c# - Is there a way to distingish myFunc(1, 2, 3) from myFunc(new int[] { 1, 2, 3 })?

Question

A question to all of you C# wizards. I have a method, call it myFunc, and it takes variable length/type argument lists. The argument signature of myFunc itself is myFunc(params object[] args) and I use reflection on the lists (think of this a bit like printf, for example).

I want to treat myFunc(1, 2, 3) differently from myFunc(new int[] { 1, 2, 3 }). That is, within the body of myFunc, I would like to enumerate the types of my arguments, and would like to end up with { int, int, int} rather than int[]. Right now I get the latter: in effect, I can't distinguish the two cases, and they both come in as int[].

I had wished the former would show up as obs[].Length=3, with obs[0]=1, etc.

And I had expected the latter to show up as obs[].Length=1, with obs[0]={ int[3] }

Can this be done, or am I asking the impossible?

Answer 1

Well this will do it:

using System;

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("First call");
        Foo(1, 2, 3);
        Console.WriteLine("Second call");
        Foo(new int[] { 1, 2, 3 });
    }

    static void Foo(params object[] values)
    {
        foreach (object x in values)
        {
            Console.WriteLine(x.GetType().Name);
        }
    }
}

Alternatively, if you use DynamicObject you can use dynamic typing to achieve a similar result:

using System;
using System.Dynamic;

class Program
{
    static void Main(string[] args)
    {
        dynamic d = new ArgumentDumper();
        Console.WriteLine("First call");
        d.Foo(1, 2, 3);
        Console.WriteLine("Second call");
        d.Bar(new int[] { 1, 2, 3 });
    }
}

class ArgumentDumper : DynamicObject
{
    public override bool TryInvokeMember
        (InvokeMemberBinder binder,
         Object[] args,
         out Object result)
    {
        result = null;
        foreach (object x in args)
        {
            Console.WriteLine(x.GetType().Name);
        }
        return true;
    }
}

Output of both programs:

First call
Int32
Int32
Int32
Second call
Int32[]

Now given the output above, it's not clear where your question has really come from... although if you'd given Foo("1", "2", "3") vs Foo(new string[] { "1", "2", "3" }) then that would be a different matter - because string[] is compatible with object[], but int[] isn't. If that's the real situation which has been giving you problems, then look at the dynamic version - which will work in both cases.