When is it valid to say a method group conversion has taken place?

Question

So i'm not really convinced when its safe to say that a method group conversion occured. We have this multicast delegate from a previous post:

public partial class MainPage : PhoneApplicationPage
{
public delegate void MyDelegate(int a, int b);
// Constructor
public MainPage()
{
    InitializeComponent();

    MyDelegate myDel = new MyDelegate(AddNumbers);
    myDel += new MyDelegate(MultiplyNumbers);
    myDel(10, 20);
}

public void AddNumbers(int x, int y)
{
    int sum = x + y;
    MessageBox.Show(sum.ToString());
}

public void MultiplyNumbers(int x, int y)
{
    int mul = x * y;
    MessageBox.Show(mul.ToString());
}
}

I say that a method group conversion only occurs when we have assigned a method thats overloaded, and at least one overload matches the delegate. In this case there is no method group conversion.

a fellow programmer says that if you don't think MyDelegate myDel = AddNumbers; (with names referring to the question) is a method group conversion, then what would it be then?

The C# Language Specification: An implicit conversion (§6.1) exists from a method group (§7.1) to a compatible delegate type. Given a delegate type D and an expression E that is classified as a method group, an implicit conversion exists from E to D if [...]

So wich point of view is correct?

Answer 1

I say that a method group conversion only occurs when we have assigned a method thats overloaded

Nope, there's no requirement of overloading (by multiple methods) for method group conversions.

Any time you've got just a method name, or a method name qualified with a target (e.g. MultiplyNumbers or foo.MultiplyNumbers), that's a method group. If you're converting that to a delegate instance, that's a method group conversion.

EDIT: The section of the spec which is causing problems is this, in 7.1:

A method group, which is a set of overloaded methods resulting from a member lookup (7.4).

That "set of overloaded methods" can be a set of size 1 - it's still a method group.

This is backed up by 7.6.5.1 (Method Invocations) - emphasis mine:

For a method invocation, the primary-expression of the invocation-expression must be a method group. The method group identifies the one method to invoke or the set of overloaded methods from which to choose a specific method to invoke.

That makes it clear that a method group with one element is a meaningful concept.

Answer 2

Method group conversion has nothing to do with overloads. Don't get confused by "method group". It doesn't mean that it has to be more than one.

Answer 3

You have assigned a method in which at least one overload matches the delegate - it just so happens there is only one overload. The point of the "conversion" is simply that the compiler can infer the new MyDelegate bit rather than you needing to explicitly construct it.