Se vuoi creare un indice e velocizzare la query, aggiungi l'attributo [Index] all'attributo e genera automaticamente il codice come segue:
Aggiorniamo il database del database e l'errore è il seguente:
System.Data.SqlClient.SqlException (0x80131904): tabella 'dbo. La colonna 'Telefono' in 'Conto' non può essere usata come colonna chiave in un indice.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action'1 wrapCloseInAction)
at System.Data.SqlClient.SqlInternalConnection.OnError(eccezione SqlException, Boolean breakConnection, Action'1 wrapCloseInAction)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
In System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(StringMethodName, Boolean async, timeout Int32, Boolean asyncWrite)
In System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource'1 completion, String methodName, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry)
In System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
In System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher. <NonQuery>b__0(DbComando t, DbComandoContestoInterception'1 c)
In System.Data.Entity.Infrastructure.Interception.InternalDispatcher'1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target, Func'3 operation, TInterceptionContext intercettazioneContesto, Azione'3 in esecuzione, Azione'3 eseguita)
In System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.NonQuery(comando DbComando, DbComandoInterceptionContestoIntercettazioneContestoIntercettazioneContesto)
In System.Data.Entity.Internal.InterceptableDbCommand.ExecuteNonQuery()
In System.Data.Entity.Migrations.DbMigrator.ExecuteSQL (MigrationStatement migrationStatement, DbConnection connection, DbTransaction transaction, DbInterceptionContest intercettazioneContesto)
In System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ExecuteSql(MigrationStatement migrationStatement, connessione DbConnection, transazione DbTransaction , DbIntercettazioneContestoIntercettazioneContesto)
In System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsInternal(IEnumerable'1 migrationStatements, connessione DbConnection, transazione DbTransaction, DbInterceptionContestoInterceptionContesto)
In System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsWithinTransaction(IEnumerable'1 migrationStatements, DbTransaction transaction, DbInterceptionContext intercettazioneContesto)
In System.Data.Entity.Migrations.DbMigrator.ExecuteStatementWithinNewTransaction(IEnumerable'1 migrationStatements, connessione DbConnection, DbInterceptionContest intercettazioneContesto)
In System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsInternal(IEnumerable'1 migrationStatements, DbConnection connection, DbInterceptionContest interceptionInterceptionContest)
presso System.Data.Entity.Migrations.DbMigrator.ExecuteStatementsInternal(IEnumerable'1 migrationStatements, connessione DbConnection)
su System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClass32. <ExecuteStatements>b__30()
In System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.<>c__DisplayClass1. <Execute>b__0()
at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](operazione Func'1)
In System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute(Action operation)
In System.Data.Entity.Migrations.DbMigrator.ExecuteStatements(IEnumerable'1 migrationStatements, DbTransaction existingTransaction)
In System.Data.Entity.Migrations.DbMigrator.ExecuteStatements(IEnumerable'1 migrationStatements)
su System.Data.Entity.Migrations.Infrastructure.MigratorBase.ExecuteStatements(IEnumerable'1 migrationStatements)
In System.Data.Entity.Migrations.DbMigrator.ExecuteOperations(String migrationId, VersionedModel targetModel, IEnumerable'1 operations, IEnumerable'1 systemOperations, Boolean downgrade, auto booleana)
su System.Data.Entity.Migrations.DbMigrator.ApplyMigration(DbMigration migration, DbMigration lastMigration)
su System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ApplyMigration(DbMigration migration, DbMigration lastMigration)
at System.Data.Entity.Migrations.DbMigrator.Upgrade(IEnumerable'1 pending Migrations, Stringa targetMigrationId, stringa lastMigrationId)
su System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.Upgrade(IEnumerable'1 pending Migrations, Stringa targetMigrationId, Stringa lastMigrationId)
su System.Data.Entity.Migrations.DbMigrator.UpdateInternal(StringTargetMigration)
In System.Data.Entity.Migrations.DbMigrator.<>c__DisplayClasse. <Update>b__d()
presso System.Data.Entity.Migrations.DbMigrator.EnsureDatabaseExists(Azione devoSuccedereMantenereDatabase)
su System.Data.Entity.Migrations.Infrastructure.MigratorBase.EnsureDatabaseExists(Azione dovetSuccedereMantenerDatabase)
su System.Data.Entity.Migrations.DbMigrator.Update(Stringa targetMigration)
In System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(StringTargetMigration)
su System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.RunCore()
In System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run()
ClientConnectionId:2b5f614b-caab-4be6-bc1b-a813b7356739
Numero di errore: 1919, Stato: 1, Classe: 16
Tavolo 'dbo. La colonna 'Telefono' in 'Conto' non può essere usata come colonna chiave in un indice.
La ragione dell'errore è che tutte le proprietà della stringa ef sono di tipo NVARCHAR(Max) di default,
La soluzione è la seguente:
Esegui la lunghezza della corda
Come mostrato nell'immagine, la creazione ha avuto successo!
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Pubblicato su 23/11/2017 18:47:15
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