C#

MessageBox.Show(Screen.PrimaryScreen.Bounds.Size.ToString());

public sealed class Singleton
{
  private static volatile WeakReference _Reference = new WeakReference(null);
  private static Object _Lock = new Object();
  <br>
  public static Singleton GetInstance()
  {
    // Get a strong reference to the singleton.
    // This may return null if the singleton was garbage collected.
    Singleton instance = _Reference.Target as Singleton;
    <br>
    // Use the double-checked locking pattern for performance.
    if (instance == null)
    {
      lock(_Lock)
      {
        instance = _Reference.Target as Singleton;
        if (instance == null)
        {
          instance = new Singleton();
          _Reference = new WeakReference(instance);
        }
      }
    }
    <br>
    return instance;
  }
}  // class