using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        IEnumerable<User> users = new[] { new User() };

        foreach (IUser user in users.OfType<IUser>())

            user.Destroy();

    }

}

​

public class User : IUser

{

    void IUser.Destroy()

    {

        Console.WriteLine("Destroy is called");

    }

}

​

public interface IUser

{

    void Destroy();

}