Xceed doesn't yet have a datagrid control for Silverlight. You can't use Xceed DataGrid for WPF with Silverlight, as that control was built to take full advantage of WPF.
We're developing a datagrid for Silverlight 3 and beyond, but it is quite some ways off before being available. Q1 2010 and the likes.
Odi
Odi Kosmatos
VP, R&D, Xceed