Why don't I see the += operator overloaded on System.Delegate?

Question

I see the equality comparison operators == and != overloaded on System.Delegate and MulticastDelegate but not the +

Answer 1

The C# compiler translates += operator to the call of the static method Delegate.Combine.

There are several cases when the compiler does such things, f.e. the + operator of the System.String is compiled to the String.Concat call. Therefore there isn't op_Add method in System.String.