that bind the C# language to the Qt toolkit. The bindings are in Alpha phase right now, but development is moving quickly. The bindings require the Mono runtime and compiler suite.
Qt# bindings home page.
C# bindings to Qt with KDE bindings on the way. The bindings consist of 476 wrapped Qt classes with full support for custom widgets and slots, so you can make your own widgets! The syntax of the bindings are very close to the original C++, but with all the extra syntactical sugar C# provides :-)
Mono is an open source implementation of the .NET Development Framework.
Screenshots of Qt# in action!
Download Qt# here.