Question

I have a method declared on an interface like so:

public interface IInterface
{
    void DoSomething(string format, params object[] arguments);
}

I am dynamically loading a managed c++ class that uses an implementation of this interface. The interface and inmplementation are both C#.

IInterface^ foo = gcnew Implentation();

This call is fine:

foo->DoSomething("string", someParam);

This call fails:

foo->DoSomething("string");

It looks like if there are no parameters to pass it just can’t resolve the method which should accept any number of params (including zero of course). I could probably use a nullptr as a placeholder but that’s pretty ugly or I could add a superfluous overload of DoSomething(string format) which isn’t great either but better than making all calls more awkward than they should be.

Am I missing something or is this not supported? All the helpers on the internet show how to declare the params equivalent in c++ but that doesn’t help in my scenario.

Answer 1

I can’t replicate your problem.

Given the C# interface & implementation:

using System;

namespace SomeNamespace
{
    public interface IInterface
    {
        void Print(string format, params object[] args);
    }

    public class Implementation : IInterface
    {
        public void Print(string format, params object[] args)
        {
            Console.WriteLine(format, args);
        }
    }
}

This C++/CLI code works fine:

using namespace System;
using namespace SomeNamespace;

public ref class Test
{
public:
    static void Run()
    {
        IInterface^ foo = gcnew Implementation();
        foo->Print("hello, {0}", "world");
        foo->Print("hello, world");
    }
};

Is there another element that is missing here? Or have I missed the point 🙂