我有以下的（简称为清楚起见） - 一个枚举，与枚举的基类，和两个派生类设置枚举一个特定的值

I have the following (abbreviated for clarity) - an enum, a base class with that enum, and two derived classes that set the enum to a specific value.

public enum MyEnum
{ 
    Value1, Value2
}

public class MyBaseClass
{ 
    public MyEnum { get; protected set; }
}

public class DerivedOne: MyBaseClass
{
    public DerivedOne { MyEnum = MyEnum.Value1; } 
}

public class DerivedTwo: MyBaseClass
{
    public DerivedTwo { MyEnum = MyEnum.Value2; }
}

我想要做的，是有实体框架5 DerivedOne和DerivedTwo，之间自动区分与MyEnum价值为基础的鉴别。我应该能够做到这一点的，按照惯例，每MyEnum == MyEnum.Value1重新presents DerivedOne，并MyEnum == MyEnum.Value2重新presents DerivedTwo。

What I want to do, is have Entity Framework 5 automatically distinguish between DerivedOne and DerivedTwo, with a MyEnum value based discriminator. I should be able to do this as, by convention, every MyEnum == MyEnum.Value1 represents DerivedOne, and MyEnum == MyEnum.Value2 represents DerivedTwo.

我想这在我的DbContext：

I tried this in my DbContext:

public class MyDbContext : DbContext
{
    DbSet<MyBaseClass> MyBaseClass { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<MyBaseClass>()
                    .Map<DerivedOne>(m => m.Requires(x => x.MyEnum == MyEnum.Value1));

        base.OnModelCreating(modelBuilder);
    }
}

不过，这将引发以下InvalidOperationException异常：

However, this throws the following InvalidOperationException:

这位前pression'X =>（转换（x.MyEnum）== 0）不是一个有效的属性EX pression。这位前pression应该重新present一个属性（...）

The expression 'x => (Convert(x.MyEnum) == 0)' is not a valid property expression. The expression should represent a property (...)

编辑：我相信我有一个稍远一点使用这样的：

I believe I got a little farther using this:

modelBuilder.Entity<MyBaseClass>().Map<DerivedOne>(m => m.Requires("MyEnum")
                                  .HasValue((Int32)MyEnum.Value1));

现在我得到这个EntityCommandCompilationException：

Now I get this EntityCommandCompilationException:

在开始行（...）条件成员MyBaseClass.MyEnum'比'ISNULL =假'等条件映射碎片问题的映射。无论是去除MyBaseClass.MyEnum条件或映射中删除。

Problem in mapping fragments starting at line (...) Condition member 'MyBaseClass.MyEnum' with a condition other than 'IsNull=False' is mapped. Either remove the condition on MyBaseClass.MyEnum or remove it from the mapping.

我如何才能解决这个任何提示？谢谢！

Any hints on how I can solve this? Thanks!

推荐答案

据我所知，你不能这样做。做了明确的要求指定disciminator只是给它一个名称 - 不能将它连接到你的财产。

As far as I know you cannot do that. Doing the explicit Requires to specify the disciminator is only to give it a name - not to connect it to your property.

据我所知，都会导致该错误（后下），你描述。如果要指定鉴别它必须是'automatic'one（至少我从来没有成功地定义这种方式）

As far as I know that always results in that error (later) that you're describing. If you want to specify discriminator it has to be 'automatic'one (at least I never managed to define it that way)

但是，你并不需要真的。在枚举和鉴别是内置你回来的类型 - 基于鉴别值，EF / CF正在建设或者Base`或DerivedOne或DerivedTwo。

But you don't need that really. The 'enum' and discriminator is built into the type you get back - based on the discriminator values, EF/CF is constructing either 'Base` or 'DerivedOne' or DerivedTwo.

因此​​，为了实现你愿意，你可以做以下什么...

So to implement what you want you can do the following...

public class MyBaseClass
{
    [NotMapped()]
    public virtual MyEnum MyEnum { get { return MyEnum.Base; } }
}

public class DerivedOne: MyBaseClass
{
    public string OneProp { get; set; }
    public override MyEnum MyEnum { get { return MyEnum.One; } }
}

public class DerivedTwo: MyBaseClass
{
    public string TwoProp { get; set; }
    public override MyEnum MyEnum { get { return MyEnum.Two; } }
}

或者只是使用是代替（如果你的作品）...

Or just use is instead (if it works for you)...

if (entity is MyBaseClass) // instead of enum  

或查询的...

or Query by...

.OfType<MyBaseClass>();