c# - 将 DbSet 转换为 DbSet，其中 T 是 dbset 元素类型的接口(interface)

Question

我可以将我的 DbSet 从 DbSet 获取到 DbSet 吗？

  public IQueryable<T> GetData<T>() where T : class, IData
  { 
      var factory = EntityFrameworkConfiguration.TypeFactory[typeof(T)];
      var context = factory.Item2();         // context is a DbContext.
      var set = context.Set(factory.Item1);  //factory.Item1 is a Type object.
      return set.Cast<T>();

  }

factory.Item1是实现Iterface T的Class的类型

简单情况:

context.Set(typeof(MyClass));
how to return DbSet<IMyClass> ?  

更新

只需添加更多信息:

System.InvalidCastException:无法从非通用 DbSet 为“AzureStoreSubscriptionWrapper”类型的对象创建 DbSet。和代码:

[Title("AzureStoreSubscription"), DataScope("public"), KeyPropertyName("id_AzureStoreSubscriptionId"), ImmutableTypeId("{7a71540b-2eeb-32ae-a850-61c97e28df06}"), RelevantToUserType(UserType.Developer)]
public interface IAzureStoreSubscription : IData, IEntityFrameworkProvided
{
    // Properties
    [StoreFieldType(PhysicalStoreFieldType.DateTime), ImmutableFieldId("{35977476-f662-528b-8236-e993b65796a5}")]
    DateTime dt_ChangedTime { get; set; }
    [ImmutableFieldId("{cdc95aeb-a951-533c-87de-811fd4967ea6}"), StoreFieldType(PhysicalStoreFieldType.DateTime)]
    DateTime dt_CreatedTime { get; set; }
    [StoreFieldType(PhysicalStoreFieldType.String, 50), ImmutableFieldId("{83e0e743-0ec3-5f29-a4bd-14a1b97a13a8}")]
    DateTime? dt_DeletedTime { get; set; }
    [StoreFieldType(PhysicalStoreFieldType.Guid), ImmutableFieldId("{82f8da9f-00fa-5a00-b392-d47cb2d362d5}")]
    Guid id_AzureStoreSubscriptionId { get; set; }
    [ImmutableFieldId("{3bbef642-c88b-5a13-be89-65d537de3eb6}"), StoreFieldType(PhysicalStoreFieldType.Guid)]
    Guid id_TenantId { get; set; }
    [ImmutableFieldId("{273bd594-7aea-5ca0-b8da-4680a264bcfd}"), StoreFieldType(PhysicalStoreFieldType.String, 50)]
    string nvc_Email { get; set; }
    [StoreFieldType(PhysicalStoreFieldType.String, 50), ImmutableFieldId("{64d29805-d76a-55b0-a61a-abb76b5fd096}")]
    string nvc_EntityState { get; set; }
    [StoreFieldType(PhysicalStoreFieldType.String, 50), ImmutableFieldId("{a2172fef-de9a-559c-b33c-6c32d7f99727}")]
    string nvc_OptIn { get; set; }
    [ImmutableFieldId("{e1bb5d48-2d72-5ffc-b86f-f78216ea4ee4}"), StoreFieldType(PhysicalStoreFieldType.String, 50)]
    string nvc_RawData { get; set; }
    [ImmutableFieldId("{3e879595-9bbd-555f-8f63-f438e722915a}"), StoreFieldType(PhysicalStoreFieldType.String, 50)]
    string nvc_ResourceType { get; set; }
    [StoreFieldType(PhysicalStoreFieldType.String, 50), ImmutableFieldId("{67bd2cba-9c36-594c-8586-39c71974e572}")]
    string nvc_SubscriptionId { get; set; }
}




public class C1AzureStoreRPContext : DbContext
{
    // Methods
    public C1AzureStoreRPContext(string connectionstring);

    // Properties
    public DbSet<AzureStoreResourceWrapper> AzureStoreResource { get; set; }
    public DbSet<AzureStoreSubscriptionWrapper> AzureStoreSubscription { get; set; }
}




