Open delegates

Do you know what is open delegate? I was quite surprised when I knew this. They exists since .NET 2.0, but I suspect they were not documented in MSDN initially, so e.g. I have known this much later.

Links:
- An example
- Official documentation.

So what is open delegate? It is a delegate bound only to a method, but not to an instance, so you can use the same delegate to call the method it is bound to on many instances. That's it.

And few more notes:
- Open delegate invocation must take at least the same time as the underlying virtual or interface method invocation, since .NET can't use the same way of invocation as for the regular one (there is no single method call address to use). We didn't test this yet, but if we will, I publish the results here.
- An open delegate bound to virtual generic method must be the slowest one - by the same reason. Do you know why virtual generic methods are the slowest ones? My next post here will explain this.
- Btw, various ways of invocation in .NET are perfectly described here. The article covers i.e. regular, virtual, interface methods and delegates.