Linq异常

Linq错误.
//testDataContext test=new testDataContext ();
  // var query1 = from t in test .TeacherInfo select t.TeaBirth.Value.Year.ToString();
  // DropDownList1.DataSource = query1;
  // DropDownList1.DataBind();
错在哪里？

[解决办法]
var query1 = from t in test.TeacherInfo select t.TeaBirth;
foreach(string q in query1) 
{ 
ListItem item =new ListItem(); 
item.value = q.TeaBirth.Value.Year.ToString();
DropDownList1.Items.Add(item); 
}