指定的 LocalDB 实例名称无效：能够创建迁移但不能运行它们

Question

我创建了一个新的 XAF Blazor 解决方案，并且能够运行它来创建数据库。 然后我按照this question 添加了一个数据库迁移 但是，当我从包管理器中运行迁移时，我得到了

Microsoft.Data.SqlClient.SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SNI_PN11, error: 50 - Local Database Runtime error occurred. Specified LocalDB instance name is invalid.
)
 ---> System.ComponentModel.Win32Exception (0x89C5011B): Unknown error (0x89c5011b)
   at Microsoft.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at Microsoft.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, Boolean withFailover, SqlAuthenticationMethod authType)
   at Microsoft.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, Boolean withFailover)
   at Microsoft.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString connectionOptions, SqlCredential credential, TimeoutTimer timeout)
   at Microsoft.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout, SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance)
   at Microsoft.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, Boolean applyTransientFaultHandling, String accessToken, DbConnectionPool pool)
   at Microsoft.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
   at Microsoft.Data.ProviderBase.DbConnectionFactory.CreateNonPooledConnection(DbConnection owningConnection, DbConnectionPoolGroup poolGroup, DbConnectionOptions userOptions)
   at Microsoft.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at Microsoft.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at Microsoft.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at Microsoft.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry, SqlConnectionOverrides overrides)
   at Microsoft.Data.SqlClient.SqlConnection.Open(SqlConnectionOverrides overrides)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerConnection.OpenDbConnection(Boolean errorsExpected)
   at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenInternal(Boolean errorsExpected)
   at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.Open(Boolean errorsExpected)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerDatabaseCreator.<>c__DisplayClass18_0.<Exists>b__0(DateTime giveUp)
   at Microsoft.EntityFrameworkCore.ExecutionStrategyExtensions.<>c__DisplayClass12_0`2.<Execute>b__0(DbContext c, TState s)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
   at Microsoft.EntityFrameworkCore.ExecutionStrategyExtensions.Execute[TState,TResult](IExecutionStrategy strategy, TState state, Func`2 operation, Func`2 verifySucceeded)
   at Microsoft.EntityFrameworkCore.ExecutionStrategyExtensions.Execute[TState,TResult](IExecutionStrategy strategy, TState state, Func`2 operation)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerDatabaseCreator.Exists(Boolean retryOnNotExists)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerDatabaseCreator.Exists()
   at Microsoft.EntityFrameworkCore.Migrations.HistoryRepository.Exists()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.UpdateDatabase(String targetMigration, String connectionString, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabaseImpl(String targetMigration, String connectionString, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabase.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
ClientConnectionId:00000000-0000-0000-0000-000000000000
Error Number:-1983577829,State:0,Class:20
A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. 
(provider: SNI_PN11, error: 50 - Local Database Runtime error occurred. Specified LocalDB instance name is invalid.
)

这个问题不是 this question about connecting to SQL Server 的重复问题，因为程序可以在我创建迁移之前访问数据库。

[更新]

代码是

    using DevExpress.ExpressApp.EFCore.Updating;
    using Microsoft.EntityFrameworkCore;
    using DevExpress.Persistent.BaseImpl.EF.PermissionPolicy;
    using DevExpress.Persistent.BaseImpl.EF;
    using DevExpress.ExpressApp.Design;
    using DevExpress.ExpressApp.EFCore.DesignTime;
    using DevExpress.Persistent.Base;
    using Microsoft.EntityFrameworkCore.Design;
    namespace ExamBuddy.Module.BusinessObjects {
        public class ExamBuddyContextInitializer : DbContextTypesInfoInitializerBase {
            protected override DbContext CreateDbContext() {
                var builder = new DbContextOptionsBuilder<ExamBuddyEFCoreDbContext>()
                    .UseSqlServer(@";");
                return new ExamBuddyEFCoreDbContext(builder.Options);
            }
        }
        public class ExamBuddyContextFactory : IDesignTimeDbContextFactory<ExamBuddyEFCoreDbContext>
        {
            public ExamBuddyEFCoreDbContext CreateDbContext(string[] args)
            {
                var optionsBuilder = new DbContextOptionsBuilder<ExamBuddyEFCoreDbContext>();
                optionsBuilder.UseSqlServer(@"Integrated Security=SSPI;MultipleActiveResultSets=true;Pooling=false;Data Source=(localdb)\\mssqllocaldb;Initial Catalog=ExamBuddy;ConnectRetryCount=0;");
                return new ExamBuddyEFCoreDbContext(optionsBuilder.Options);
            }
        }
        [TypesInfoInitializer(typeof(ExamBuddyContextInitializer))]
        public class ExamBuddyEFCoreDbContext : DbContext {
            public ExamBuddyEFCoreDbContext(DbContextOptions<ExamBuddyEFCoreDbContext> options) : base(options) {
                 
