Generic constraint: Enforce type to have static fu

问题:

I know you can write:

class GenericClass<T> where T : new()
{ 

}

to enforce that T has an empty constructor.

My Qs are :

1. can you enforce that T has a constructor with a specific type of parameter? Like:

   class SingletonFactoryWithEmptyConstructor<T> where T : new(int)
   

2. can you enforce that T has a static function (let's say, void F()) so that you can use this function inside the generic class? Like :

   class GenericClass<T> where T : void F()
   { 
      void G ()
      {
          T.F();
      }
   }
   

   I know you can specify that T implements an interface but I don't want that. I want to specify that T has a static function.

回答1:

No, there's nothing like this in C#.

I've previously suggested that "static interfaces" could express this reasonably neatly. They'd only be useful for generic type constraints (I suspect, anyway) but then you could express:

• Constructors with arbitrary parameters
• Static methods and properties
• Operators

The last of these points is particularly interesting in my view, allowing things like a generic "Average" method over numeric types with suitable addition and division operators.

I believe some folks at MS have thought about something similar, but I haven't heard anything to suggest they're actively working on it.