在ASP.Net vNext站点中，为什么启动时会出现与迁移相关的exception？

我没有定义迁移，但在很长的超时后，我仍然看到启动时__MigrationHistory表的exception。

我的初始化代码如下所示：

 public void ConfigureServices(IServiceCollection services) { services.AddMvc(); services.AddEntityFramework() .AddSqlServer() .AddDbContext(options => options.UseSqlServer(Configuration.Get("ConnectionString"))); } public void Configure(IApplicationBuilder app) { var loggerFactory = (ILoggerFactory)app.ApplicationServices.GetService(typeof(ILoggerFactory)); loggerFactory.AddProvider( new DiagnosticsLoggerProvider( new SourceSwitch("SourceSwitch", "Information"), new ConsoleTraceListener())); Trace.WriteLine("Configure."); app.UseDefaultFiles(); app.UseStaticFiles(); app.UseErrorPage(); app.UseDatabaseErrorPage(); app.UseMvc(routes => { routes.MapRoute( name: "default", template: "{controller}/{action}/{id?}", defaults: new { controller = "Home", action = "Index" }); }); } 

例外：

 Microsoft.Data.Entity.Query.EntityQueryExecutor Error: 0 : An exception occurred in the data store while iterating the results of a query. System.Data.SqlClient.SqlException (0x80131904): Invalid object name '__MigrationHistory'. 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.SqlDataReader.TryConsumeMetaData() at System.Data.SqlClient.SqlDataReader.get_MetaData() at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, SqlDataReader ds) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite) at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method) at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior) at System.Data.Common.DbCommand.ExecuteReader() at Microsoft.Data.Entity.Relational.Query.QueryingEnumerable`1.Enumerator.MoveNext() at System.Linq.Enumerable.d__8`2.MoveNext() at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext() at Microsoft.Data.Entity.Query.LinqOperatorProvider.d__1`2.MoveNext() at Microsoft.Data.Entity.Query.EntityQueryExecutor.EnumerableExceptionInterceptor`1.EnumeratorExceptionInterceptor.MoveNext() 

 private static bool _created = false; public ApplicationDbContext() { // Create the database and schema if it doesn't exist // This is a temporary workaround to create database until Entity Framework database migrations // are supported in ASP.NET 5 if (!_created) { Database.AsMigrationsEnabled().ApplyMigrations(); _created = true; } }