LINQ to SQL ERROR使用事务：违反PK约束无法在对象中插入重复键＆＃39;＆＃39;该语句已终止

Question

我在交易中使用LINQ to SQL时遇到了一个奇怪的问题。

重现此行为的步骤：

1. 插入一些记录
2. 修改现有记录
3. 执行SubmitChanges(System.Data.Linq.ConflictMode.ContinueOnConflict)之前，修改外部应用程序的上述记录（例如sqlserver管理工作室）
4. 现在SubmitChanges（System.Data.Linq.ConflictMode.ContinueOnConflict）引发冲突错误
5. 解决冲突
6. 做另一个SubmitChanges(System.Data.Linq.ConflictMode.FailOnFirstConflict)
7. 这里有错误：违反PRIMARY KEY约束 PK_EmployeeTerritories 。无法在对象 dbo.EmployeeTerritories 中插入重复键。该语句已被终止。

以下是重现此行为的c＃代码，此代码使用NORTHWIND数据库：

static void Main(string[] args)
{
    using (Northwnd db = new Northwnd())
    {
        //=======================================================================================
        // RESTORE PREVIOUS STATUS ==============================================================
        //=======================================================================================
        EmployeeTerritory exitEt = (from et in db.EmployeeTerritories where et.EmployeeID == 5 && et.TerritoryID == "85014" select et).FirstOrDefault();
        if (exitEt != null)
            db.EmployeeTerritories.DeleteOnSubmit(exitEt);
        var existingRegToReset = (from er in db.Regions where er.RegionID == 2 select er).First();
        existingRegToReset.RegionDescription = "Western";
        db.SubmitChanges(System.Data.Linq.ConflictMode.FailOnFirstConflict);
        //=======================================================================================
        // RESTORE PREVIOUS STATUS ==============================================================
        //=======================================================================================

        EmployeeTerritory newEt = new EmployeeTerritory();
        newEt.EmployeeID = 5;
        newEt.TerritoryID = "85014";
        db.EmployeeTerritories.InsertOnSubmit(newEt);

        Order newO = new Order();
        newO.CustomerID = "WHITC";
        newO.EmployeeID = 5;
        newO.OrderDate = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day); 
        newO.RequiredDate= new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day);
        newO.ShippedDate= new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day);
        newO.ShipVia = 1;
        newO.Freight = (Decimal)4.56;
        newO.ShipName = "White Clover Markets";
        newO.ShipAddress = "1029 - 12th Ave. S.";
        newO.ShipCity = "Seattle";
        newO.ShipRegion = "WA";
        newO.ShipPostalCode = "98124";
        newO.ShipCountry = "USA";
        db.Orders.InsertOnSubmit(newO);

        var existingReg = (from er in db.Regions where er.RegionID == 2 select er).First();
        existingReg.RegionDescription = "Western1";

        Console.WriteLine("Submit the following update on database using Management Studio:'Update dbo.Region Set RegionDescription='Western2' Where RegionID=2'");
        Console.ReadLine();
        ChangeSet cs;
        using (TransactionScope ts = new TransactionScope(TransactionScopeOption.Required, TimeSpan.FromSeconds(0)))
        {
            try
            {
                try
                {
                    cs = db.GetChangeSet();
                    db.SubmitChanges(System.Data.Linq.ConflictMode.ContinueOnConflict);
                }
                catch (ChangeConflictException e)
                {
                    Console.WriteLine(e.Message);
                    // Automerge database values for members that client
                    // has not modified.
                    foreach (ObjectChangeConflict occ in db.ChangeConflicts)
                        occ.Resolve(RefreshMode.KeepChanges);
                    cs = db.GetChangeSet();
                }
                // Submit succeeds on second try.
                db.SubmitChanges(ConflictMode.FailOnFirstConflict);
            }
            catch (Exception ex)
            {
                throw;
            }
        }
        cs = db.GetChangeSet();
    }
}

我们需要交易才能完成当前数据库之外的其他操作。

感谢您的帮助

的Fabio