Covariance and Contravariance for Action Delegates

Question

I\'m stuck, why isn\'t this working:

  var childAction = new Action(blabla);
  Action upperAction = (Action

        

Answer 1

This is contravariance. This isn't working, because if this will be possible, you could write something like this:

interface IDomainCommand { }
class CancelCommand : IDomainCommand { }
class AcceptCommand : IDomainCommand { }

        Action a1 = c => { };
        Action a2 = a1;

        var acceptCommand = new AcceptCommand();

        a2(acceptCommand); // what???

a2 points to a1, and a1 can't accept AcceptCommand argument, because it is not a CancelCommand.