c# - Linq to SQL 记录未更新

Question

我正在尝试从表中获取记录列表，然后在 foreach 中获取循环我正在尝试 update一份一份的记录。

这是我的代码

     public IEnumerable<MessageOut> GetSMSInformation()
        {
            using (var db = new DataClasses1DataContext())
            {
                var sms = db.MessageOuts.Where(msg => msg.msgstatus.Equals("Pending")).Select(msg => msg);
                return sms.ToList();
            }
        }



     public void StartSMSSending()
        {
            var information = GetSMSInformation();

            foreach (var sms in information)
            {
                SendSMS(sms.reciever, sms.msg);
                UpdateRecords(sms,"Delivered", DateTime.Now);
            }
        }

   public void UpdateRecords(MessageOut sms, string msgStatus, DateTime sentTime)
        {
            using (var db = new DataClasses1DataContext())
            {
                sms.msgstatus = msgStatus;
                sms.senttime = sentTime;
                db.SubmitChanges();
            }
        }

记录只是不更新​​。我也没有收到任何错误。

有人可以帮我解决这个问题吗？

Answer 1

为了使用 Linq2Sql 类执行更新操作，您需要保持上下文处于事件状态。在上面的示例中，您将您的选择包含在 using 语句中，因此您的记录被返回，然后上下文被转储。当您进行更新时，会有一个新的上下文，因此没有注册到对象的更改。一种方法是使上下文成为更全局的对象或将其作为参数传递。

public IEnumerable<MessageOut> GetSMSInformation(DataContext context)
{
    var sms = context.MessageOuts.Where(
        msg => msg.msgstatus.Equals("Pending")).Select(msg => msg);
    return sms.ToList();
}

public void StartSMSSending()
{
    using (var db = new DataClasses1DataContext())
    {
        var information = GetSMSInformation(db);

        foreach (var sms in information)
        {
            SendSMS(sms.reciever, sms.msg);
            UpdateRecords(sms,"Delivered", DateTime.Now, db);
        }
    }
}

public void UpdateRecords(MessageOut sms, string msgStatus, DateTime sentTime, DataContext context)
{
    sms.msgstatus = msgStatus;
    sms.senttime = sentTime;
    context.SubmitChanges();
}

或者，您可以这样做(我的首选方法):

public IEnumerable<MessageOut> GetSMSInformation()
{
    var sms = Context.MessageOuts.Where(
        msg => msg.msgstatus.Equals("Pending")).Select(msg => msg);
    return sms.ToList();
}

public void StartSMSSending()
{
    var information = GetSMSInformation(db);

    foreach (var sms in information)
    {
        SendSMS(sms.reciever, sms.msg);
        UpdateRecords(sms,"Delivered", DateTime.Now, db);
    }
}

public void UpdateRecords(MessageOut sms, string msgStatus, DateTime sentTime)
{
    sms.msgstatus = msgStatus;
    sms.senttime = sentTime;
    Context.SubmitChanges();
}

private DataClasses1DataContext _context = null;
public DataClasses1DataContextContext
{
    get
    {
        return _context ?? (_context = new DataClasses1DataContext());
    }
}