如何在实体框架中保存子关系实体 [英] How to save child relationship entities in the Entity Framework

问题描述

我有一个Entity Framework v1项目。我有两个实体（角色和权限），它们之间存在多对多的关系。我传递一个要保存的对象（通过WCF调用，我不会自己创建它），它在多对多关系中有新的条目。

我使用context.ApplyPropertyChanges更新新属性的记录。我知道这不会更新关系。我试图做一个 ChildCollection .Add（ relatedObject ）;或 ChildCollection .Attach（ relatedObject ）。

当我使用添加方法时，我收到错误that：该对象不能添加到ObjectStateManager，因为它已经有一个EntityKey。使用ObjectContext.Attach附加具有现有密钥的对象。

当我使用附加方法时，会收到以下错误：该对象无法添加到ObjectStateManager因为它已经有一个EntityKey。使用ObjectContext.Attach附加一个具有现有密钥的对象。

我感到很沮丧，我想我可以听到实体框架对我笑了。有没有人知道我如何解决这个问题？

  MyRole x =上下文.Roles.FirstOrDefault（a => a.RoleId == this.RoleId）; 
 
 context.ApplyPropertyChanges（Roles，this）; 
 foreach（MyPermission p in this.Permissions）
 {
 x.Permissions.Add（p）; 
 // ^或v 
 x.Permissions.Attach（p）; 
} 
 context.SaveChanges（）; 
  

谢谢。

解决方案

哇。在这个问题上连续20个小时之后，我开始讨厌实体框架。以下是目前正在工作的代码。我很乐意任何关于如何使其更加精简的建议。

我做了WCF服务的重做，这样只有一个数据上下文。感谢Craig。

然后我不得不将代码更改为以下内容：

  MyRole x = context.Roles.FirstOrDefault（a => a.RoleId == this.RoleId）; 
 
 if（x == null）//插入
 {
 MyApplication t = this.Application; 
 this.Application = null; 
 context.Attach（t）; 
 this.Application = t; 
} 
 else //更新
 {
 context.ApplyPropertyChanges（Roles，this）; 
 x.Permissions.Load（）; 
 
 IEnumerable&Guid。 oldPerms = x.Permissions.Select（y => y.PermissionId）; 
列表< MyPermission> newPerms = this.Permissions.Where（y =>！oldPerms.Contains（y.PermissionId））。ToList（）; 
 IEnumerable&Guid。 curPerms = this.Permissions.Select（y => y.PermissionId）; 
列表< MyPermission> deletedPerms = x.Permissions.Where（y =>！curPerms.Contains（y.PermissionId））。ToList（）; 
 
 // new 
 foreach（newPerms中的MyPermission p）
 {
 x.Permissions.Add（context.Permissions.First（z => z.PermissionId == p.PermissionId））; 
} 
 
 //删除
 foreach（deletePerms中的MyPermission p）
 {
 x.Permissions.Remove（context.Permissions.First（z = > z.PermissionId == p.PermissionId））; 
} 
} 
  

I have an Entity Framework v1 project. I have two entities (Roles and Permissions), which have a many-to-many relationship with each other. I pass in a object to be saved (through a WCF call, I do not create it from a context myself), which has new entries in the many-to-many relationship.

I use "context.ApplyPropertyChanges" to update the record with the new properties. I know that this does not update relationships though. I attempt to either do a ChildCollection.Add(relatedObject); or ChildCollection.Attach(relatedObject).

When I use the "Add" method, I get the error that: The object cannot be added to the ObjectStateManager because it already has an EntityKey. Use ObjectContext.Attach to attach an object that has an existing key.

When I use the "Attach" method, I get the error that: The object cannot be added to the ObjectStateManager because it already has an EntityKey. Use ObjectContext.Attach to attach an object that has an existing key.

I am getting quite frustrated, and I think I can hear the Entity Framework laughing at me.

Does anyone know how I can resolve this?

MyRole x = context.Roles.FirstOrDefault(a => a.RoleId == this.RoleId);

context.ApplyPropertyChanges("Roles", this);
foreach (MyPermission p in this.Permissions)
{
     x.Permissions.Add(p);
    //  ^ or v
     x.Permissions.Attach(p);
}
context.SaveChanges();

Thanks.

解决方案

Wow. After 20 or so straight hours on this problem, I'm starting to hate the Entity Framework. Here is the code that appears to be working currently. I would appreciate any advice on how to make this more streamlined.

I did rework the WCF service so that there is only the one data context. Thanks Craig.

Then I had to change the code to the following:

MyRole x = context.Roles.FirstOrDefault(a => a.RoleId == this.RoleId);

if (x == null) // inserting
{
    MyApplication t = this.Application;
    this.Application = null;
    context.Attach(t);
    this.Application = t;
}
else // updating
{
    context.ApplyPropertyChanges("Roles", this);
    x.Permissions.Load();

    IEnumerable<Guid> oldPerms = x.Permissions.Select(y => y.PermissionId);
    List<MyPermission> newPerms = this.Permissions.Where(y => !oldPerms.Contains(y.PermissionId)).ToList();
    IEnumerable<Guid> curPerms = this.Permissions.Select(y => y.PermissionId);
    List<MyPermission> deletedPerms = x.Permissions.Where(y => !curPerms.Contains(y.PermissionId)).ToList();

    // new 
    foreach (MyPermission p in newPerms)
    {
        x.Permissions.Add(context.Permissions.First(z => z.PermissionId == p.PermissionId));
    }

    // deleted
    foreach (MyPermission p in deletedPerms)
    {
        x.Permissions.Remove(context.Permissions.First(z => z.PermissionId == p.PermissionId));
    }
}

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