One of my programming rules is that "just because you can do something, doesn't mean that you should". Take this piece of magic for example:
This is a lump of XAML, the code that you use to design the user interface for a Windows application. It tells the computer what the display will look like and defines display objects which link to the underlying code that provides the behaviours.
Except that it turns out that you can actually put code into your XAML, along with the display markup.
You should never do this. But I guess that knowing about it is cool. Find out more here.