在迁移期间将标识设置为先前创建的列 [英] Set identity to the previous created column during migration

问题描述

我有一个带有CodeFirst数据库(实体框架6)和两个迁移步骤的项目. 通过使用Global.asax的Application_Start中的以下代码自动更新数据库:

I have a project with the CodeFirst database (Entity Framework 6) and two migration steps. Database is updated automatically by using this code in Application_Start in Global.asax:

Database.SetInitializer(
          new MigrateDatabaseToLatestVersion<MyDBEntities, MyNamespace.Configuration>());

第一个迁移步骤是创建表:

First migration step is creating the tables:

CreateTable(
     "dbo.GalleryAlbum",
      c => new
      {
           Id = c.Int(nullable: false),
           //other columns.....
       })
       .PrimaryKey(t => t.Id);

CreateTable(
       "dbo.GalleryPics",
       c => new
       {
           Id = c.Int(nullable: false),
           //other columns.....
       })
       .PrimaryKey(t => t.Id)
       .ForeignKey("dbo.GalleryAlbum", t => t.AlbumId)
       .Index(t => t.AlbumId);

第二个迁移步骤是将标识添加到已创建的表中

Second migration step is adding identities to the created tables:

AlterColumn("dbo.GalleryAlbum", "Id", c => c.Int(nullable: false, identity: true));
AlterColumn("dbo.GalleryPics", "Id", c => c.Int(nullable: false, identity: true));

运行该应用程序时，可以看到第二个迁移代码正在运行，有关两次迁移的信息已添加到_MigrationHistory表中，但两个表中的列均未更改(没有Identity).这是模式:

When I run the application, I can see that second migration code is running, information about two migrations is added to the _MigrationHistory table, but columns in both tables are not changed (without Identity). Here is the schema:

[Id]        INT             NOT NULL,
//other columns

首次迁移的代码优先类如下:

Code First classes for the first migration are the following:

 public partial class GalleryAlbum
 {
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int Id { get; set; }
 }
 //GalleryPics is the same

这是第二个迁移步骤:

public partial class GalleryAlbum
 {
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
 }
 //GalleryPics is the same

能否请您告诉我，为什么没有将身份添加到这些列中以及如何解决?

Could you please tell me, why Identity is not added to these columns and how I can fix it?

谢谢.

更新: 生成的对数据库的更新请求，这是我从IDbCommandInterceptor获得的:

Update: Generated update requests to the database, which I got from the IDbCommandInterceptor:

ALTER TABLE [dbo].[GalleryAlbum] ALTER COLUMN [Id] [int] NOT NULL
ALTER TABLE [dbo].[GalleryPics] ALTER COLUMN [Id] [int] NOT NULL

推荐答案

您不能在SQL Server中将列更改为Identity，请参见

You can't ALTER a column to Identity in SQL Server, see Adding an identity to an existing column

相反，请尝试一步添加标识和列:

Instead try add identity and column in one step:

CreateTable(
         "dbo.GalleryAlbum",
          c => new
          {
              Id = c.Int(nullable: false, identity:true),
              //other columns.....
          }).PrimaryKey(t => t.Id);

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