.NET wish list...

• Generics that can support 'text-like' replacement at runtime, where you can basically say that "I know that type T actually has a method called Foo with the signature bool Foo(int) but may not implement some particular interface (since you may not control the implementation of T)". I'd like to be able to call Foo from my generic class even if I can't change T to implement an interface that supports Foo. I'm thinking something like:

  public static void DoSomething(T target)
      where T: class having bool Foo(int)
  {
      if(target.Foo(0))
          Console.WriteLine("Woohoo");
  }

• A way of marking objects that MUST be used in a 'using' expression (i.e. they only make sense there) and having the C# compiler enforce it. For instance, an attribute would work for me (similar to how 'FlagsAttribute' indicates special semantics on enums). My reasoning for this is that I'd like to use IDisposable for some C++-style RAII-like stuff, but there's no way to guarantee that the objects are used correctly.
• A way of injecting simple code / hooking "before" and "after" property notifications on 'automatic properties' in C#. For instance, if I do an automatic property, I'd love to be able to say "any time this changes, call this method", or something like that. It could be useful for INotifyPropertyChanged, but also for other things as well.