Mar*_*cci 144 entity-framework ef-code-first
我的数据库中有一个名为SEntries的表(参见下面的CREATE TABLE语句).它有一个主键,几个外键,没有什么特别之处.我的数据库中有许多类似于那个表,但由于某种原因,该表最终在EF代理类上有一个"Discriminator"列.
这是在C#中声明类的方式:
public class SEntry
{
public long SEntryId { get; set; }
public long OriginatorId { get; set; }
public DateTime DatePosted { get; set; }
public string Message { get; set; }
public byte DataEntrySource { get; set; }
public string SourceLink { get; set; }
public int SourceAppId { get; set; }
public int? LocationId { get; set; }
public long? ActivityId { get; set; }
public short OriginatorObjectTypeId { get; set; }
}
public class EMData : DbContext
{
public DbSet<SEntry> SEntries { get; set; }
...
}
当我尝试向该表添加新行时,我收到错误:
System.Data.SqlClient.SqlException: Invalid column name 'Discriminator'.
只有从其他类继承C#类时才会出现此问题,但SEntry不会从任何类继承(如上所示).
除此之外,当我将鼠标悬停在SEntries属性的EMData实例上时,一旦我在调试器上获得了工具提示,它就会显示:
base {System.Data.Entity.Infrastructure.DbQuery<EM.SEntry>} = {SELECT
[Extent1].[Discriminator] AS [Discriminator],
[Extent1].[SEntryId] AS [SEntryId],
[Extent1].[OriginatorId] AS [OriginatorId],
[Extent1].[DatePosted] AS [DatePosted],
[Extent1].[Message] AS [Message],
[Extent1].[DataEntrySource] AS [DataE...
有任何建议或想法可以解决这个问题的根源吗？我尝试重命名表,主键和其他一些东西,但没有任何作用.
SQL-表:
CREATE TABLE [dbo].[SEntries](
[SEntryId] [bigint] IDENTITY(1125899906842624,1) NOT NULL,
[OriginatorId] [bigint] NOT NULL,
[DatePosted] [datetime] NOT NULL,
[Message] [nvarchar](500) NOT NULL,
[DataEntrySource] [tinyint] NOT NULL,
[SourceLink] [nvarchar](100) NULL,
[SourceAppId] [int] NOT NULL,
[LocationId] [int] NULL,
[ActivityId] [bigint] NULL,
[OriginatorObjectTypeId] [smallint] NOT NULL,
CONSTRAINT [PK_SEntries] PRIMARY KEY CLUSTERED
(
[SEntryId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
ALTER TABLE [dbo].[SEntries] WITH CHECK ADD CONSTRAINT [FK_SEntries_ObjectTypes] FOREIGN KEY([OriginatorObjectTypeId])
REFERENCES [dbo].[ObjectTypes] ([ObjectTypeId])
GO
ALTER TABLE [dbo].[SEntries] CHECK CONSTRAINT [FK_SEntries_ObjectTypes]
GO
ALTER TABLE [dbo].[SEntries] WITH CHECK ADD CONSTRAINT [FK_SEntries_SourceApps] FOREIGN KEY([SourceAppId])
REFERENCES [dbo].[SourceApps] ([SourceAppId])
GO
ALTER TABLE [dbo].[SEntries] CHECK CONSTRAINT [FK_SEntries_SourceApps]
GO
Mar*_*cci 305
事实证明,Entity Framework将假定从映射到数据库中的表的POCO类继承的任何类都需要Discriminator列,即使派生类不会保存到DB.
解决方案非常简单,您只需要添加[NotMapped]为派生类的属性.
例:
class Person
{
public string Name { get; set; }
}
[NotMapped]
class PersonViewModel : Person
{
public bool UpdateProfile { get; set; }
}
现在,即使将Person类映射到数据库上的Person表,也不会创建"Discriminator"列,因为派生类具有[NotMapped].
作为附加提示,您可以使用[NotMapped]不希望映射到DB上的字段的属性.
Wal*_*osz 42
这是Fluent API语法.
http://blogs.msdn.com/b/adonet/archive/2010/12/06/ef-feature-ctp5-fluent-api-samples.aspx
class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string FullName {
get {
return this.FirstName + " " + this.LastName;
}
}
}
class PersonViewModel : Person
{
public bool UpdateProfile { get; set; }
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
// ignore a type that is not mapped to a database table
modelBuilder.Ignore<PersonViewModel>();
// ignore a property that is not mapped to a database column
modelBuilder.Entity<Person>()
.Ignore(p => p.FullName);
}
我刚刚遇到这个问题,我的问题是由两个实体同时System.ComponentModel.DataAnnotations.Schema.TableAttribute引用同一个表引起的.
例如:
[Table("foo")]
public class foo
{
// some stuff here
}
[Table("foo")]
public class fooExtended
{
// more stuff here
}
将第二个foo改为foo_extended固定这个,我现在使用Table Per Type(TPT)
Another scenario where this occurs is when you have a base class and one or more subclasses, where at least one of the subclasses introduce extra properties:
class Folder {
[key]
public string Id { get; set; }
public string Name { get; set; }
}
// Adds no props, but comes from a different view in the db to Folder:
class SomeKindOfFolder: Folder {
}
// Adds some props, but comes from a different view in the db to Folder:
class AnotherKindOfFolder: Folder {
public string FolderAttributes { get; set; }
}
If these are mapped in the DbContext like below, the "'Invalid column name 'Discriminator'" error occurs when any type based on Folder base type is accessed:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Folder>().ToTable("All_Folders");
modelBuilder.Entity<SomeKindOfFolder>().ToTable("Some_Kind_Of_Folders");
modelBuilder.Entity<AnotherKindOfFolder>().ToTable("Another_Kind_Of_Folders");
}
I found that to fix the issue, we extract the props of Folder to a base class (which is not mapped in OnModelCreating()) like so - OnModelCreating should be unchanged:
class FolderBase {
[key]
public string Id { get; set; }
public string Name { get; set; }
}
class Folder: FolderBase {
}
class SomeKindOfFolder: FolderBase {
}
class AnotherKindOfFolder: FolderBase {
public string FolderAttributes { get; set; }
}
This eliminates the issue, but I don't know why!
我遇到了类似的问题，条件不完全相同，然后我看到了这篇文章。希望它可以帮助某人。显然，我正在使用我的一个 EF 实体模型作为一种类型的基类，该类型未在我的 dbcontext 中指定为 db 集。为了解决这个问题，我必须创建一个基类，该基类具有两种类型共有的所有属性，并从这两种类型中的新基类继承。
例子：
//Bad Flow
//class defined in dbcontext as a dbset
public class Customer{
public int Id {get; set;}
public string Name {get; set;}
}
//class not defined in dbcontext as a dbset
public class DuplicateCustomer:Customer{
public object DuplicateId {get; set;}
}
//Good/Correct flow*
//Common base class
public class CustomerBase{
public int Id {get; set;}
public string Name {get; set;}
}
//entity model referenced in dbcontext as a dbset
public class Customer: CustomerBase{
}
//entity model not referenced in dbcontext as a dbset
public class DuplicateCustomer:CustomerBase{
public object DuplicateId {get; set;}
}