FOREIGN_KEY约束异常

Question

我有一个带有ac＃code-behind的asp.net应用程序，连接到带有linq-to-entities的SQL数据库...当我尝试对以下代码'SaveChanges（）'时，我得到一个异常（列出下面）。什么是关于什么的想法？

private void setNewRide(long newRideID, int carNum)
        {
            handleCompletedRide(carNum);

            using (myEntities = new RamRideOpsEntities())
            {
                Vehicle assignedCar = myEntities.Vehicles.FirstOrDefault(car => car.CarNum == carNum);
                Ride newRide = myEntities.Rides.FirstOrDefault(ride => ride.identity == newRideID);

                if (assignedCar != null && newRide != null)
                {
                    vs_CurrentRideId = newRide.identity; //Save current ride to ViewState
                    vs_CarStatus = assignedCar.Status; //Save old status to ViewState

                    assignedCar.Status = "EnRoute";
                    assignedCar.CurrPassengers = newRide.NumPatrons;
                    assignedCar.StartAdd = newRide.PickupAddress;
                    assignedCar.EndAdd = newRide.DropoffAddress;
                    assignedCar.CurrentAdd = newRide.DropoffAddress;

                    assignedCar.Rides.Add(newRide);

                    newRide.TimeDispatched = DateTime.Now;
                    newRide.WaitTime = (((DateTime)newRide.TimeDispatched) - ((DateTime)newRide.TimeOfCall));
                    newRide.AssignedCar = carNum;
                    newRide.Status = "EnRoute";

                    myEntities.SaveChanges(); //EXCEPTION HERE!
                    SelectCarUP.DataBind();
                    SelectCarUP.Update();                    
                }
            }
        }

例外：

  

UPDATE语句与FOREIGN KEY约束冲突   \ “FK_Rides_Vehicles \”。冲突发生在数据库中   \“CWIS29RamRideOps \”，表\“dbo.Vehicles \”，列   '身份'。\ r \ n声明已被终止。

数据库：

Answer 1

这一行：

assignedCar.Rides.Add(newRide);

被翻译为SQL-INSERT - 虽然您已经有一个具有相同ID的记录。决定你想做什么：插入一个新的骑行（在这种情况下你应该对newRide的id进行NULL化），或者更新它（在这种情况下你应该只注释掉那行;更改将被保存）。

Answer 2

更改您的代码：

newRide.TimeDispatched = DateTime.Now;
newRide.WaitTime = (((DateTime)newRide.TimeDispatched) - ((DateTime)newRide.TimeOfCall));
newRide.AssignedCar = carNum;
newRide.Status = "EnRoute";

assignedCar.Status = "EnRoute";
assignedCar.CurrPassengers = newRide.NumPatrons;
assignedCar.StartAdd = newRide.PickupAddress;
assignedCar.EndAdd = newRide.DropoffAddress;
assignedCar.CurrentAdd = newRide.DropoffAddress;
assignedCar.Rides = newRide; // Your First Change here

myEntities.SaveChanges();