Now that Visual Studio 2008 and C# 3.0 is out all the talk in the blogosphere is about what is still missing and what we want in the next version. And mixins are high on the list.
Mixins could be implemented elegantly by extending generics so you can use them for inheritance like this;
1: class Mixin<T> : T {
2: public void MixinMethod() {
3: // ...
4: }
5: }
By allowing to inherit from T you can use Mixin to extend any none sealed type like this
1: var mixinString = new Mixin<string>;
2: mixinString.MixinMethod();
It's a pity Anders Hejlsberg doesn't read my blog.