mscorlib.dll 中出现“System.Data.SqlClient.SqlException”类型的异常，但未在用户代码中处理

Question

所以，我正在尝试使用 C# 制作一个 ASP.NET Web 窗体应用程序（请注意，我是 ASP 和 C# 的绝对初学者）。我正在关注位于此处的教程：

https://docs.microsoft.com/en-us/aspnet/web-forms/overview/getting-started/getting-started-with-aspnet-45-web-forms/membership-and-administration

我在这台 Windows 7（64 位）机器上使用 Visual Studio 2013 和 SQL Server 2012 Express LocalDB。但是，当我在学校时，我在 Windows 10（64 位）机器上使用 Visual Studio 2015（具有相同的 SQL Server 版本）。

现在，我在上面的 VS2013 上编写本教程，在构建和运行程序之后，它可以工作了。将其移植到 VS2015 并运行程序后，我无法在 VS2013 上再次运行它。相反，我遇到了一个错误。

这是完整的错误文本：

An exception of type 'System.Data.SqlClient.SqlException' occurred in 
mscorlib.dll but was not handled in user code

Additional information: 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: SQL 
Network Interfaces, error: 50 - Local Database Runtime error occurred. The 
specified LocalDB instance does not exist.)

这里是源错误代码块（具体出现在第 24 行）：

Line 22:             var roleMgr = new RoleManager<IdentityRole>(roleStore);
Line 23: 
Line 24:             if (!roleMgr.RoleExists("canEdit"))
Line 25:                 IdRoleResult = roleMgr.Create(new IdentityRole { Name = "canEdit" });
Line 26: 

这是错误页面上显示的堆栈跟踪：

[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: SQL Network Interfaces, error: 50 - Local Database Runtime error occurred. The specified LocalDB instance does not exist.
)]
   System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool pool, String accessToken, Boolean applyTransientFaultHandling) +821
   System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions) +332
   System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions) +38
   System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) +699
   System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) +89
   System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) +426
   System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) +78
   System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection) +191
   System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +154
   System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +21
   System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry) +90
   System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry) +217
   System.Data.SqlClient.SqlConnection.Open() +96
   System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.<Open>b__36(DbConnection t, DbConnectionInterceptionContext c) +36
   System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch(TTarget target, Action`2 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed) +138
   System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.Open(DbConnection connection, DbInterceptionContext interceptionContext) +477
   System.Data.Entity.SqlServer.<>c__DisplayClass33.<UsingConnection>b__32() +520
   System.Data.Entity.SqlServer.<>c__DisplayClass1.<Execute>b__0() +34
   System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Func`1 operation) +251
   System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Action operation) +196
   System.Data.Entity.SqlServer.SqlProviderServices.UsingConnection(DbConnection sqlConnection, Action`1 act) +276
   System.Data.Entity.SqlServer.SqlProviderServices.UsingMasterConnection(DbConnection sqlConnection, Action`1 act) +545
   System.Data.Entity.SqlServer.SqlProviderServices.CreateDatabaseFromScript(Nullable`1 commandTimeout, DbConnection sqlConnection, String createDatabaseScript) +151
   System.Data.Entity.SqlServer.SqlProviderServices.DbCreateDatabase(DbConnection connection, Nullable`1 commandTimeout, StoreItemCollection storeItemCollection) +287
   System.Data.Entity.Core.Common.DbProviderServices.CreateDatabase(DbConnection connection, Nullable`1 commandTimeout, StoreItemCollection storeItemCollection) +111
   System.Data.Entity.Core.Objects.ObjectContext.CreateDatabase() +236
   System.Data.Entity.Migrations.Utilities.DatabaseCreator.Create(DbConnection connection) +143
   System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Action mustSucceedToKeepDatabase) +207
   System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase) +42
   System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration) +136
   System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update() +33
   System.Data.Entity.Internal.DatabaseCreator.CreateDatabase(InternalContext internalContext, Func`3 createMigrator, ObjectContext objectContext) +175
   System.Data.Entity.Internal.InternalContext.CreateDatabase(ObjectContext objectContext, DatabaseExistenceState existenceState) +150
   System.Data.Entity.Database.Create(DatabaseExistenceState existenceState) +444
   System.Data.Entity.CreateDatabaseIfNotExists`1.InitializeDatabase(TContext context) +290
   System.Data.Entity.Internal.<>c__DisplayClassf`1.<CreateInitializationAction>b__e() +165
   System.Data.Entity.Internal.InternalContext.PerformInitializationAction(Action action) +110
   System.Data.Entity.Internal.InternalContext.PerformDatabaseInitialization() +660
   System.Data.Entity.Internal.LazyInternalContext.<InitializeDatabase>b__4(InternalContext c) +31
   System.Data.Entity.Internal.RetryAction`1.PerformAction(TInput input) +143
   System.Data.Entity.Internal.LazyInternalContext.InitializeDatabaseAction(Action`1 action) +292
   System.Data.Entity.Internal.LazyInternalContext.InitializeDatabase() +123
   System.Data.Entity.Internal.InternalContext.Initialize() +42
   System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType) +39
   System.Data.Entity.Internal.Linq.InternalSet`1.Initialize() +137
   System.Data.Entity.Internal.Linq.InternalSet`1.get_InternalContext() +38
   System.Data.Entity.Infrastructure.DbQuery`1.System.Linq.IQueryable.get_Provider() +99
   System.Data.Entity.QueryableExtensions.FirstOrDefaultAsync(IQueryable`1 source, Expression`1 predicate, CancellationToken cancellationToken) +197
   System.Data.Entity.QueryableExtensions.FirstOrDefaultAsync(IQueryable`1 source, Expression`1 predicate) +233
   Microsoft.AspNet.Identity.EntityFramework.RoleStore`3.FindByNameAsync(String roleName) +1120
   Microsoft.AspNet.Identity.<FindByNameAsync>d__13.MoveNext() +278
   System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +99
   System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +58
   System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() +28
   Microsoft.AspNet.Identity.CultureAwaiter`1.GetResult() +123
   Microsoft.AspNet.Identity.<RoleExistsAsync>d__d.MoveNext() +612
   System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +99
   System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +58
   System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() +28
   Microsoft.AspNet.Identity.AsyncHelper.RunSync(Func`1 func) +244
   Microsoft.AspNet.Identity.RoleManagerExtensions.RoleExists(RoleManager`2 manager, String roleName) +241
   Starlane.Logic.RoleActions.AddUserAndRole() in F:\WEBENGINEERING\Starlane\Starlane\Logic\RoleActions.cs:24
   Starlane.Global.Application_Start(Object sender, EventArgs e) in F:\WEBENGINEERING\Starlane\Starlane\Global.asax.cs:28

