I have a function of this sort
void func(params object[] parameters) {
//Function Body
}
It can accept parameters of the following sort
func(10, "hello", 30.0);
func(10,20);
and so on.
I wanted to create an Action delegate for the above function. Is it possible? If not then why?
You can't use the existing Action delegates with params, but you can declare your own delegate that way:
public delegate void ParamsAction(params object[] arguments)
Then:
// Note that this doesn't have to have params, but it can do
public void Foo(object[] args)
{
// Whatever
}
...
ParamsAction action = Foo;
action("a", 10, 20, "b");
Of course you can create an Action<object[]> for your existing method - but you lose the params aspect of it, as that's not declared in Action<T>. So for example:
public static void Foo(params object[] x)
{
}
...
Action<object[]> func = Foo;
func("a", 10, 20, "b"); // Invalid
func(new object[] { "a", 10, 20, "b" }); // Valid
So if you're calling the delegate from code which wants to use params, you need a delegate type which includes that in the declaration (as per the first part). If you just want to create a delegate which accepts an object[], then you can create an instance of Action<object[]> using a method which has params in its signature - it's just a modifier, effectively.
This is where you run up against the limitations of functional programming in C#: you can not have a delegate with a variable number of generically-typed parameters (the Action delegates have a fixed number of generic parameters). But you may find it useful to create generic overloads for each number of parameters:
void func<T1>(T1 parameter1) { ... }
void func<T1,T2>(T1 parameter1, T2 parameter2) { ... }
void func<T1,T2,T3>(T1 parameter1, T2 parameter2, T3 parameter3) { ... }
What this gains you is the ability to pass those functions as parameters (ie, to pass them simply without using lambda expressions). So if you have a function like this:
void anotherFunc(Action<string, int> parameter) { ... }
Then you can call it like this:
anotherFunc(func);
you can not have a delegate with a variable number of parameters Sure you can.Action with a variable number of parameters.
Action delegate, which is what I was working off. Anyway, I've updated my answer to clarify my meaning.params object[]. The answer to that is simple, you can create a delegate that does that, just not an Action that does that.Action was arbitrary or mistaken. My answer is admittedly a bit orthogonal, but my hunch was that the OP needs to make use of the delegate in the way I suggested.