            }
            public DbSet<ModuleInfo> ModulesInfo { get; set; }
            public DbSet<ModelDifference> ModelDifferences { get; set; }
            public DbSet<ModelDifferenceAspect> ModelDifferenceAspects { get; set; }
            public DbSet<PermissionPolicyRole> Roles { get; set; }
            public DbSet<PermissionPolicyRoleBase> RolesBase { get; set; }
            public DbSet<PermissionPolicyUser> Users { get; set; }
        }

[更新]

我尝试注释掉 Dev Express TypesInfoInitializer 属性 我尝试添加以下内容，但它没有执行（错误不会抛出）而如果我在 IDesignTimeDbContextFactory 方法中输入错误，它将抛出

public class MigrationsContextFactory : IDbContextFactory<ExamBuddyEFCoreDbContext>
{
    public ExamBuddyEFCoreDbContext CreateDbContext()
    {
        throw new Exception("In Migration Context");
        var optionsBuilder = new DbContextOptionsBuilder<ExamBuddyEFCoreDbContext>();
        optionsBuilder.UseSqlServer(@"Integrated Security=SSPI;MultipleActiveResultSets=true;Pooling=false;Data Source=(localdb)\\mssqllocaldb;Initial Catalog=ExamBuddy;ConnectRetryCount=0;");
        return new ExamBuddyEFCoreDbContext(optionsBuilder.Options);
    }
}

ExamBuddyContextFactory 方法会执行

[更新]

当我编辑连接字符串以仅使用 1 个反斜杠时，我在 Visual Studio 2019 中看到以下消息

因此迁移将在连接字符串中生成双反斜杠，但不会运行。

Answer 1

异常信息告诉你问题

指定的 LocalDB 实例名称无效

无效部分是C# verbatim string literal内(localdb)\\mssqllocaldb中的双反斜杠

optionsBuilder.UseSqlServer(
    @"Data Source=(localdb)\\mssqllocaldb;Integrated Security=SSPI;MultipleActiveResultSets=true;Pooling=false;Initial Catalog=ExamBuddy;ConnectRetryCount=0;");
//  ^                       ^

实际名称是(localdb)\mssqllocaldb（单反斜杠），所以要么更正它，要么删除逐字字符串前缀@。

所有这些只是标准的 C# 字符串规则，没有什么特别要讨论的。那为什么

能够创建迁移但不能运行它们？

这是因为Add-Migration命令没有尝试连接数据库，数据库连接只有在需要的时候才延迟初始化，所以没有检测到无效的连接字符串。该命令仍然需要创建 DbContext 实例才能访问 model，并且必须为特定的数据库提供程序 type 配置上下文（因为 EF Core 为每个数据库提供程序类型创建单独的模型)，但除此之外它与实际数据库无关。

但是Update-Database命令显然需要数据库连接，而Remove-Migration命令需要检查迁移是否已经应用。这就是为什么这些命令失败而 Add-Migration 成功的原因。

您可以通过提供虚假的无效连接字符串来轻松验证，例如

optionsBuilder.UseSqlServer("Blah")'

并观察与 OP 中完全相同的行为。