public void NumbuttonReceiver(string buttonName, string buttonTag)
 {
     if (buttonTag == "Perform")
     {
         converterManager.Perform();
     }
     if (buttonTag == "Operate")
     {
         converterManager.AddKey(" " + buttonName + " ");
     }
     if (buttonTag == "Delete")
     {
         converterManager.DelKey();
     }
     if (buttonTag == "Number")
     {
         converterManager.AddKey(buttonName);
     }
     BaseButtonReceiver(-1);
 }