I'm not sure about this, but :
public void bindcombo()
{
LogicLayer.Roles r = new LogicLayer.Roles();
dbmodelDataContext ds = new dbmodelDataContext();@;
cmbusertype.ItemsSource = ds.tblRoles.DefaultView;
cmbusertype.DisplayMemberPath = "Role";
cmbusertype.SelectedValuePath = "RoleId";
}
may work...
Have fun,
Eduard