/// <summary>
 /// Provides a deterministic way to create the Main property.
 /// </summary>
 public static void CreateMain()
 {
     if (_main == null)
     {
         _main = new MainViewModel();
     }
 }
 /// <summary>
 /// Provides a deterministic way to delete the Main property.
 /// </summary>
 public static void ClearMain()
 {
     _main = null;
 }