MVC3循环添加数据

 foreach (var item in orderdetails)
 {
  var billdetails = new BillDetail(){BillCode = billoflading.BillCode,StockId = item.StockId,PCS = item.PCS,CreateDate = DateTime.Now};
  _db.BillDetails.Add(billdetails);
 }            
 _db.SaveChanges();