I would rewrite your query like this
var query2 = from STUDENT in EntityManager.Students
join SORDER in EntityManager.Sorders
on STUDENT.ID equals SORDER.SORDER_ID
select new
{
STUDENT.ID,
STUDENT.NAME,
STUDENT.ADDRESS,
SORDER.SORDER_ID,
SORDER.OCITY
};
then assign it like this
DataGrid.ItemsSource = query2.ToList();
Please try that and let me know.