EF7使用SQLite生成错误的迁移

Question

我尝试将ASP.Net 5与Entity Framework 7和SQLite一起使用,我发现了一个奇怪的迁移器行为.

我删除了Visual Studio 2015并使用模板"ASP.NET 5 Template Web Application"创建了一个新项目.

之后我删除了依赖

"EntityFramework.MicrosoftSqlServer": "7.0.0-rc1-final"

并添加了两个依赖项,而不是称为还原包.

"EntityFramework.Sqlite": "7.0.0-rc1-final",
"Microsoft.Data.Sqlite": "1.0.0-rc1-final"

像那样

"dependencies": {
"EntityFramework.Commands": "7.0.0-rc1-final",
"EntityFramework.Sqlite": "7.0.0-rc1-final",
"Microsoft.Data.Sqlite": "1.0.0-rc1-final",
"Microsoft.AspNet.Authentication.Cookies": "1.0.0-rc1-final",
"Microsoft.AspNet.Diagnostics.Entity": "7.0.0-rc1-final",
"Microsoft.AspNet.Identity.EntityFramework": "3.0.0-rc1-final",
"Microsoft.AspNet.IISPlatformHandler": "1.0.0-rc1-final",
"Microsoft.AspNet.Mvc": "6.0.0-rc1-final",
"Microsoft.AspNet.Mvc.TagHelpers": "6.0.0-rc1-final",
"Microsoft.AspNet.Server.Kestrel": "1.0.0-rc1-final",
"Microsoft.AspNet.StaticFiles": "1.0.0-rc1-final",
"Microsoft.AspNet.Tooling.Razor": "1.0.0-rc1-final",
"Microsoft.Extensions.CodeGenerators.Mvc": "1.0.0-rc1-final",
"Microsoft.Extensions.Configuration.FileProviderExtensions": "1.0.0-rc1-final",
"Microsoft.Extensions.Configuration.Json": "1.0.0-rc1-final",
"Microsoft.Extensions.Configuration.UserSecrets": "1.0.0-rc1-final",
"Microsoft.Extensions.Logging": "1.0.0-rc1-final",
"Microsoft.Extensions.Logging.Console": "1.0.0-rc1-final",
"Microsoft.Extensions.Logging.Debug": "1.0.0-rc1-final",
"Microsoft.VisualStudio.Web.BrowserLink.Loader": "14.0.0-rc1-final"
}

接下来,我转到Startup.cs并更改了这样的ConfigurationServices功能

 public void ConfigureServices(IServiceCollection services)
    {
        // Add framework services.
        var dbFilePath =     Path.Combine(PlatformServices.Default.Application.ApplicationBasePath, "test.db");
        services.AddEntityFramework()
         .AddSqlite()
         .AddDbContext<ApplicationDbContext>(options =>
             options.UseSqlite("Filename=" + dbFilePath));
        System.Console.WriteLine("Use DB file:" + dbFilePath);

        services.AddIdentity<ApplicationUser, IdentityRole>()
            .AddEntityFrameworkStores<ApplicationDbContext>()
            .AddDefaultTokenProviders();

        services.AddMvc();

        // Add application services.
        services.AddTransient<IEmailSender, AuthMessageSender>();
        services.AddTransient<ISmsSender, AuthMessageSender>();
        services.AddInstance<IConfigurationRoot>(Configuration);
    }

然后我从文件夹"Migrations"中删除了所有文件并构建了解决方案.所有人都已准备好创建迁移.我在项目文件夹上运行git bash并在下一个命令之间运行:

blush@BLUSH /d/dev/testMVC
$ dnx ef migrations add firstMigration
Use DB file:D:\dev\testMVC\test.db
Done. To undo this action, use 'ef migrations remove'

和

$ dnx ef database update
Use DB file:D:\dev\testMVC\test.db
Applying migration '20160304130532_firstMigration'.
Done.

好的,我在"迁移"文件夹中看到了一个数据库文件和文件.而且我猜想下一次生成的迁移将是空的,而不会更改对象模型.我试着这样做并输入下一个命令:

$ dnx ef migrations add testMigration
Use DB file:D:\dev\testMVC\test.db
Done. To undo this action, use 'ef migrations remove'

我去看了一个生成的迁移类,我看到了这段代码:

 protected override void Up(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.DropForeignKey(name: "FK_IdentityRoleClaim<string>_IdentityRole_RoleId", table: "AspNetRoleClaims");
            migrationBuilder.DropForeignKey(name: "FK_IdentityUserClaim<string>_ApplicationUser_UserId", table: "AspNetUserClaims");
            migrationBuilder.DropForeignKey(name: "FK_IdentityUserLogin<string>_ApplicationUser_UserId", table: "AspNetUserLogins");
            migrationBuilder.DropForeignKey(name: "FK_IdentityUserRole<string>_IdentityRole_RoleId", table: "AspNetUserRoles");
            migrationBuilder.DropForeignKey(name: "FK_IdentityUserRole<string>_ApplicationUser_UserId", table: "AspNetUserRoles");
            migrationBuilder.AddForeignKey(
                name: "FK_IdentityRoleClaim<string>_IdentityRole_RoleId",
                table: "AspNetRoleClaims",
                column: "RoleId",
                principalTable: "AspNetRoles",
                principalColumn: "Id",
                onDelete: ReferentialAction.Cascade);
            migrationBuilder.AddForeignKey(
                name: "FK_IdentityUserClaim<string>_ApplicationUser_UserId",
                table: "AspNetUserClaims",
                column: "UserId",
                principalTable: "AspNetUsers",
                principalColumn: "Id",
                onDelete: ReferentialAction.Cascade);
            migrationBuilder.AddForeignKey(
                name: "FK_IdentityUserLogin<string>_ApplicationUser_UserId",
                table: "AspNetUserLogins",
                column: "UserId",
                principalTable: "AspNetUsers",
                principalColumn: "Id",
                onDelete: ReferentialAction.Cascade);
            migrationBuilder.AddForeignKey(
                name: "FK_IdentityUserRole<string>_IdentityRole_RoleId",
                table: "AspNetUserRoles",
                column: "RoleId",
                principalTable: "AspNetRoles",
                principalColumn: "Id",
                onDelete: ReferentialAction.Cascade);
            migrationBuilder.AddForeignKey(
                name: "FK_IdentityUserRole<string>_ApplicationUser_UserId",
                table: "AspNetUserRoles",
                column: "UserId",
                principalTable: "AspNetUsers",
                principalColumn: "Id",
                onDelete: ReferentialAction.Cascade);
        }

        protected override void Down(MigrationBuilder migrationBuilder)
        {
       ... 
       }

如果我尝试应用此迁移,请捕获下一条错误消息:

$ dnx ef database update
Use DB file:D:\dev\testMVC\test.db
Applying migration '20160304133144_testMigration'.
System.NotSupportedException: SQLite cannot support this migration operation.
   ? Microsoft.Data.Entity.Migrations.SqliteMigrationsSqlGenerator.Generate(Drop
ForeignKeyOperation operation, IModel model, RelationalCommandListBuilder builde
r)
   ? Microsoft.Data.Entity.Migrations.MigrationsSqlGenerator.<>c.<.cctor>b__50_1
0(MigrationsSqlGenerator g, MigrationOperation o, IModel m, RelationalCommandLis
tBuilder b)
   ? Microsoft.Data.Entity.Migrations.MigrationsSqlGenerator.Generate(MigrationO
peration operation, IModel model, RelationalCommandListBuilder builder)
   ? Microsoft.Data.Entity.Migrations.MigrationsSqlGenerator.Generate(IReadOnlyL
ist`1 operations, IModel model)
   ? Microsoft.Data.Entity.Migrations.SqliteMigrationsSqlGenerator.Generate(IRea
dOnlyList`1 operations, IModel model)
   ? Microsoft.Data.Entity.Migrations.Internal.Migrator.GenerateUpSql(Migration
migration)
   ? Microsoft.Data.Entity.Migrations.Internal.Migrator.<>c__DisplayClass12_4.<G
etMigrationCommands>b__10()
   ? Microsoft.Data.Entity.Migrations.Internal.Migrator.Migrate(String targetMig
ration)
   ? Microsoft.Data.Entity.Design.MigrationsOperations.UpdateDatabase(String tar
getMigration, String contextType)
   ? Microsoft.Data.Entity.Commands.Program.Executor.<>c__DisplayClass7_0.<Updat
eDatabase>b__0()
   ? Microsoft.Data.Entity.Commands.Program.Executor.Execute(Action action)
SQLite cannot support this migration operation.

这是一个问题:我将如何解决这个问题？

Answer 1

这是SQLite的限制.请参阅EF中的SQLite限制.

这是因为SQLite本身不支持"ADD FOREIGN KEY".解决此问题的方法是进行表重建.在sqlite.org上进行其他类型的表模式更改提供了有关如何构造查询以执行此操作的说明.您很快就会发现SQLite有多乱,以及为什么EF不能为您自动化.

如果您不需要SQLite数据库中的数据,那么最好只删除它并使用context.Database.EnsureCreated()新模型从头开始重建表.

Answer 2

在Mac上使用Visual Studio Community 2017时发生此问题

我发现最简单的方法是删除数据库并重新创建迁移。因为该项目处于开发的早期阶段，所以我当然能够负担得起：

1. 删除数据库文件（app.db）
2. 发出命令，dotnet ef migrations remove直到只有第一个迁移（00000000000000_CreateIdentitySchema）
3. 添加新的迁移dotnet ef migrations add CreatedEntities（例如）
4. 更新数据库 dotnet ef database update