EF Core 数据库中已经有一个名为“AspNetRoles”的对象

Question

我收到数据库中已经有一个名为AspNetRoles的对象。 尝试在 NuGet 控制台中使用update-database命令时出错。

语境：

public class ApplicationDbContext : IdentityDbContext<IdentityUser>
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options) { }


    public DbSet<Customer> Customers { get; set; }
}

启动：

public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddDbContext<ApplicationDbContext>(options =>
                options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"),
                b => b.MigrationsAssembly("DroneDeliveryWebApi")));

            // add identity
            var builder = services.AddIdentityCore<AppUser>(o =>
            {
                // configure identity options
                o.Password.RequireDigit = false;
                o.Password.RequireLowercase = false;
                o.Password.RequireUppercase = false;
                o.Password.RequireNonAlphanumeric = false;
                o.Password.RequiredLength = 6;
            });
            builder = new IdentityBuilder(builder.UserType, typeof(IdentityRole), builder.Services);
            builder.AddEntityFrameworkStores<ApplicationDbContext>().AddDefaultTokenProviders();

            services.AddMvc();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseMvc();
        }
    }

appsetting.json:

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=DroneDeliverydb;Trusted_Connection=True;MultipleActiveResultSets=true"
  },
  "Logging": {
    "IncludeScopes": false,
    "Debug": {
      "LogLevel": {
        "Default": "Warning"
      }
    },
    "Console": {
      "LogLevel": {
        "Default": "Warning"
      }
    },
    "JwtIssuerOptions": {
      "Issuer": "DroneDeliveryWebApi",
      "Audience": "http://localhost:5000/"
    }
  }
}

appsetting.Development.json：

{
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
    }
  },

  "JwtIssuerOptions": {
    "Issuer": "DroneDeliveryWebApi",
    "Audience": "http://localhost:5000/"
  }
} 

顾客：

public class Customer
{
    public int Id { get; set; }
    public string IdentityId { get; set; }
    public AppUser Identity { get; set; }
    public string Location { get; set; }
    public string Locale { get; set; }
    public string Gender { get; set; }
}

数据库：

错误：

PM> update-database
Applying migration '20190407181929_initial'.
Failed executing DbCommand (2ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
CREATE TABLE [AspNetRoles] (
    [Id] nvarchar(450) NOT NULL,
    [ConcurrencyStamp] nvarchar(max) NULL,
    [Name] nvarchar(256) NULL,
    [NormalizedName] nvarchar(256) NULL,
    CONSTRAINT [PK_AspNetRoles] PRIMARY KEY ([Id])
);
fail: Microsoft.EntityFrameworkCore.Database.Command[20102]
      Failed executing DbCommand (2ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
      CREATE TABLE [AspNetRoles] (
          [Id] nvarchar(450) NOT NULL,
          [ConcurrencyStamp] nvarchar(max) NULL,
          [Name] nvarchar(256) NULL,
          [NormalizedName] nvarchar(256) NULL,
          CONSTRAINT [PK_AspNetRoles] PRIMARY KEY ([Id])
      );
System.Data.SqlClient.SqlException (0x80131904): There is already an object named 'AspNetRoles' in the database.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite, String methodName)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.Execute(IRelationalConnection connection, DbCommandMethod executeMethod, IReadOnlyDictionary`2 parameterValues)
ClientConnectionId:e40d4c0a-f6df-498d-a92b-06c3711b5106
Error Number:2714,State:6,Class:16
System.Data.SqlClient.SqlException (0x80131904): There is already an object named 'AspNetRoles' in the database.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async, Int32 timeout, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource`1 completion, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite, String methodName)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.Execute(IRelationalConnection connection, DbCommandMethod executeMethod, IReadOnlyDictionary`2 parameterValues)
   at Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand.ExecuteNonQuery(IRelationalConnection connection, IReadOnlyDictionary`2 parameterValues)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationCommand.ExecuteNonQuery(IRelationalConnection connection, IReadOnlyDictionary`2 parameterValues)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationCommandExecutor.ExecuteNonQuery(IEnumerable`1 migrationCommands, IRelationalConnection connection)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.UpdateDatabase(String targetMigration, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabase.<>c__DisplayClass0_1.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
ClientConnectionId:e40d4c0a-f6df-498d-a92b-06c3711b5106
Error Number:2714,State:6,Class:16
There is already an object named 'AspNetRoles' in the database.

您可以向我询问任何其他信息

Answer 1

对于那些和我一样奋斗的人。
解决方案是将数据库的确切连接字符串粘贴到 appsettings.json 和 appsettings.Development.json 中。 因此将创建所有授权表。

但是每次运行“update-database”时错误都会不断出现，并且不会应用任何更改。 因此，您可以在创建所有授权表的迁移中注释Up 方法的内容。

 public partial class initial : Migration
    {
        protected override void Up(MigrationBuilder migrationBuilder)
        {
            //migrationBuilder.CreateTable(
            //    name: "AspNetRoles",
            //    columns: table => new
            //    {
            //        Id = table.Column<string>(nullable: false),
            //        ConcurrencyStamp = table.Column<string>(nullable: true),
            //        Name = table.Column<string>(maxLength: 256, nullable: true),
            //        NormalizedName = table.Column<string>(maxLength: 256, nullable: true)
            //    },
            //    constraints: table =>
            //    {
            //        table.PrimaryKey("PK_AspNetRoles", x => x.Id);
            //    });
            //
            //    ...
        }
    }

在这些更改之后，您将创建表并且不会发生错误。

Answer 2

看起来我们必须在看到此错误时随时删除数据库。

但是，有一种方法可以在重新创建数据库时保留数据：

使用SQL Server Management Studio，我们可以进入Task -> Generate Scripts，然后在“Set Scripting Options”窗口备份数据，我们应该将要备份的数据类型设置为“Data Only”。

然后删除数据库，发出Update-Database命令，运行生成的脚本恢复数据；