Entity framework 意外删除了表，如何在不影响其它表的情况下恢复回来 (EF数据库迁移原理)...-白红宇

Entity framework 意外删除了表，如何在不影响其它表的情况下恢复回来 (EF数据库迁移原理)...

阅读量：6114 次

发布时间：2019-06-21

本文共 14528 字，大约阅读时间需要 48 分钟。

关于EntityFramework数据迁移原理

查询数据库的表"__MigrationHistory"，遍历代码库的Migrations文件夹下的所有文件，如果文件不在__MigrationHistory表内，那么就执行迁移。

有了上面的原理之后，我们来看一下如果我们不小心手动删除了一个表，如何在不影响其它表的情况下来恢复你删除的表：

方法一：

关于Model 以及 DBContext如下：

1  public class Blog 2     { 3         public int BlogId { get; set; } 4         public string Name { get; set; } 5  6         public string Url { get; set; } 7         public virtual List
     
       Posts { get; set; } 8     } 9 10     public class User11     {12         [Key]13         public int UserId { get; set; }14         public string Username { get; set; }15         public string DisplayName { get; set; }16         //public int? age { get; set; }17         //public string interest { get; set; }18     }19 20     public class School21     {22         public int SchoolId { get; set; }23 24         public string SchoolName { get; set; }25 26         public int SchoolLevel { get; set; }27     }28 29 30     public class Teacher31     {32         [Key]33         public int TecherId { get; set; }34         public string TeacherName { get; set; }35     }36 37 38     public class Post39     {40         public int PostId { get; set; }41         public string Title { get; set; }42         public string Content { get; set; }43 44         public int BlogId { get; set; }45         public virtual Blog Blog { get; set; }46     }47 48     public class Tutorial49     {50         [Key]51         public int Id { get; set; }52 53         public int Name { get; set; }54     }55 56     public class BloggingContext : DbContext57     {58         public DbSet
      
        Blogs { get; set; }59         public DbSet
       
         Posts { get; set; }60 61         public DbSet
        
          Users { get; set; }62 63         public DbSet
         
           Tutorials { get; set; }64         public DbSet
          
            Schools { get; set; }65 66 public DbSet
           
             Teachers { get; set; }67 protected override void OnModelCreating(DbModelBuilder modelBuilder)68 {69 modelBuilder.Entity
            
             ().Property(u => u.DisplayName).HasColumnName("display_name");70 modelBuilder.Entity
             
              ().Property(u => u.Username).HasColumnName("user_name");71 }72 }

migrations 文件夹下的文件如下：

对应数据库中的记录为：

假如此时我们手动删除了schools表，此时我们应该找到schools表的创建与修改的迁移code是在哪个Migrations文件夹下面的哪个文件，找到对应的文件

我们这里是在201503190341085_addmodels.cs中，

1   public partial class addmodels : DbMigration 2     { 3         public override void Up() 4         { 5             CreateTable( 6                 "dbo.Blogs", 7                 c => new 8                     { 9                         BlogId = c.Int(nullable: false, identity: true),10                         Name = c.String(),11                         Url = c.String(),12                     })13                 .PrimaryKey(t => t.BlogId);14 15             CreateTable(16                 "dbo.Posts",17                 c => new18                     {19                         PostId = c.Int(nullable: false, identity: true),20                         Title = c.String(),21                         Content = c.String(),22                         BlogId = c.Int(nullable: false),23                     })24                 .PrimaryKey(t => t.PostId)25                 .ForeignKey("dbo.Blogs", t => t.BlogId, cascadeDelete: true)26                 .Index(t => t.BlogId);27             28             CreateTable(29                 "dbo.Schools",30                 c => new31                     {32                         SchoolId = c.Int(nullable: false, identity: true),33                         SchoolName = c.String(),34                         SchoolLevel = c.Int(nullable: false),35                     })36                 .PrimaryKey(t => t.SchoolId);37 38             CreateTable(39                 "dbo.Tutorials",40                 c => new41                     {42                         Id = c.Int(nullable: false, identity: true),43                         Name = c.Int(nullable: false),44                     })45                 .PrimaryKey(t => t.Id);46 47             CreateTable(48                 "dbo.Users",49                 c => new50                     {51                         UserId = c.Int(nullable: false, identity: true),52                         user_name = c.String(),53                         display_name = c.String(),54                     })55                 .PrimaryKey(t => t.UserId);56             57         }58         59         public override void Down()60         {61             DropForeignKey("dbo.Posts", "BlogId", "dbo.Blogs");62             DropIndex("dbo.Posts", new[] { "BlogId" });63             DropTable("dbo.Users");64             DropTable("dbo.Tutorials");65             DropTable("dbo.Schools");66             DropTable("dbo.Posts");67             DropTable("dbo.Blogs");68         }69     }

