WPF: How to make empty TextBlock not to occupy space?

Question

Let\'s say that I have a simple layout such as this:

Answer 1

You want to set the visibility of the textbox to "Collapsed".

Visibility can be either:
Visible - Self explanatory
Hidden - Invisible but still takes up space
Collapsed - Invisible and takes up no space

Edit: You should probably set up a trigger, like so: