Yesterday I talked about how to write C# code to animate multiple transforms of an object.  It appears, to my dismay, that at the current time you are unable to animate objects completely in C#.  There is a work around by creating a XAML storyboard and importing into a string using the XAMLReader object.  Here are a few sites that cover this technique.

Silverlight 1.1 Storyboards and Managed Code
Creating animations in code with Silverlight 1.1 (stand November 2007)
Ceating a Game Loop