此时我们要做的只要把这个文件名201503190341085_addmodels.cs对应在数据迁移表中的记录删除，

delete __MigrationHistory where MigrationId = '201503190341085_addmodels' ,然后我们在201503190341085_addmodels.cs注释掉其它的迁移数据，只留下创建shools表的数据

1     public partial class addmodels : DbMigration 2     { 3         public override void Up() 4         { 5             //CreateTable( 6             //    "dbo.Blogs", 7             //    c => new 8             //        { 9             //            BlogId = c.Int(nullable: false, identity: true),10             //            Name = c.String(),11             //            Url = c.String(),12             //        })13             //    .PrimaryKey(t => t.BlogId);14 15             //CreateTable(16             //    "dbo.Posts",17             //    c => new18             //        {19             //            PostId = c.Int(nullable: false, identity: true),20             //            Title = c.String(),21             //            Content = c.String(),22             //            BlogId = c.Int(nullable: false),23             //        })24             //    .PrimaryKey(t => t.PostId)25             //    .ForeignKey("dbo.Blogs", t => t.BlogId, cascadeDelete: true)26             //    .Index(t => t.BlogId);27             28             CreateTable(29                 "dbo.Schools",30                 c => new31                     {32                         SchoolId = c.Int(nullable: false, identity: true),33                         SchoolName = c.String(),34                         SchoolLevel = c.Int(nullable: false),35                     })36                 .PrimaryKey(t => t.SchoolId);37 38             //CreateTable(39             //    "dbo.Tutorials",40             //    c => new41             //        {42             //            Id = c.Int(nullable: false, identity: true),43             //            Name = c.Int(nullable: false),44             //        })45             //    .PrimaryKey(t => t.Id);46 47             //CreateTable(48             //    "dbo.Users",49             //    c => new50             //        {51             //            UserId = c.Int(nullable: false, identity: true),52             //            user_name = c.String(),53             //            display_name = c.String(),54             //        })55             //    .PrimaryKey(t => t.UserId);56             57         }58         59         public override void Down()60         {61             //DropForeignKey("dbo.Posts", "BlogId", "dbo.Blogs");62             //DropIndex("dbo.Posts", new[] { "BlogId" });63             //DropTable("dbo.Users");64             //DropTable("dbo.Tutorials");65             DropTable("dbo.Schools");66             //DropTable("dbo.Posts");67             //DropTable("dbo.Blogs");68         }69     }

此时如果你在package-manager console 中执行update-database 即可完成schools表的恢复

方法二：

利用 Update-Database -Script -SourceMigration $InitialDatabase （这是一个变量不需要你去改成你自己的数据库名字） 或者

Update-Database -Script -SourceMigration Second -TargetMigration First (用这两个中的哪个是视情况而定的) (Second First 就是你的migrations文件夹下的文件名字的后面那个 比喻 201503190906406_addmodels 你就输入 Update-Database -Script -SourceMigration addmodels)

