void WindowOnActivated(object sender, WindowActivatedEventArgs windowActivatedEventArgs)
 {
     // If the TimePicker is in a TableView or ListView, when the application loses focus
     // the TextBlock/ComboBox controls (UWP and 8.1, respectively) which display its selected value
     // will go blank.
     // To fix this, we have to signal the renderer to invalidate if
     // Window.Activated occurs.
     ForceInvalidate?.Invoke(this, EventArgs.Empty);
 }
 void PickerOnDropDownClosed(object sender, object o)
 {
     // If the TimePicker is in a TableView or ListView and the user
     // opens one of the dropdowns but does not actually change the value,
     // when the dropdown closes, the selected value will go blank
     // To fix this, we have to invalidate the control
     // This only applies to Windows 8.1
     ForceInvalidate?.Invoke(this, EventArgs.Empty);
 }