具有TPH和枚举的实体框架中的多个CASE WHEN

在EF 6.1.3上使用TPH时，我有一个非常奇怪的行为。下面是一个基本的复制示例：

public class BaseType
{
    public int Id { get; set; }
}
public class TypeA : BaseType
{
    public string PropA { get; set; }
}
public class TypeB : BaseType
{
    public decimal PropB { get; set; }
    public OneEnum PropEnum { get; set; }
}
public class TypeC : TypeB
{
    public int PropC { get; set; }
}
public enum OneEnum
{
    Foo,
    Bar
}
public partial class EnumTestContext : DbContext
{
    public EnumTestContext()
    {
        this.Database.Log = s => { Debug.WriteLine(s); };
    }
    public DbSet<BaseType> BaseTypes { get; set; }
}
class Program
{
    static void Main(string[] args)
    {
        Database.SetInitializer(new DropCreateDatabaseAlways<EnumTestContext>());
        using (var context = new EnumTestContext())
        {
            context.BaseTypes.Add(new TypeA() { Id = 1, PropA = "propA" });
            context.BaseTypes.Add(new TypeB() { Id = 2, PropB = 4.5M, /*PropEnum = OneEnum.Bar*/ });
            context.BaseTypes.Add(new TypeC() { Id = 3, PropB = 4.5M, /*PropEnum = OneEnum.Foo,*/ PropC = 123 });
            context.SaveChanges();
            var onetype = context.BaseTypes.Where(b => b.Id == 1).FirstOrDefault();
            Console.WriteLine("typeof {0} with {1}", onetype.GetType().Name, onetype.Id);
        }
        Console.WriteLine("Press any key to exit...");
        Console.ReadKey();
    }
}

这段代码运行得很好，但生成的查询非常奇怪和复杂，尤其是时有很多CASE

SELECT 
    [Limit1].[C1] AS [C1], 
    [Limit1].[Id] AS [Id], 
    [Limit1].[C2] AS [C2], 
    [Limit1].[C3] AS [C3], 
    [Limit1].[C4] AS [C4], 
    [Limit1].[C5] AS [C5]
    FROM ( SELECT TOP (1) 
        [Extent1].[Id] AS [Id], 
        CASE WHEN ([Extent1].[Discriminator] = N'BaseType') THEN '0X' WHEN ([Extent1].[Discriminator] = N'TypeA') THEN '0X0X' WHEN ([Extent1].[Discriminator] = N'TypeB') THEN '0X1X' ELSE '0X1X0X' END AS [C1], 
        CASE WHEN ([Extent1].[Discriminator] = N'BaseType') THEN CAST(NULL AS varchar(1)) WHEN ([Extent1].[Discriminator] = N'TypeA') THEN [Extent1].[PropA] WHEN ([Extent1].[Discriminator] = N'TypeB') THEN CAST(NULL AS varchar(1)) END AS [C2], 
        CASE WHEN ([Extent1].[Discriminator] = N'BaseType') THEN CAST(NULL AS decimal(18,2)) WHEN ([Extent1].[Discriminator] = N'TypeA') THEN CAST(NULL AS decimal(18,2)) WHEN ([Extent1].[Discriminator] = N'TypeB') THEN [Extent1].[PropB] ELSE [Extent1].[PropB] END AS [C3], 
        CASE WHEN ([Extent1].[Discriminator] = N'BaseType') THEN CAST(NULL AS int) WHEN ([Extent1].[Discriminator] = N'TypeA') THEN CAST(NULL AS int) WHEN ([Extent1].[Discriminator] = N'TypeB') THEN [Extent1].[PropEnum] ELSE [Extent1].[PropEnum] END AS [C4], 
        CASE WHEN ([Extent1].[Discriminator] = N'BaseType') THEN CAST(NULL AS int) WHEN ([Extent1].[Discriminator] = N'TypeA') THEN CAST(NULL AS int) WHEN ([Extent1].[Discriminator] = N'TypeB') THEN CAST(NULL AS int) ELSE [Extent1].[PropC] END AS [C5]
        FROM [dbo].[BaseTypes] AS [Extent1]
        WHERE ([Extent1].[Discriminator] IN (N'TypeA',N'TypeB',N'TypeC',N'BaseType')) AND (1 = [Extent1].[Id])
    )  AS [Limit1]

除了多个和无用的THEN CAST（NULL作为X）的成本外，在我的项目中，查询很大（>50 KB），因为我有很多派生类，包含很多属性。正如您所料，我的DBA团队不乐意看到对我们数据库的这种查询。

如果我删除TypeB上的枚举属性，那么请求会干净得多。如果我只有两个层次结构级别，也就是class TypeC : BaseType（与示例中的3相比，因为class TypeC : TypeB），也是一样的。

是否有任何设置、模型配置或解决方法来避免这种奇怪的行为？

更新

如果我删除TypeB.PropEnum ，这是生成的查询

SELECT TOP (1) 
    [Extent1].[Discriminator] AS [Discriminator], 
    [Extent1].[Id] AS [Id], 
    [Extent1].[PropA] AS [PropA], 
    [Extent1].[PropB] AS [PropB], 
    [Extent1].[PropC] AS [PropC]
    FROM [dbo].[BaseTypes] AS [Extent1]
    WHERE ([Extent1].[Discriminator] IN (N'TypeA',N'TypeB',N'TypeC',N'BaseType')) AND (1 = [Extent1].[Id])

更新2

一个常见的解决方案是创建一个单独的属性（整数值）并忽略enum属性。这是可行的，但有两个属性用于相同的目的是非常令人困惑的。

public class TypeB : BaseType
{
    public decimal PropB { get; set; }
    public int PropEnumValue { get; set; }
    [NotMapped]
    public OneEnum PropEnum
    {
        get { return (OneEnum)PropEnumValue; }
        set { PropEnumValue = (int)value; }
    }
}

更新3

我在codeplex上发现了一个错误：https://entityframework.codeplex.com/workitem/2117.这似乎还没有解决。