为什么在我的实体框架中添加一个子元素，尝试插入一个新的父项？ [英] Why does adding a child element to my entity framework try and insert a new parent?

问题描述

我在WCF中有一个C＃REST服务，它位于SQL 2008的EF 4.2框架之上。有几个实体，但两个重要的是Trips和他们的孩子，PlacesOfInterest。

I have a C# REST Service in WCF that sits on top of an EF 4.2 framework on SQL 2008. There are a few entities, but the two that matter are Trips and their children, PlacesOfInterest.

这里是表：

-- Creating table 'Trips'
CREATE TABLE [dbo].[Trips] (
[Id] uniqueidentifier  NOT NULL,
[Name] nvarchar(max)  NOT NULL,
[ArrivalDate] datetime  NULL,
[DepartureDate] datetime  NULL,
[WhereTo] nvarchar(max)  NOT NULL,
[CreatedDate] datetime  NULL,
[UpdatedDate] datetime  NULL,
[Album] nvarchar(max)  NOT NULL,
[UserToken] nvarchar(max)  NOT NULL,
[WallPostId] nvarchar(max)  NOT NULL
);
GO

-- Creating table 'PlacesOfInterest'
CREATE TABLE [dbo].[PlacesOfInterest] (
[Id] uniqueidentifier  NOT NULL,
[PhoneNumber] nvarchar(max)  NOT NULL,
[SmallPicture] nvarchar(max)  NOT NULL,
[LargePicture] nvarchar(max)  NOT NULL,
[HostId] nvarchar(max)  NOT NULL,
[HostName] nvarchar(max)  NOT NULL,
[Address1] nvarchar(max)  NOT NULL,
[Address2] nvarchar(max)  NOT NULL,
[Address3] nvarchar(max)  NOT NULL,
[City] nvarchar(max)  NOT NULL,
[State] nvarchar(max)  NOT NULL,
[Zip] nvarchar(max)  NOT NULL,
[Latitude] bigint  NOT NULL,
[Longitude] bigint  NOT NULL,
[URL] nvarchar(max)  NOT NULL,
[MapUrl] nvarchar(max)  NOT NULL,
[Hours] nvarchar(max)  NOT NULL,
[Name] nvarchar(max)  NOT NULL,
[PageId] nvarchar(max)  NOT NULL,
[Trip_Id] uniqueidentifier  NOT NULL,
[Category_Id] int  NULL
);
GO

这是我的POCO模型。

Here are my POCO Models.

public class Trip
{
    public Guid Id { get; set; }
    public string Name { get; set; }
    public DateTime ArrivalDate { get; set; }
    public DateTime DepartureDate { get; set; }
    public string WhereTo { get; set; }
    public DateTime CreatedDate { get; set; }
    public DateTime UpdatedDate { get; set; }
    public string Album { get; set; }
    public List<PlaceOfInterest> PlacesOfInterest { get; set; }
    public List<Photo> Photos { get; set; }
    public string UserToken { get; set; }
    public string WallPostId { get; set; }
}

public class PlaceOfInterest
{
    public Guid Id { get; set; }
    public string Name { get; set; }
    public string PhoneNumber { get; set; }
    public string Address1 { get; set; }
    public string Address2 { get; set; }
    public string Address3 { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string Zip { get; set; }
    public long Latitude { get; set; }
    public long Longitude { get; set; }
    public string SmallPicture { get; set; }
    public string LargePicture { get; set; }
    public string HostId { get; set; }
    public string HostName { get; set; }
    public string URL { get; set; }
    public string MapUrl { get; set; }
    public string Hours { get; set; }
    public Category Category { get; set; }
    public List<Photo> Photos { get; set; }
    public List<Checkin> Checkins { get; set; }
    public List<PoiAttribute> PoiAttributes { get; set; }
    public Guid TripId { get; set; }
    public string PageId { get; set; }
    [IgnoreDataMember]
    public Trip Trip { get; set; }
}

当我添加一个新的PlaceOfInterest时，实体框架试图插入一个列表，我得到一个重复的键错误。

When I add a new PlaceOfInterest, the Entity Framework tries to insert a list, and I get a duplicate key error.

    public static Guid Create(string tripId, Model.PlaceOfInterest instance)
    {
        var context = new Model.POCOTripContext();
        var cleanPoi = new Model.PlaceOfInterest();
        cleanPoi.Id = Guid.NewGuid();
        cleanPoi.Address1 = instance.Address1;
        cleanPoi.Address2 = instance.Address2;
        cleanPoi.Address3 = instance.Address3;
        cleanPoi.City = instance.City;
        cleanPoi.HostId = instance.HostId;
        cleanPoi.HostName = instance.HostName;
        cleanPoi.Hours = instance.Hours;
        cleanPoi.LargePicture = instance.LargePicture;
        cleanPoi.Latitude = instance.Latitude;
        cleanPoi.Longitude = instance.Longitude;
        cleanPoi.MapUrl = instance.MapUrl;
        cleanPoi.Name = instance.Name;
        cleanPoi.PageId = instance.PageId;
        cleanPoi.PhoneNumber = instance.PhoneNumber;
        cleanPoi.SmallPicture = instance.PhoneNumber;
        cleanPoi.State = instance.State;
        cleanPoi.Trip = Library.Trip.Get(new Guid(tripId));
        cleanPoi.URL = instance.URL;
        cleanPoi.Zip = instance.Zip;
        context.PlacesOfInterest.AddObject(cleanPoi);
        context.SaveChanges();
        return cleanPoi.Id;
    }

我不想让它插入那行，我只是想更新数据库中的TripId列。我做错了什么？

I don't want it to insert that trip, I just want it to update the TripId column in the database. What am I doing wrong?

推荐答案

很可能这一行是问题：

cleanPoi.Trip = Library.Trip.Get(new Guid(tripId))

如果 Get 从DB加载旅程，那么它显然在另一个上下文中加载 context 。你应该使用相同的上下文。要写这个丑陋的东西，就像： Get（context，new Guid（tripId））然后使用注入的上下文。

If Get loads the trip from the DB then it is loading it obviously in another context than context. You should use the same context. To write it ugly, something like: Get(context, new Guid(tripId)) and then use that injected context.

如果 Get 只需创建一个旅程的实例（新旅行{... } ），您必须将其附加到上下文中：

If Get just creates an instance of Trip (new Trip { ... }), you must attach it to the context:

cleanPoi.Trip = Library.Trip.Get(new Guid(tripId))
context.Trips.Attach(cleanPoi.Trip);

但是你们都不需要，因为你显然有一个外键属性。那么这就够了：

But you all don't need that because you apparently have a foreign key property. Then this is enough:

cleanPoi.TripId = new Guid(tripId);

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