>This time you have to admit - this is just plain stupid!
>
>WTF is there no Visible property on a user control in WPF?????

Because they replaced it with something better :-}

>How do you hide a control in the code behind?

See the UIElement.Visibility property.
Vivsiblility.Hidden means it will not render but will occupy the same space.
Visibility.Collapsed frees up the space it would otherwise occupy so that it can be used by other controls.
Visibility.Visible means .........