What do I have to change to the following code so that the background is red, neither of the 2 ways I tried worked:
(source: deviantsart.com)
I recommend reading the following blog post about debugging data binding: http://beacosta.com/blog/?p=52
And for this concrete issue: If you look at the compiler warnings, you will notice that you property has been hiding the Window.Background property (or Control or whatever class the property defines).