Action same as Func<TResult>?

Question

I came across a situation where i need some knowledge.

Below is the code:

// A function to match the delegate
public static int DoSomething()
{
   Console.WriteLine("i am called");
   return 1;
}

// Usage
Action action = () => DoSomething();
Func<int> func = () => DoSomething();
action();
func();

My understanding of Action used to be that it should match a delegate that accepts no parameter and returns nothing.

And for Func<int> that it should match a delegate that accepts no parameter and returns an int.

DoSomething method returns an integer, hence my question: () => DoSomething() is a delegate that returns an int. Func works as expected, but Action doesn't. Why? What am i failing to understand here?

The code compiles and runs properly, both output i am called. What i want to know is that why Action action = () => DoSomething(); is not a compile time error?

Answer 1

What i want to know is that why Action action = () => DoSomething(); is not a compile time error?

It compiles because you've got a lambda expression that calls the method but ignores the result. You couldn't use a method group conversion, e.g.

// Compile-time failure
// error CS0407: 'int Test.DoSomething()' has the wrong return type
Action action = DoSomething; 

(The same method group conversion for Func<Action, int> is fine.)

But instead, you're doing something more like this:

Action action = DoSomethingAndIgnoreResult;
...
private static void DoSomethingAndIgnoreResult()
{
    DoSomething(); // Hey, I'm ignoring the result. That's fine...
}