Question

我在使用EF 4.1 Code First时遇到了一个奇怪的问题，即使我已经配置了一个实体来为其继承的属性生成列，它仍然会加入到继承类型的表中。

以下是我的课程：

public class Human
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class SuperHuman : Human
{
    public int Id { get; set; }
    public string Powers { get; set; }
}


public class MarvelDbContext : DbContext
{
    public DbSet<Human> Humans { get; set; }
    public DbSet<SuperHuman> SuperHumans { get; set; }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<SuperHuman>().Map(m => m.MapInheritedProperties());
    }
}

以下是生成的查询：

    SELECT 
[Limit1].[C3] AS [C1], 
[Limit1].[C1] AS [C2], 
[Limit1].[C2] AS [C3], 
[Limit1].[C4] AS [C4]
FROM ( SELECT TOP (1) 
    [UnionAll1].[Id] AS [C1], 
    [UnionAll1].[Name] AS [C2], 
    CASE WHEN ([UnionAll1].[C2] = 1) THEN '0X' ELSE '0X0X' END AS [C3], 
    CASE WHEN ([UnionAll1].[C2] = 1) THEN CAST(NULL AS varchar(1)) ELSE [UnionAll1].[C1] END AS [C4]
    FROM  (SELECT 
        [Extent1].[Id] AS [Id], 
        [Extent1].[Name] AS [Name], 
        CAST(NULL AS varchar(1)) AS [C1], 
        cast(1 as bit) AS [C2]
        FROM [dbo].[Humen] AS [Extent1]
    UNION ALL
        SELECT 
        [Extent2].[Id] AS [Id], 
        [Extent2].[Name] AS [Name], 
        [Extent2].[Powers] AS [Powers], 
        cast(0 as bit) AS [C1]
        FROM [dbo].[SuperHumans] AS [Extent2]) AS [UnionAll1]
)  AS [Limit1]

我只想查询人类表。

Answer 1

这就是EF的表现方式。如果您查询Human设置，它始终会覆盖所有派生表，因为SuperHuman仍然是Human，因为SuperHuman的实例是人类查询的有效结果。

EF Code First：检索基类型查询所有派生类型表

1 个答案: