Sending Key or simulation Key press

 if (e.Key == Key.Down)
        {
            e.Handled = true;
            KeyEventArgs eInsertBack = new KeyEventArgs(Keyboard.PrimaryDevice, 

 Keyboard.PrimaryDevice.ActiveSource, 0, Key.Tab);
            eInsertBack.RoutedEvent = UIElement.KeyDownEvent;
            InputManager.Current.ProcessInput(eInsertBack);
        }