實體框架遷移更新數據庫成功，但未添加數據庫列

Question

我在帶有SQL Server 2008 R2的VS2012中使用實體框架。 我已啟用遷移，並且正在向我的數據庫類之一（即設計）中添加一個字符串字段（即DropboxUrl）。

// Design.cs

public class Design
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public Guid Id { get; set; }

        [StringLength(Constants.DESIGN_NAME_MAX_LENGTH)]
        public string Name { get; set; }

        [StringLength(Constants.DESIGN_DESC_MAX_LENGTH)]
        public string Description { get; set; }

        public ItemDate Dates { get; set; }

        public string DropboxUrl { get; set; } // Added this line
    }

// SedaContext.cs:

public class SedaContext : DbContext
    {
        public DbSet<Company> Companies { get; set; }

        public DbSet<Design> Designs { get; set; }
…
}


// Global.aspx
protected void Application_Start()
        {

            // Application initialize
            // https://stackoverflow.com/questions/3600175/the-model-backing-the-database-context-has-changed-since-the-database-was-crea

            Database.SetInitializer<SedaContext>(null);

在Package Manager控制台中，當我運行PM> update-database時，它抱怨數據庫中已經存在一個名為“ Companies”的對象。 “公司”是我試圖更新的現有數據庫中當前存在的表。

即。

PM> update-database -verbose
Using StartUp project 'UI'.
Using NuGet project 'UI'.
Specify the '-Verbose' flag to view the SQL statements being applied to the target database.
Target database is: 'SedaDev' (DataSource: ., Provider: System.Data.SqlClient, Origin: Configuration).
No pending explicit migrations.
Applying automatic migration: 201405311730564_AutomaticMigration.
CREATE TABLE [dbo].[Companies] (
    [Id] [uniqueidentifier] NOT NULL DEFAULT newsequentialid(),
    [Name] [nvarchar](max),
    [Description] [nvarchar](max),
    [Owner_UserId] [int],
    CONSTRAINT [PK_dbo.Companies] PRIMARY KEY ([Id])
)
System.Data.SqlClient.SqlException (0x80131904): There is already an object named 'Companies' in the database.
...
   at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration)
   at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String targetMigration)
   at System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.Run()
   at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
   at System.AppDomain.DoCallBack(CrossAppDomainDelegate callBackDelegate)
   at System.Data.Entity.Migrations.Design.ToolingFacade.Run(BaseRunner runner)
   at System.Data.Entity.Migrations.Design.ToolingFacade.Update(String targetMigration, Boolean force)
   at System.Data.Entity.Migrations.UpdateDatabaseCommand.<>c__DisplayClass2.<.ctor>b__0()
   at System.Data.Entity.Migrations.MigrationsDomainCommand.Execute(Action command)
ClientConnectionId:fa9e9e62-aba0-435f-9309-e9fc8fbe19d5

There is already an object named 'Companies' in the database.

嘗試1：搜尋此錯誤后，我遇到了以下解決方法： http : //christesene.com/entity-framework-4-3-code-first-with-automatic-migrations/

建議我先跑步

PM> Add-migration initial

Scaffolding migration 'initial'.
The Designer Code for this migration file includes a snapshot of your current Code First model. This snapshot is used to calculate the changes to your model when you scaffold the next migration. If you make additional changes to your model that you want to include in this migration, then you can re-scaffold it by running 'Add-Migration initial' again.

