mscorlib.dll 中发生类型 'System.Data.SqlClient.SqlException' 的异常，但未在用户代码中处理
An exception of type 'System.Data.SqlClient.SqlException' occurred in mscorlib.dll but was not handled in user code
所以，我正在尝试使用 C# 制作一个 ASP.NET Web 表单应用程序（请注意，我是 ASP 和 C# 的绝对初学者）。我正在按照位于此处的教程进行操作：
我在 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 服务器版本）。
现在，我在 VS2013 上编写本教程，在构建和 运行ning 程序后，它可以正常工作。将其移植到 VS2015 并 运行 运行该程序后，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.)
这是源错误代码块（它特别出现在第 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，应用程序都会 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。这是我看到的代码部分（经过一些 Google 研究），我认为它是相关的：
<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，以便也许有人能够帮助我解决这个问题。从 2015 年到 2013 年 运行ning 期间，代码或任何配置是否有任何更改会导致此问题？
在此先感谢您。
您需要检查实例是否存在。
尝试通过 cmd 提示 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。
所以，我正在尝试使用 C# 制作一个 ASP.NET Web 表单应用程序（请注意，我是 ASP 和 C# 的绝对初学者）。我正在按照位于此处的教程进行操作：
我在 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 服务器版本）。
现在，我在 VS2013 上编写本教程，在构建和 运行ning 程序后，它可以正常工作。将其移植到 VS2015 并 运行 运行该程序后，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.)
这是源错误代码块（它特别出现在第 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，应用程序都会 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。这是我看到的代码部分（经过一些 Google 研究），我认为它是相关的：
<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，以便也许有人能够帮助我解决这个问题。从 2015 年到 2013 年 运行ning 期间，代码或任何配置是否有任何更改会导致此问题？
在此先感谢您。
您需要检查实例是否存在。 尝试通过 cmd 提示 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。