title: Change rectangle background on mouse hover
body: <p>So I have a rectangle with no background and I want to give it a background gradient when the user hovers their mouse over it, and then remove the gradient when the mouse leaves the rectangle.</p>
  
  <p>Please can someone post the code that is needed for this, and tell me where to put it in the .cs/xaml file?</p>
  
  <p>Thanks.</p>