C#

[StructLayout(LayoutKind.Sequential)]
 public struct POINT
 {
   public int x;
   public int y;
 }
 [StructLayout(LayoutKind.Sequential)]
 public struct MSG
  {
     public IntPtr hwnd;
     public uint message;
     public IntPtr wParam;
     public IntPtr lParam;
     public int time;
     POINT pt;
  };

public class RenderLoop
{
  

  [DllImport("user32.dll")]
  public static extern bool PeekMessage( out MSG msg, IntPtr hwnd, uint wMsgFilterIn, uint wMsgFilterOut, uint wRemoveMsg );
  public RenderLoop()
  {
    Application.Idle += new EventHandler( this.Application_Idle );
  }
  private bool AppStillIdle
  {
      MSG msg;
   
      return (!PeekMessage( out msg, IntPtr.Zero, 0, 0, 0 ) );
  }

  public void Application_Idle( object sender, EventArgs e )
  {
      while( AppStillIdle )
      {
          RenderFrame();
      }
  }
}

struct Test
{
  int iCount;
}
class TestWrapper
{
  public Test test;
  public TestWrapper(Test test) { this.test = test;}
}

class Add : Form
{
   public Add(TestWrapper t)
   {
     t.test.iCount = 2;
   }
}

static void Main()
{
   TestWrapper w = new TestWrapper(new Test());
   Add a = new Add(w);
   Console.WriteLine(w.test.iCount);
}