LocalDB .mdf 文件未在连接字符串中使用 AttachDbFileName 自动附加

Question

我期待这种行为是因为this MSDN article about the AttachDbFileName property

第一次使用此选项连接到数据库时 连接字符串，SQL Server Express 或 LocalDB 实例附加 数据库，并且它保持连接状态。当您想要连接到 将来您可以使用相同的数据库，而无需使用初始目录 如果您愿意，可以附加 DbFileName。

我有一个实体框架使用的连接字符串：

<add name="DatabaseContext" providerName="System.Data.SqlClient" connectionString="Server=(localdb)\MSSQLLocalDB;Database=DatabaseName;Integrated Security=True;AttachDbFileName=|DatabaseName|\DatabaseName.mdf" />

在我在 SQL Management Studio 中打开数据库后，这工作正常，将 AttachDbFileName 值与绝对路径作为附加参数提供给它。

但是，如果我没有先将它附加到 SQL Management Studio，那么在尝试在数据库上运行 EF 迁移时会出现以下错误：

System.Data.SqlClient.SqlException (0x80131904): Cannot create file 'C:\Users\user\Desktop\folder\DatabaseName.mdf' because it already exists. Change the file path or the file name, and retry the operation.
CREATE DATABASE failed. Some file names listed could not be created. Check related errors.
   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, String methodName, Boolean sendToPipe, Int32 timeout, Boolean asyncWrite)
   at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
   at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.<NonQuery>b__0(DbCommand t, DbCommandInterceptionContext`1 c)
   at System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target, Func`3 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed)
   at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.NonQuery(DbCommand command, DbCommandInterceptionContext interceptionContext)
   at System.Data.Entity.SqlServer.SqlProviderServices.<>c__DisplayClass1a.<CreateDatabaseFromScript>b__19(DbConnection conn)
   at System.Data.Entity.SqlServer.SqlProviderServices.<>c__DisplayClass33.<UsingConnection>b__32()
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.<>c__DisplayClass1.<Execute>b__0()
   at 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, Action`1 act)
   at System.Data.Entity.SqlServer.SqlProviderServices.UsingMasterConnection(DbConnection sqlConnection, Action`1 act)
   at System.Data.Entity.SqlServer.SqlProviderServices.CreateDatabaseFromScript(Nullable`1 commandTimeout, DbConnection sqlConnection, String createDatabaseScript)
   at System.Data.Entity.SqlServer.SqlProviderServices.DbCreateDatabase(DbConnection connection, Nullable`1 commandTimeout, StoreItemCollection storeItemCollection)
   at System.Data.Entity.Core.Common.DbProviderServices.CreateDatabase(DbConnection connection, Nullable`1 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.DbMigrator.Update(String targetMigration)
   at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update()

这看起来好像由于某种原因它没有自动附加数据库，然后尝试创建它，就好像文件不存在一样。

是否有额外的连接字符串选项或 LocalDB 配置可以解决此问题，以便在第一个连接上自动附加数据库？

Answer 1

答案很简单：.mdf 和 .ldf 文件是在较新版本的 SQL Server 中创建的，因此旧版本不会附加它们，就好像它们不存在一样。