实体框架代码首先创建“鉴别器”柱 [英] Entity framework code first creates "discriminator" column

问题描述

我正在使用EF CF方法与MySQL的网站。
由于某种原因，EF在我的Post表中创建一个名为Discriminator的列，并包含VARCHARPost。

为什么这个列被创建？我可以做一些事情来避免它被创建吗？

解决方案

c c>在 表层次结构 继承方案。如果你有这样的模型...

  public abstract class BaseEntity 
 {
 public int Id {get;组; } 
 // ... 
} 
 
 public class发布：BaseEntity 
 {
 // ... 
} 
 
 public class OtherEntity：BaseEntity 
 {
 // ... 
} 
  

...并使模型的 BaseEntity 部分，例如添加一个 DbSet< BaseEntity> 到您的派生上下文中，Entity Framework将默认将该类层次结构映射到单个表中，但引入一个特殊列 - Discriminator 来区分存储在此表中的不同类型（ Post 或 OtherEntity ）。此列填充了类型的名称（再次 Post 或 OtherEntity ）。

I am using EF CF approach for a website with MySQL. For some reason EF creates a column in my Post table called "Discriminator" and contains the VARCHAR "Post".

Why is this column created? Can I do something to avoid it being created? Are there any advantages of having this column?

解决方案

The Discriminator column is used and required in Table-Per-Hierarchy inheritance scenarios. If you for example have a model like this ...

public abstract class BaseEntity
{
    public int Id { get; set; }
    //...
}

public class Post : BaseEntity
{
    //...
}

public class OtherEntity : BaseEntity
{
    //...
}

... and make the BaseEntity part of the model, for instance by adding a DbSet<BaseEntity> to your derived context, Entity Framework will map this class hierarchy by default into a single table, but introduce a special column - the Discriminator - to distinguish between the different types (Post or OtherEntity) stored in this table. This column gets populated with the name of the type (again Post or OtherEntity).

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