TextBox RaiseEvent KeyDownEvent does not work

Question

Trying to raiseEvent to textBox - but i don't see the key value in the textBox text. I can see that the textbox event "OnKeyDownEvent" is stopping in breakpoints - but i don't understand why the text of the KeyEventArgs ( Key.D0 ) is not insert into the textbox text.

The code:

 if( TextBoxInFocus != null ) 
{ 
    KeyEventArgs k = new KeyEventArgs( Keyboard.PrimaryDevice, Keyboard.PrimaryDevice.ActiveSource, System.Environment.ProcessorCount, Key.D0 ); 
    //KeyEventArgs k = new KeyEventArgs( Keyboard.PrimaryDevice, Keyboard.PrimaryDevice.ActiveSource, 0, Key.D0 ); 
    k.RoutedEvent = UIElement.KeyDownEvent; 
    TextBoxInFocus.RaiseEvent( k ); 
    k.RoutedEvent = UIElement.KeyUpEvent; 
    TextBoxInFocus.RaiseEvent( k ); 



}