Question

Other than doing this is there a better way to determine whether type is a one of the Action<> delegates.

if(obj is MulticastDelegate && obj.GetType().FullName.StartsWith("System.Action"))
{
   ...
}

Answer 1

This seems perfectly straightforward.

static bool IsAction(Type type)
{
    if (type == typeof(System.Action)) return true;
    Type generic = null;
    if (type.IsGenericTypeDefinition) generic = type;
    else if (type.IsGenericType) generic = type.GetGenericTypeDefinition();
    if (generic == null) return false;
    if (generic == typeof(System.Action<>)) return true;
    if (generic == typeof(System.Action<,>)) return true;
    ... and so on ...
    return false;
}

I’m curious as to why you want to know this though. What do you care if a particular type happens to be one of the versions of Action? What are you going to do with that information?