不能通过MVC3实体模型的数据注释声明非常规的PK

我试图为实体模型声明主键，最终将由ASP消耗。. NET MVC3创建一个控制器类，因此我用[Key]属性装饰一个值:

Foobar.cs

using System.ComponentModel.DataAnnotations;
public class Foobar
{
  [Key]
  public string Foo { get; set; }
  public string Bar { get; set; }
}

FoobarDbContext.cs

using System.Data.Entity;
public class FoobarDBContext : DbContext
{
  public DbSet<Foobar> Foobars { get; set; }
}

当尝试创建前面提到的Controller时，会导致以下错误:

---------------------------
Microsoft Visual Studio
---------------------------
Unable to retrieve metadata for 'Dotnet.Samples.AspNetMvc.Models.FoobarDBContext'.
One or more validation errors were detected during model generation:
- System.Data.Edm.EdmEntityType: : EntityType 'Foobar' has no key defined.
Define the key for this EntityType.
- System.Data.Edm.EdmEntityType: : EntityType 'FoobarDBContext' has no key defined.
Define the key for this EntityType.
- System.Data.Edm.EdmEntitySet: EntityType: EntitySet __Foobars__
is based on type ?Foo? that has no keys defined.
- System.Data.Edm.EdmEntitySet: EntityType: EntitySet __FoobarDBContexts__
is based on type __FoobarDBContext__ that has no keys defined.

---------------------------
OK   
---------------------------

任何建议都将非常感谢。提前感谢，

根据实体框架中的数据注释和代码优先

KeyAttribute用于指定a属性/列是主属性的一部分适用于实体的Key只有标量属性。

因此，我想我必须继续创建一个"非语义"标识符，如FoobarID，以利用代码生成功能。

[Key]
public string UserName { get; set; }