C#

using System;
using System.Runtime.InteropServices;

[
  GuidAttribute("4657278A-411B-11d2-839A-00C04FD918D0"),
  ClassInterface(ClassInterfaceType.None),
  ComImport
]
public class DragDropHelper : IDropTargetHelper, IDragSourceHelper
{
}

[
  GuidAttribute("4657278B-411B-11d2-839A-00C04FD918D0"),
  InterfaceType(ComInterfaceType.InterfaceIsIUnknown),
  ComImport
]
public interface IDropTargetHelper
{
}

[
  GuidAttribute("DE5BF786-477A-11d2-839D-00C04FD918D0"),
  InterfaceType(ComInterfaceType.InterfaceIsIUnknown),
  ComImport
]
public interface IDragSourceHelper
{
}

class Test
{
  static void Main()
  {
    DragDropHelper helper = new DragDropHelper();

    IDropTargetHelper dropHelper = (IDropTargetHelper)helper;
    IDragSourceHelper dragHelper = (IDragSourceHelper)helper;

    Console.WriteLine(dropHelper == null);
    Console.WriteLine(dragHelper == null);
  }
}

private void button_Click(object sender, EventArgs e)
{
    OtherWindow other = new OtherWindow();
    other.Show();
}

if(string == "something"){ }

string s = "Nick";
if(string.Compare(s, "Nick") == 0)
    {
    //...
    }