Question

I’m trying to check whether a given type is an action delegate, regardless of the amount of parameters.

The following code is the only way I know how to do this.

    public static bool IsActionDelegate( this Type source )
    {
        return source == typeof( Action ) ||
               source.IsOfGenericType( typeof( Action<> ) ) ||
               source.IsOfGenericType( typeof( Action<,> ) ) ||
               ....
               source.IsOfGenericType( typeof( Action<,,,,,,,,,,,,,,,> ) );
    }

IsOfGenericType() is another extension method of mine, which does what it says, it checks whether the type is of the given generic type.

Any better suggestions?

Answer 1

If you are just after the delegates that have a void return type you could do the following:

public static bool IsActionDelegate(Type sourceType)
{
    if(sourceType.IsSubclassOf(typeof(MulticastDelegate)) && 
       sourceType.GetMethod("Invoke").ReturnType == typeof(void))
        return true;
    return false;
}

This would not distinguish between Action and MethodInvoker (or other void delegates for that matter) though. As other answers suggest you could examine the type name, but that kinda smells 😉
It would help if you could clarify for what reason you want to identify Action delegates, to see which approach would work best.