动作委托可以指向具有返回类型的方法吗？

Question

Can action delegates point to methods having a return type? For eg

Action a = () => Add();  
int Add()
{
  return 5 + 6;
}

The above code compiles. Now if I write the above something like

Action a = new Action(Add);

This does not compile. Could anyone please help me to understand the logic behind this?

Answer 1

Action a = () => Add();  
int Add()
{
  return 5 + 6;
}

is functionally equivalent to

Action a = ExecuteAdd;
int Add()
{
  return 5 + 6;
}
void ExecuteAdd() 
{
  Add();
}

And Action a = new Action(ExecuteAdd); would compile.

The reason being that () => Add(); actually creates an anonymous method . Assigning it to a variable of type Action infers the return type void .

Answer 2

First example creates an anonymous method that calls Add .

Action a = () => Add();
           ^        
Anonymous method with void return type.

If you want to assign method to Action you should do this:

Action a = Add;