//---------------------------------------------------------------------------------------------------------------
 public static T OnClose <T>(this T t, FlexiblePopUpCallback action) where T : FlexiblePopUp
 {
     if (t.IsNull())
     {
         return(t);
     }
     t.Callback = action;
     return(t);
 }
 //---------------------------------------------------------------------------------------------------------------
 /// <summary>
 /// Closess popup without invoking Callback
 /// </summary>
 public void Kill()
 {
     this.Callback = null;
     this.CloseSelf();
 }