xaml:
<Rectangle>
<Rectangle.RenderTransform>
<TranslateTransform x:Name="myTranslateTransform" />
</Rectangle.RenderTransform>
</Rectangle> cs:
myTranslateTransform.X = myTranslateTransform.X + 15;
myTranslateTransform.Y = myTranslateTransform.Y + 15;
http://msdn.microsoft.com/en-us/library/windows/apps/system.windows.media.translatetransform%28v=vs.105%29.aspx