更新到EF 6.0.0-alpha后，无法使用EF迁移更新数据库

Question

将我的实体框架更新为6.0.0-alpha1版本后，我无法更新数据库。 这是我得到的错误：

PM> update-database -verbose 
Using StartUp project 'DataCenter'. 
Using NuGet project 'DataCenter.Domain'. 
Specify the '-Verbose' flag to view the SQL statements being applied to the target database. 
Target database is: 'datacenter' (DataSource: ., Provider: System.Data.SqlClient, Origin: Configuration). 
Upgrading history table. 
ALTER TABLE [dbo].[__MigrationHistory] ADD [ContextKey] [nvarchar](512) NOT NULL DEFAULT 'DataCenter.Domain.Migrations.Configuration' 
ALTER TABLE [dbo].[__MigrationHistory] DROP CONSTRAINT [PK_dbo.__MigrationHistory] 
System.Data.SqlClient.SqlException (0x80131904): 'PK_dbo.__MigrationHistory' is not a constraint. 
Could not drop constraint. See previous 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) 
    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.Migrations.DbMigrator.ExecuteSql(DbTransaction transaction, MigrationStatement migrationStatement) 
    at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.ExecuteSql(DbTransaction transaction, MigrationStatement migrationStatement) 
    at System.Data.Entity.Migrations.DbMigrator.ExecuteStatements(IEnumerable`1 migrationStatements) 
    at System.Data.Entity.Migrations.Infrastructure.MigratorBase.ExecuteStatements(IEnumerable`1 migrationStatements) 
    at System.Data.Entity.Migrations.DbMigrator.UpgradeHistory(IEnumerable`1 upgradeOperations) 
    at System.Data.Entity.Migrations.Infrastructure.MigratorLoggingDecorator.UpgradeHistory(IEnumerable`1 upgradeOperations) 
    at System.Data.Entity.Migrations.DbMigrator.Update(String targetMigration) 
    at System.Data.Entity.Migrations.Infrastructure.MigratorBase.Update(String targetMigration) 
    at System.Data.Entity.Migrations.Design.ToolingFacade.UpdateRunner.RunCore() 
    at System.Data.Entity.Migrations.Design.ToolingFacade.BaseRunner.Run() 
ClientConnectionId:eda1a366-d3c8-44de-8cc9-8f64e2511b4e 
'PK_dbo.__MigrationHistory' is not a constraint. 
Could not drop constraint. See previous errors. 

什么的原因呢？我查询了'PK_dbo .__ MigrationHistory'的sysobjects表，但那不存在。 有什么想法？

在此先感谢。

Answer 1

好的。我找到了解决方案。 看来，EF期望__MigrationHistory表的主键约束具有名称PK_dbo.__MigrationHistory。但它是PK___MigrationHistory。

所以下面的sql语句将做的伎俩。

ALTER TABLE __MigrationHistory 
drop CONSTRAINT PK___MigrationHistory 
ALTER TABLE __MigrationHistory 
ADD CONSTRAINT [PK_dbo.__MigrationHistory] PRIMARY KEY (MigrationId) 

之后我已经使用update-database没有错误。