尝试创建数据库时出错：建立与 SQL Server 的连接时发生与网络相关或特定于实例的错误

我正在尝试在 ASP.NET 中编写应用程序，已经创建了模型、上下文并希望使用 EF Code-First 方法创建数据库，但它不起作用。

此外，文件夹App_Data是空的。我已经安装了 SQL Server 2017 Express。

我尝试了我能找到的所有可能的解决方案，但仍然没有任何效果。

连接字符串：

<connectionStrings>
    <add name="DefaultConnection" 
         connectionString="Data Source=(LocalDb)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\aspnet-BM-20171207072135.mdf;Initial Catalog=aspnet-BM-20171207072135;Integrated Security=True" 
         providerName="System.Data.SqlClient" />
</connectionStrings>

但是，我收到此错误：

PM> update-database 

> Specify the '-Verbose' flag to view the SQL
> statements being applied to the target database

System.Data.SqlClient.SqlException (0x80131904)：建立与 SQL Server 的连接时发生与网络相关或特定于实例的错误。服务器未找到或无法访问。验证实例名称是否正确以及 SQL Server 是否配置为允许远程连接。（提供程序：SQL 网络接口，错误：
发生50本地数据库运行时错误。LocalDB 实例启动期间发生错误：SQL Server 进程无法启动。

错误：
在 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, DbConnectionPool System and String AccessToken at .Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions 选项, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions) 在 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningKey, PoolConnectionOptions)DbConnectionOptions userOptions) at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) at System.DataProvider DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) 在 System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSourceDbConnectionInternal oldConnection) 在 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) 在 System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, One Boolean allowCheckConnections, userOptions only, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)连接）在 System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSourceDbConnectionInternal oldConnection) 在 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) 在 System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, One Boolean allowCheckConnections, userOptions only, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)连接）在 System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSourceBoolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSourceBoolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource1重试，DbConnectionOptions USEROPTIONS，DbConnectionInternal oldConnection，DbConnectionInternal＆连接）在System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal（的DbConnection outerConnection，DbConnectionFactory connectionFactory的，TaskCompletionSource 1 retry, DbConnectionOptions userOptions) at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource1重试，DbConnectionOptions USEROPTIONS）在System.Data.SqlClient.SqlConnection.TryOpenInner（TaskCompletionSource 1 retry) at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource1重试) 在 System.Data.SqlClient.SqlConnection.Open() 在 System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.b__36(DbConnection t, DbConnectionInterceptionContext c) 在 System.Data.Entity.Infrastructure.Interception.InternalDispatcher 1.Dispatch[TTarget,TInterceptionContext](TTarget target, Action2 操作，TInterceptionContext拦截上下文，动作3 executing, Action3 在 System.Data.Entity.Infrastructure.Interception.DbConnectionDispatcher.Open(DbConnection 连接，DbInterceptionContext 拦截上下文) 在 System.Data.Entity.SqlServer.SqlProviderServices.<>c__DisplayClass33.b__32() 在 System.Data.Entity.SqlServer 上执行) .DefaultSqlExecutionStrategy.<>c__DisplayClass1.b__0() 在 System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func 1 operation) at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Action operation) at System.Data.Entity.SqlServer.SqlProviderServices.UsingConnection(DbConnection sqlConnection, Action1 act) 在 System.Data.Entity.SqlServer.SqlProviderServices.UsingMasterConnection(DbConnection sqlConnection, Action 1 act) at System.Data.Entity.SqlServer.SqlProviderServices.CreateDatabaseFromScript(Nullable1 commandTimeout, DbConnection sqlConnection, String createDatabaseScript) 在 System.Data.Entity.SqlServer.SqlProviderServices.DbCreateDatabase(DbConnection connection, Nullable1 commandTimeout, StoreItemCollection storeItemCollection) at System.Data.Entity.Core.Common.DbProviderServices.CreateDatabase(DbConnection connection, Nullable1 commandTimeout, StoreItemCollection storeItemCollection) at System.Data.Entity.Core.Objects.ObjectContext.CreateDatabase() at System.Data.Entity.Migrations.Utilities.DatabaseCreator.Create(DbConnection connection) at System.Data.Entity.Migrations.DbMigrator .EnsureDatabaseExists(Action mustSucceedToKeepDatabase) at System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase) at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration) at System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Action mustSucceedToKeepDatabase) .MigratorBase.Update(String targetMigration) 在 System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.RunCore() 在 System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run() ClientConnectionId:00000000-0000- 0000-0000-000000000000

>

错误编号：-1983577846，状态：0，类别：20
与 SQL Server 建立连接时发生与网络相关或特定于实例的错误。服务器未找到或无法访问。验证实例名称是否正确以及 SQL Server 是否配置为允许远程连接。（提供程序：SQL 网络接口，错误：50 - 发生本地数据库运行时错误。LocalDB 实例启动期间发生错误：SQL Server 进程无法启动）