SaveChanges正在插入重复的内容

Question

我遇到了一个奇怪的问题，当使用嵌套的上下文实例多次调用SaveChanges()时（即使用using来创建上下文的实例），它会插入重复的内容，而不是更新它。

基本上，我正在嵌套两个上下文，将两行插入两个不同的表（使用两个不同的上下文），然后更新其中一行。

即。

插入表A 插入表B 使用表B中的值更新表A

在我更新表A时，它会根据需要成功更新行，但它也会插入一个重复的行（没有更新的值）。

有人能说清楚为什么会发生这种情况吗？

干杯

加文

编辑：道歉，我知道我应该发布一些代码来帮助，但我认为这可能会让人感到困惑。

public ActionResult Payment(int packageID, string action)
{
    int c = 0;
    using (PackageContext pc = new PackageContext())
    {
        Package selectedPackage = pc.Packages.Find(packageID);
        // store the user's package
        UserSubscriptionHistory sub;
        using (UserSubscriptionHistoryContext ushc = new UserSubscriptionHistoryContext())
        {
            sub = new UserSubscriptionHistory();
            sub.UserID = Core.CurrentUserID;
            sub.PackageID = packageID;
            sub.Duration = selectedPackage.Duration;
            sub.Cost = selectedPackage.Cost;
            ushc.History.Add(sub);
            c = ushc.SaveChanges(); // c returns 1 row changed, as one row is inserted

            if (c == 0)
            {
                throw new Exception("An unknown error occured");
            }
            // has the user selected a trial package?
            if (!selectedPackage.IsTrial.HasValue || !selectedPackage.IsTrial.Value)
            {
                // get me some money ;)
                Paypal pp = new Paypal();
                PaymentTransaction tran;
                using (PaymentTransactionContext ptc = new PaymentTransactionContext())
                {
                    tran = new PaymentTransaction();
                    tran.UserSubscriptionHistoryID = sub.UserSubscriptionHistoryID;
                    tran.UserID = Core.CurrentUserID;
                    tran.Description = "hidden";
                    tran.Amount = selectedPackage.Cost;
                    ptc.Transactions.Add(tran);
                    c = ptc.SaveChanges(); // c returns 1 row changed, as one row is inserted

                    if (c == 0)
                    {
                        throw new Exception("An unknown error occured");
                    }

                    sub.TransactionID = tran.PaymentTransactionID;
                    c = ushc.SaveChanges(); // c returns 2, as one row is updated, but the duplicate is inserted.

                    if (c == 0)
                    {
                        throw new Exception("An unknown error occured");
                    }

                    string success = Core.ResolveServerUrl(Url.Action("validate_payment", "User", new { accountAction = action }));
                    string cancelled = Core.ResolveServerUrl(Url.Action("cancelled", "User"));
                    string notification = Core.ResolveServerUrl(Url.Action("Process", "Payment"));

                    string token = pp.SetExpressCheckout(selectedPackage.Cost.ToString("#.##"), tran.Description, tran.PaymentTransactionID.ToString(), success, cancelled, notification, com.paypal.soap.api.PaymentActionCodeType.Sale, com.paypal.soap.api.CurrencyCodeType.GBP);
                    if (token != "Failure")
                    {
                        tran.VendorToken = token;
                        ptc.SaveChanges();
                        return Redirect(string.Format("https://www.{0}paypal.com/webscr?cmd=_express-checkout&token={1}", (PaypalConfiguration.Sandbox ? "sandbox." : ""), token));
                    }
                    else
                    {
                        ViewBag.Error = "Unable to take your payment, please contact us";
                    }
                }
            }
        }
    }
    Core.CurrentUser = null;
    return RedirectToActionPermanent("account", new { random = DateTime.Now.Ticks });
}

请在每次SaveChanges()来电后查看评论。

编辑2：我已经设法通过执行以下操作来解决此问题，尽管它看起来不像以前那样整洁：

public ActionResult Payment(int packageID, string action)
{
    int c = 0;
    using (PackageContext pc = new PackageContext())
    {
        Package selectedPackage = pc.Packages.Find(packageID);
        // store the user's package
        UserSubscriptionHistory sub;
        using (UserSubscriptionHistoryContext ushc = new UserSubscriptionHistoryContext())
        {
            sub = new UserSubscriptionHistory();
            sub.UserID = Core.CurrentUserID;
            sub.PackageID = packageID;
            sub.Duration = selectedPackage.Duration;
            sub.Cost = selectedPackage.Cost;
            ushc.History.Add(sub);
            c = ushc.SaveChanges();
        }

        if (c == 0)
        {
            throw new Exception("An unknown error occured");
        }
        // has the user selected a trial package?
        if (!selectedPackage.IsTrial.HasValue || !selectedPackage.IsTrial.Value)
        {
            // get me some money ;)
            Paypal pp = new Paypal();
            PaymentTransaction tran;
            using (PaymentTransactionContext ptc = new PaymentTransactionContext())
            {
                tran = new PaymentTransaction();
                tran.UserSubscriptionHistoryID = sub.UserSubscriptionHistoryID;
                tran.UserID = Core.CurrentUserID;
                tran.Description = "hidden";
                tran.Amount = selectedPackage.Cost;
                ptc.Transactions.Add(tran);
                c = ptc.SaveChanges();
            }

            if (c == 0)
            {
                throw new Exception("An unknown error occured");
            }

            using (UserSubscriptionHistoryContext ushc = new UserSubscriptionHistoryContext())
            {
                ushc.History.Attach(sub);
                sub.TransactionID = tran.PaymentTransactionID;
                c = ushc.SaveChanges();
            }

            if (c == 0)
            {
                throw new Exception("An unknown error occured");
            }

            string success = Core.ResolveServerUrl(Url.Action("validate_payment", "User", new { accountAction = action }));
            string cancelled = Core.ResolveServerUrl(Url.Action("cancelled", "User"));
            string notification = Core.ResolveServerUrl(Url.Action("Process", "Payment"));

            string token = pp.SetExpressCheckout(selectedPackage.Cost.ToString("#.##"), tran.Description, tran.PaymentTransactionID.ToString(), success, cancelled, notification, com.paypal.soap.api.PaymentActionCodeType.Sale, com.paypal.soap.api.CurrencyCodeType.GBP);
            if (token != "Failure")
            {
                using (PaymentTransactionContext ptc = new PaymentTransactionContext())
                {
                    ptc.Transactions.Attach(tran);
                    tran.VendorToken = token;
                    ptc.SaveChanges();
                }
                return Redirect(string.Format("https://www.{0}paypal.com/webscr?cmd=_express-checkout&token={1}", (PaypalConfiguration.Sandbox ? "sandbox." : ""), token));
            }
            else
            {
                ViewBag.Error = "Unable to take your payment, please contact us";
            }
        }
    }
    Core.CurrentUser = null;
    return RedirectToActionPermanent("account", new { random = DateTime.Now.Ticks });
}