From KDE TechBase

Qt# is a set of classes that bind the C# language to the Qt toolkit. The bindings are in active development.

The Qyoto/Kimono project were SMOKE based bindings which use the mono C# compiler for use with Qt and KDE that are very similar to C++/Qt syntax but with the addition of the unique syntactic constructs of C#. Because .NET is a multi-language VM, a variety of languages should be able to access the bindings. The Qyoto binding is no longer in development.

Mono is an open source implementation of the .NET Development Framework.

Mono Concerns

RMS on Mono