DOES NOT WORK, GENERATED IL DOES NOT CONTAIN THE EXPECTED CALL. An exploration on how a mock framework can get a call to a method without specifying the arguments and then mock the real call. The C# compiler make it hard as method groups can't appear anywhere in the language. Well except in one place it seem...

ReferenceMethodGroup.cs

void Main()
{   
    IFoo foo = new Foo();
    A.CallMethodWithAnyArgs(() => A.Hack(__arglist(foo.Bar)));
}

public static class A
{
    public static void CallMethodWithAnyArgs(Action callSpecification)
    {
        // Can't use the expression version as expression trees can't contain arglist calls, but the IL of "callSpecification"
        // is available and can be disasembled to try to find the call...
        // (It's invalid and would throw BadImageFormatException if executed but it is still readable)
        
        callSpecification.Method.Disassemble().Dump();
        
        // The disasm doesn't show any reference to foo.Bar, did the compiler generate nothing
        // or is it just the disasm that can't interpret it ?
        //
        // IL_0000:  call        UserQuery+A.Hack
        // IL_0005:  nop         
        // IL_0006:  ret                 
        
        // Manual disasm
        var body = callSpecification.Method.GetMethodBody();
        var ilBytes = body.GetILAsByteArray();
        string.Join(" ", ilBytes.Select(b => b.ToString("X2"))).Dump();
        
        if ((ilBytes[0] != (byte)OpCodes.Call.Value) && (ilBytes[0] != (byte)OpCodes.Callvirt.Value))
        {
            throw new Exception("Not a method call");
        }
        int token = BitConverter.ToInt32(ilBytes, 1);
        var field = callSpecification.Method.Module.ResolveMethod(token);
        
        field.Dump();
        
        // Sadly it only contains a call to A.Hack, no trace of foo.Bar :-(
        // Compiler bug, but useless compiler bug...
    }
    
    public static void Hack(__arglist)
    {
        // Marker method
    }
}

interface IFoo
{
    int Bar(int i);
    bool Bar(float f);
}

class Foo : IFoo
{
    public int Bar(int i)
    {
        return 0;
    }
    
    public bool Bar(float f)
    {
        return false;
    }
}