I have created a window as follows:
Window myWindow = new Window();
How can I add a Vertical Scroll Bar to this Windows and make the Scroll Bar only visible if the Height isn't large enough to show all the elements.
You could add a ScrollViewer element to your window and put the necessary controls into the ScrollViewer control.
<ScrollViewer VerticalScrollBarVisibility="Auto">
...
</ScrollViewer>
Or if you want to code it in the code-behind file you could write
ScrollViewer viewer = new ScrollViewer();
viewer.VerticalScrollBarVisibility = ScrollBarVisibility.Auto;
// append scroll viewer to window