How to solve these problems with Asynchronous Callback?

I can't think of a clean solution to your problem. You'd have to write fugly code like this.

You should substitute the delegates with a consistent hierarchy with the common methods you need.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.