实体框架4仅代码错误“不支持每种类型的多个对象集”

问题描述

我有两个仅代码POCO使用EF4和最新的CTP，针对现有的遗留数据库运行。对PocoA运行LINQ查询工作，直到我将下面的属性添加到该对象，我试图添加一个关系。

  public虚拟PocoB pocoB {get;组; 
  

一旦我这样做，我开始收到以下错误：

不支持每种类型的多个对象集。对象设置PocoA_DbSet和PocoB_DbSet都可以包含类型为PocoA的实例。

所以我接下来认为我的问题是因为我没有定义关系，而这个遗留数据库在主键和外键上使用'fk / pk'前缀而不是'Id'后缀。所以我将以下数据注释添加到上面指定的虚拟方法中，行为没有变化：

  [RelatedTo（Property = PocoB，ForeignKey =fkPocoB）] 
  

我真的很失去需要什么

解决方案

如果您的DbContext类暴露了多个DbSet< T> T发生多于一次的属性。基本上，它无法弄清楚哪个DbSet的类型T的实例属于。

在代码中，错误可能如下所示：

  public class MyContex：DbContext {
 public DbSet< PocoA> PocoA {get;组; } 
 public DbSet< PocoA> PocoB {get;组; } ... 
  

哪个最后一行应该是DbSet< PocoB>而不是DbSet< PocoA>

TL; DR - 您复制粘贴了一个属性，而忘记更改类型参数在DbSet中。

I have two "Code Only" POCO's using EF4 and the latest CTP, running against an existing, legacy database. Running a LINQ query against PocoA worked until I added the property below to that object, I was trying to add a relationship.

public virtual PocoB pocoB { get; set; }

Once I did that, I started getting the following error:

Multiple object sets per type are not supported. The object sets 'PocoA_DbSet' and 'PocoB_DbSet' can both contain instances of type 'PocoA'.

So I next thought my problem was because I had not defined the relationship, and this legacy database was using a 'fk/pk' prefix instead of an 'Id' suffix on the primary and foreign keys. So I added the following data annotation to the virtual method specified above, with no change in behavior:

[RelatedTo(Property="PocoB", ForeignKey="fkPocoB")]

I'm really at a loss for what needs to be changed to make this work.

解决方案

This error occurs if your DbContext class exposes multiple DbSet<T> properties where T occurs more than once. Basically it can't figure out which DbSet an instance of type T belongs to.

In code, the error probably looked like this:

public class MyContex : DbContext {
    public DbSet<PocoA> PocoA { get; set; }
    public DbSet<PocoA> PocoB { get; set; } ...

where that final line should have been DbSet<PocoB> instead of DbSet<PocoA>

TL;DR - you copy-pasted a property and forgot to change the type parameter in the DbSet.

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