Windows Phone 7.1 - How to change background image on button press?

How do I change the background image of some canvas from withing the c# code on button press? I know how to change the background color:

Canvas1.Background = new SolidColorBrush(Colors.Red);

I found a tutorial online , but VS says that "The type or namespace name 'BitmapImage' could not be found (are you missing a using directive or an assembly reference?)"

 var brush = new ImageBrush();
 brush.ImageSource开发者_开发百科 = new BitmapImage(new Uri(@"Images/myImage.png", UriKind.Relative));
 Canvas1.Background = brush;

What am I missing?

TIA!

You need to add a reference to the System.Windows.Media.Imaging namespace. Add this to the top of your class, where the other using directives are.

using System.Windows.Media.Imaging;