SubmitChanges() 抛出内部服务器错误

public void RejectOrder(string rejectReason, int selectedNewOrderId)
    {
        SFNewOrder sfNewOrder = mdbDataContext.SFNewOrders.FirstOrDefault(x => x.ID == selectedNewOrderId && !x.IsRejected);
        if (sfNewOrder != null)
        {
            sfNewOrder.IsRejected = true;                              
        }
        SFReject sfReject = new SFReject();
        sfReject.SFNewOrderID = sfNewOrder.ID;
        sfReject.RejectReason = rejectReason;
        sfReject.RejectedDate = DateTime.Now;           
        sfReject.RejectedBy = 2;
        mdbDataContext.SFRejects.InsertOnSubmit(sfReject);
        mdbDataContext.SubmitChanges();
    }

在这里，我想更改SFNewOrder表中IsRejected属性并在SFReject表中插入新记录。但我正在得到

内部服务器错误

。上

mdbDataContext.submitchanges();

请帮忙...提前谢谢。

public void RejectOrder(string rejectReason, int selectedNewOrderId, User user)
{
    SFNewOrder sfNewOrder = mdbDataContext.SFNewOrders.FirstOrDefault(x => x.ID == selectedNewOrderId && !x.IsRejected);
    if (sfNewOrder != null)
    {
        sfNewOrder.IsRejected = true;                              
    }
    SFReject sfReject = new SFReject();
    sfReject.SFNewOrder = sfNewOrder; 
    sfReject.RejectReason = rejectReason;
    sfReject.RejectedDate = DateTime.Now;           
    sfReject.User= user;
    mdbDataContext.SFRejects.InsertOnSubmit(sfReject);
    mdbDataContext.SubmitChanges();
}