这样会产生一个脚本文件，你在那个脚本文件中找出你恢复的表的一些创建或者修改信息

DECLARE @CurrentMigration [nvarchar](max)IF object_id('[dbo].[__MigrationHistory]') IS NOT NULL    SELECT @CurrentMigration =        (SELECT TOP (1)         [Project1].[MigrationId] AS [MigrationId]        FROM ( SELECT         [Extent1].[MigrationId] AS [MigrationId]        FROM [dbo].[__MigrationHistory] AS [Extent1]        WHERE [Extent1].[ContextKey] = N'EntityFrameworkStudy.Migrations.Configuration'        )  AS [Project1]        ORDER BY [Project1].[MigrationId] DESC)IF @CurrentMigration IS NULL    SET @CurrentMigration = '0'IF @CurrentMigration < '201503190906406_addmodels'BEGIN    CREATE TABLE [dbo].[Blogs] (        [BlogId] [int] NOT NULL IDENTITY,        [Name] [nvarchar](max),        [Url] [nvarchar](max),        CONSTRAINT [PK_dbo.Blogs] PRIMARY KEY ([BlogId])    )    CREATE TABLE [dbo].[Posts] (        [PostId] [int] NOT NULL IDENTITY,        [Title] [nvarchar](max),        [Content] [nvarchar](max),        [BlogId] [int] NOT NULL,        CONSTRAINT [PK_dbo.Posts] PRIMARY KEY ([PostId])    )    CREATE INDEX [IX_BlogId] ON [dbo].[Posts]([BlogId])    CREATE TABLE [dbo].[Schools] (        [SchoolId] [int] NOT NULL IDENTITY,        [SchoolName] [nvarchar](max),        [SchoolLevel] [int] NOT NULL,        CONSTRAINT [PK_dbo.Schools] PRIMARY KEY ([SchoolId])    )    CREATE TABLE [dbo].[Teachers] (        [TecherId] [int] NOT NULL IDENTITY,        [TeacherName] [nvarchar](max),        CONSTRAINT [PK_dbo.Teachers] PRIMARY KEY ([TecherId])    )    CREATE TABLE [dbo].[Tutorials] (        [Id] [int] NOT NULL IDENTITY,        [Name] [int] NOT NULL,        CONSTRAINT [PK_dbo.Tutorials] PRIMARY KEY ([Id])    )    CREATE TABLE [dbo].[Users] (        [UserId] [int] NOT NULL IDENTITY,        [user_name] [nvarchar](max),        [display_name] [nvarchar](max),        CONSTRAINT [PK_dbo.Users] PRIMARY KEY ([UserId])    )    ALTER TABLE [dbo].[Posts] ADD CONSTRAINT [FK_dbo.Posts_dbo.Blogs_BlogId] FOREIGN KEY ([BlogId]) REFERENCES [dbo].[Blogs] ([BlogId]) ON DELETE CASCADE    CREATE TABLE [dbo].[__MigrationHistory] (        [MigrationId] [nvarchar](150) NOT NULL,        [ContextKey] [nvarchar](300) NOT NULL,        [Model] [varbinary](max) NOT NULL,        [ProductVersion] [nvarchar](32) NOT NULL,        CONSTRAINT [PK_dbo.__MigrationHistory] PRIMARY KEY ([MigrationId], [ContextKey])    )    INSERT [dbo].[__MigrationHistory]([MigrationId], [ContextKey], [Model], [ProductVersion])    VALUES (N'201503190906406_addmodels', N'EntityFrameworkStudy.Migrations.Configuration',  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

我找到了Schools的创建SQL ,　在数据库中执行即可：

1      CREATE TABLE [dbo].[Schools] (2         [SchoolId] [int] NOT NULL IDENTITY,3         [SchoolName] [nvarchar](max),4         [SchoolLevel] [int] NOT NULL,5         CONSTRAINT [PK_dbo.Schools] PRIMARY KEY ([SchoolId])6     )

这样你就恢复好了

转载于:https://www.cnblogs.com/bleychen/p/4350913.html

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