並刪除了Up / Down方法：

即。 我可以看到DropboxUrl是Up方法中的一個字段，但是我按照建議將其刪除。

public override void Up()
        {
/*
    CreateTable(
                "dbo.Companies",
                c => new
                    {
                        Id = c.Guid(nullable: false, identity: true),
                        Name = c.String(),
                        Description = c.String(),
                        Owner_UserId = c.Int(),
                    })
                .PrimaryKey(t => t.Id)
                .ForeignKey("dbo.UserProfiles", t => t.Owner_UserId)
                .Index(t => t.Owner_UserId);
...
  CreateTable(                "dbo.Designs",
                c => new
                    {
                        Id = c.Guid(nullable: false, identity: true),
                        Name = c.String(maxLength: 100),
                        Description = c.String(maxLength: 1000),
                        Dates_Create = c.DateTime(nullable: false),
                        Dates_LastUpdate = c.DateTime(nullable: false),
                        DropboxUrl = c.String(),
                        Project_Id = c.Guid(),
                    })
                .PrimaryKey(t => t.Id)
                .ForeignKey("dbo.Projects", t => t.Project_Id)
                .Index(t => t.Project_Id);
*/
        }

之后，我再次運行update-database，它似乎成功。

PM> update-database -verbose
Using StartUp project 'UI'.
Using NuGet project 'UI'.
Specify the '-Verbose' flag to view the SQL statements being applied to the target database.
Target database is: 'SedaDev' (DataSource: phobos.spxis.com, Provider: System.Data.SqlClient, Origin: Configuration).
Applying explicit migrations: [201406020449030_initial].
Applying explicit migration: 201406020449030_initial.
INSERT [dbo].[__MigrationHistory]([MigrationId], [ContextKey], [Model], [ProductVersion])

VALUES (N'201406020449030_initial', N'Delecs.Seda.DataAccess.Migrations.Configuration',  0x1F8B0800000000000400ED1DCB72DCB8F19EAAFCC3D49C92544523D9F166
...
7B7C117028FAD9D8632C54E5F87C13A0D36590D83B7A73FA9F8AD368F7FFE3F0347EA807B340100 , N'6.0.2-21211')
Running Seed method

問題1：更新后我的表未更改（即，代碼中存在的DropboxUrl列未添加到數據庫）。

問題2：而且我也無法使數據庫恢復到初始狀態：

即。

PM> update-database -TargetMigration $InitialDatabase
Specify the '-Verbose' flag to view the SQL statements being applied to the target database.
Reverting migrations: [201406020449030_initial].
Reverting automatic migration: 201406020449030_initial.
Automatic migration was not applied because it would result in data loss.
PM> update-database -TargetMigration $InitialDatabase -force
Specify the '-Verbose' flag to view the SQL statements being applied to the target database.
Reverting migrations: [201406020449030_initial].
Reverting automatic migration: 201406020449030_initial.
System.Data.SqlClient.SqlException (0x80131904): Could not drop object 'dbo.UserProfiles' because it is referenced by a FOREIGN KEY constraint.

嘗試2：添加遷移時，我還嘗試使用-IgnoreChanges標志： ASP.NET SimpleMembershipProvider的自動遷移

PM> Add-migration initial -IgnoreChanges
Re-scaffolding migration 'initial'.

PM> update-database -verbose

同樣，我看到了同樣的事情，更新數據庫成功了，但是數據庫列DropboxUrl沒有添加到Designs表中。 但是，如果我創建一個新數據庫，則DropboxUrl列將按預期方式顯示。

問題：在更新數據庫時，如何解決數據庫錯誤中已經存在名為“ Companies”的對象，並且仍然成功添加我的列的問題？ 看來這應該是可行的基本方案。

謝謝。

Answer 1

當您在遷移中注釋掉Up（）和Down（）方法時，您刪除了添加數據庫列的代碼。

您應該按以下方式更改Up（）和Down（）：

public override void Up() {
   AddColumn("Companies", "DropboxUrl", x => x.String());
}

public override void Down() {
    DropColumn("Companies", "DropboxUrl");
}

為了使Entity Framework將來能夠為您解決這個問題，您需要進行一次初始遷移，以使其了解在將屬性添加到代碼之前已經存在一個表。 例如Add-Migration -force -ignore.

然后，您添加該列並轉到Add-Migration AddedDropboxUrlColumn ，它將如我在新遷移中所描述的那樣生成Up（）和Down（）方法。