Looks like you may have typed in "Canvas.left" instead of "Canvas.Left" (with an uppercase L) when you entered the code on page 33.
This is a good example of what the "Watch it!" box on page 32 is talking about:
C# code must be added exactly as you see it here.
It’s really easy to throw off your code. When you’re adding C# code to your program, the capitalization has to be exactly right, and make sure you get all of the parentheses, commas, and semicolons. If you miss one, your program won’t work!"