EntityCollections设置一个EntityReference.EntityKey来填充集合

问题描述

对实体框架有麻烦我一直使用EntityKey填充EntityReferences，以免在添加实体引用时无需查询数据库。现在我想为协会（EntityCollection）做同样的事情，但我不知道从哪里开始。以下是我正在尝试做的细节

表

  CREATE TABLE [dbo]。[Foo]（
 [FooId] [int] IDENTITY（1,1）NOT NULL，
 [FooName] [nvarchar]（50）NOT NULL，
 ）
 CREATE TABLE [dbo]。[Bar]（
 [BarId] [int] IDENTITY（1,1）NOT NULL，
 [BarName] [nvarchar]（50）NOT NULL， 
 CONSTRAINT [PK_Bar] PRIMARY KEY CLUSTERED 
）
 CREATE TABLE [dbo]。[FooBar]（
 [FooId] [int] NOT NULL，
 [BarId] [int] NOT NULL，
 CONSTRAINT [PK_FooBar] PRIMARY KEY CLUSTERED 
）
 ALTER TABLE [dbo]。[FooBar] WITH CHECK ADD CONSTRAINT [FK_FooBar_Bar] FOREIGN KEY（[BarId]）
参考[dbo]。[Bar]（[BarId]）
 
 ALTER TABLE [dbo]。[FooBar] CHECK CONSTRAINT [FK_FooBar_Bar] 
 
 ALTER TABLE [dbo ] [FooBar] WITH CHECK ADD CONSTRAINT [FK_FooBar_Foo] FOREIGN KEY（[FooId]）
参考[dbo]。[Foo]（[FooId]）
 
 ALTER TABLE [dbo]。 [FooBar] CHECK CONSTRAINT [FK_FooBar_Foo] 
  

现在w母鸡我将这个映射到实体框架我得到2个实体（Foo和Bar）与多对多关系。

我想要做的是添加一个新的Foo实体5条关联
我有Bars的ID，但是我不想查询数据库以获取所有5个条。

这是可能吗？

例如：

  Foo myFoo = new Foo（）; 
 Foo.Name =Hello
 Foo.Bars = //现在我只想为EntityCollection添加一组EntityKey 
  

解决方案

只需附加：

  var bar = new Bar {Id = barId}; 
 Context.AttachTo（Bars，bar）; 
 myFoo.Bars.Add（bar）; 
 Context.SaveChanges（）; 
  

没有DB查询 bar / p>

重要提示：您必须在添加之前附加 bar 关系到 myFoo ，以便EF知道您不会尝试插入新的栏。

Having Trouble with Entity Framework. I have been populating EntityReferences with an EntityKey inorder to eliminate the need for querying the database ever time I add an Entity Reference. Now I want to do the same thing for an Association (EntityCollection) but im not sure where to start. below are the details of what I am trying to do

Tables

CREATE TABLE [dbo].[Foo](
 [FooId] [int] IDENTITY(1,1) NOT NULL,
 [FooName] [nvarchar](50) NOT NULL,
)
CREATE TABLE [dbo].[Bar](
 [BarId] [int] IDENTITY(1,1) NOT NULL,
 [BarName] [nvarchar](50) NOT NULL,
 CONSTRAINT [PK_Bar] PRIMARY KEY CLUSTERED 
)
CREATE TABLE [dbo].[FooBar](
 [FooId] [int] NOT NULL,
 [BarId] [int] NOT NULL,
 CONSTRAINT [PK_FooBar] PRIMARY KEY CLUSTERED 
)
ALTER TABLE [dbo].[FooBar]  WITH CHECK ADD  CONSTRAINT [FK_FooBar_Bar] FOREIGN KEY([BarId])
REFERENCES [dbo].[Bar] ([BarId])

ALTER TABLE [dbo].[FooBar] CHECK CONSTRAINT [FK_FooBar_Bar]

ALTER TABLE [dbo].[FooBar]  WITH CHECK ADD  CONSTRAINT [FK_FooBar_Foo] FOREIGN KEY([FooId])
REFERENCES [dbo].[Foo] ([FooId])

ALTER TABLE [dbo].[FooBar] CHECK CONSTRAINT [FK_FooBar_Foo]

Now when I map this to the entityFramework I get 2 entities (Foo and Bar) with a Many to Many Relationship.

What Im trying to do is add a new Foo entity with 5 Bars associatedI have the IDs of the Bars but I do not want to query the database to get all 5 bars. I would prefer to just set an entityKey.

Is this possible?

for example:

Foo myFoo = new Foo();
Foo.Name = "Hello"
Foo.Bars = // now I would like to just populate a set of EntityKeys for the EntityCollection

解决方案

Just attach a stub entity:

var bar = new Bar { Id = barId };
Context.AttachTo("Bars", bar);
myFoo.Bars.Add(bar);
Context.SaveChanges();

No DB query there for bar.

Important: You must attach bar before adding the relationship to myFoo, so that the EF knows you're not trying to insert a new Bar.

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