[HttpException (0x80004005): 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: SQL Network Interfaces, error: 50 - Local Database Runtime error occurred. The specified LocalDB instance does not exist.
)]
   System.Web.HttpApplicationFactory.EnsureAppStartCalledForIntegratedMode(HttpContext context, HttpApplication app) +10063289
   System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +118
   System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +173
   System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +336
   System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +296

[HttpException (0x80004005): 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: SQL Network Interfaces, error: 50 - Local Database Runtime error occurred. The specified LocalDB instance does not exist.
)]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +10044576
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +95
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +254

每当我注释掉任何使用 roleMgr var 的代码行时，应用程序就会运行，但是当我尝试测试登录系统时遇到相同的 SqlException 错误。我在想这可以通过我的 Web.Config 文件来纠正。这是我看到的（经过一些 Google 研究）我认为可能相关的部分代码：

<connectionStrings>
    <add name="DefaultConnection" connectionString="Data Source=(LocalDb)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\aspnet-Starlane-20170802095040.mdf;Initial Catalog=aspnet-Starlane-20170802095040;Integrated Security=True" providerName="System.Data.SqlClient"/>
    <add name="Starlane" connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\starlane.mdf;Integrated Security=True" providerName="System.Data.SqlClient"/>
  </connectionStrings>

使用服务器资源管理器，我可以查询 Starlane 数据库，但不能查询默认连接数据库。

无论如何，我希望我提供了足够的信息，以便有人能够帮助我解决这个问题。从 2015 年到 2013 年运行时，代码或任何配置是否有任何变化会导致此问题？

非常感谢您。

Answer 1

您需要检查实例是否存在。 尝试通过 cmd 提示符运行 sqllocaldb.exe。

使用“sqllocaldb i”列出所有 LocalDB 实例。 使用“sqllocaldb create instance name”创建新实例。 使用“sqllocaldb start instance name”启动它。