[Table("AzureStoreSubscriptions", Schema="cwac")]
public class AzureStoreSubscriptionWrapper : AzureStoreSubscription, IAzureStoreSubscription, IData, IEntityFrameworkProvided
{
    // Fields
    private DataSourceId _dataSourceId;

    // Methods
    public AzureStoreSubscriptionWrapper();

    // Properties
    [StoreFieldType(PhysicalStoreFieldType.DateTime), ImmutableFieldId("{35977476-f662-528b-8236-e993b65796a5}")]
    DateTime IAzureStoreSubscription.dt_ChangedTime { get; set; }
    [ImmutableFieldId("{cdc95aeb-a951-533c-87de-811fd4967ea6}"), StoreFieldType(PhysicalStoreFieldType.DateTime)]
    DateTime IAzureStoreSubscription.dt_CreatedTime { get; set; }
    [StoreFieldType(PhysicalStoreFieldType.String, 50), ImmutableFieldId("{83e0e743-0ec3-5f29-a4bd-14a1b97a13a8}")]
    DateTime? IAzureStoreSubscription.dt_DeletedTime { get; set; }
    [StoreFieldType(PhysicalStoreFieldType.Guid), ImmutableFieldId("{82f8da9f-00fa-5a00-b392-d47cb2d362d5}")]
    Guid IAzureStoreSubscription.id_AzureStoreSubscriptionId { get; set; }
    [ImmutableFieldId("{3bbef642-c88b-5a13-be89-65d537de3eb6}"), StoreFieldType(PhysicalStoreFieldType.Guid)]
    Guid IAzureStoreSubscription.id_TenantId { get; set; }
    [ImmutableFieldId("{273bd594-7aea-5ca0-b8da-4680a264bcfd}"), StoreFieldType(PhysicalStoreFieldType.String, 50)]
    string IAzureStoreSubscription.nvc_Email { get; set; }
    [StoreFieldType(PhysicalStoreFieldType.String, 50), ImmutableFieldId("{64d29805-d76a-55b0-a61a-abb76b5fd096}")]
    string IAzureStoreSubscription.nvc_EntityState { get; set; }
    [StoreFieldType(PhysicalStoreFieldType.String, 50), ImmutableFieldId("{a2172fef-de9a-559c-b33c-6c32d7f99727}")]
    string IAzureStoreSubscription.nvc_OptIn { get; set; }
    [ImmutableFieldId("{e1bb5d48-2d72-5ffc-b86f-f78216ea4ee4}"), StoreFieldType(PhysicalStoreFieldType.String, 50)]
    string IAzureStoreSubscription.nvc_RawData { get; set; }
    [ImmutableFieldId("{3e879595-9bbd-555f-8f63-f438e722915a}"), StoreFieldType(PhysicalStoreFieldType.String, 50)]
    string IAzureStoreSubscription.nvc_ResourceType { get; set; }
    [StoreFieldType(PhysicalStoreFieldType.String, 50), ImmutableFieldId("{67bd2cba-9c36-594c-8586-39c71974e572}")]
    string IAzureStoreSubscription.nvc_SubscriptionId { get; set; }
    public DataSourceId DataSourceId { get; }
}

Answer 1

能不能不要再在DbSet上运行Cast方法了？

http://msdn.microsoft.com/en-us/library/gg696369(v=vs.113).aspx

因此，如果以下是您的 DbSet:

var myClassSet = context.Set(typeof(MyClass));

你应该可以像这样转换它:

return myClassSet.Cast<IMyClass>();

它应该通过直接转换进行转换，因此转换为继承类时应该没有问题。如果这不起作用，请查看此链接:

http://social.msdn.microsoft.com/Forums/en-US/bb2ba471-7a19-4886-854b-eb5c7ebfcf74/dbsett-and-casting?forum=csharplanguage

希望对您有所帮助。