If you observe WPF and Silverlight controls. Most of the controls in WPF are available in Silverlight4.
Take the layout controls as an example.
Layout controls are:
So here is the solution.
Go through this link
http://silverlight.codeplex.com/releases/view/43528
Close the Visual studio or Expression studio editors if they open that time. Then Save and run the msi installer.
Now you can see the Dock and wrap panel controls in your Silverlight control list like this:
So many new controls will add like this…
Hope it help you....