ObjectContext.SaveChanges () non riesce con SQL CE

Question

Sto creando un Entity Framework 4 app modello prima che utilizza SQL CE come il suo archivio di dati. Tutto va bene fino a quando io chiamo ObjectContext.SaveChanges() per salvare le modifiche alle entità nel modello. A quel punto, SaveChanges () tiri uno System.Data.UpdateException, con un messaggio di eccezione interna che recita come segue:

chiavi generate dal server ed i valori generati dal server non sono supportate da SQL Server Compact.

Sono completamente perplesso da questo messaggio. Qualche idea di cosa sta succedendo e come risolvere il problema? Grazie.

Ecco la discarica Eccezione:

System.Data.UpdateException was unhandled
  Message=An error occurred while updating the entries. See the inner exception for details.
  Source=System.Data.Entity
  StackTrace:
       at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter)
       at System.Data.EntityClient.EntityAdapter.Update(IEntityStateManager entityCache)
       at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options)
       at System.Data.Objects.ObjectContext.SaveChanges()
       at FsDocumentationBuilder.ViewModel.Commands.SaveFileCommand.Execute(Object parameter) in D:\Users\dcveeneman\Documents\Visual Studio 2010\Projects\FsDocumentationBuilder\FsDocumentationBuilder\ViewModel\Commands\SaveFileCommand.cs:line 68
       at MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(ICommandSource commandSource, Boolean userInitiated)
       at System.Windows.Controls.Primitives.ButtonBase.OnClick()
       at System.Windows.Controls.Button.OnClick()
       at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
       at System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e)
       at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
       at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
       at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
       at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
       at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
       at System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e)
       at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
       at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
       at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
       at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
       at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
       at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
       at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
       at System.Windows.Input.InputManager.ProcessStagingArea()
       at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
       at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
       at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
       at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
       at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
       at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
       at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
       at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
       at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)
       at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
       at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
       at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
       at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
       at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
       at System.Windows.Threading.Dispatcher.Run()
       at System.Windows.Application.RunDispatcher(Object ignore)
       at System.Windows.Application.RunInternal(Window window)
       at System.Windows.Application.Run(Window window)
       at System.Windows.Application.Run()
       at FsDocumentationBuilder.App.Main() in D:\Users\dcveeneman\Documents\Visual Studio 2010\Projects\FsDocumentationBuilder\FsDocumentationBuilder\obj\x86\Debug\App.g.cs:line 50
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: System.Data.EntityCommandCompilationException
       Message=An error occurred while preparing the command definition. See the inner exception for details.
       Source=System.Data.Entity
       StackTrace:
            at System.Data.Mapping.Update.Internal.UpdateTranslator.CreateCommand(DbModificationCommandTree commandTree)
            at System.Data.Mapping.Update.Internal.DynamicUpdateCommand.CreateCommand(UpdateTranslator translator, Dictionary`2 identifierValues)
            at System.Data.Mapping.Update.Internal.DynamicUpdateCommand.Execute(UpdateTranslator translator, EntityConnection connection, Dictionary`2 identifierValues, List`1 generatedValues)
            at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter)
       InnerException: System.NotSupportedException
            Message=Server-generated keys and server-generated values are not supported by SQL Server Compact.
            Source=System.Data.SqlServerCe.Entity
            StackTrace:
                 at System.Data.SqlServerCe.SqlGen.DmlSqlGenerator.GenerateReturningSql(StringBuilder commandText, DbModificationCommandTree tree, ExpressionTranslator translator, DbExpression returning)
                 at System.Data.SqlServerCe.SqlGen.DmlSqlGenerator.GenerateInsertSql(DbInsertCommandTree tree, List`1& parameters, Boolean isLocalProvider)
                 at System.Data.SqlServerCe.SqlGen.SqlGenerator.GenerateSql(DbCommandTree tree, List`1& parameters, CommandType& commandType, Boolean isLocalProvider)
                 at System.Data.SqlServerCe.SqlCeProviderServices.CreateCommand(DbProviderManifest providerManifest, DbCommandTree commandTree)
                 at System.Data.SqlServerCe.SqlCeProviderServices.CreateDbCommandDefinition(DbProviderManifest providerManifest, DbCommandTree commandTree)
                 at System.Data.Common.DbProviderServices.CreateCommandDefinition(DbCommandTree commandTree)
                 at System.Data.Common.DbProviderServices.CreateCommand(DbCommandTree commandTree)
                 at System.Data.Mapping.Update.Internal.UpdateTranslator.CreateCommand(DbModificationCommandTree commandTree)
            InnerException: 

Answer 1

Credo di aver trovato la mia risposta. Quando viene utilizzato con Entity Framework, SQL CE non supporta chiavi primarie generati automaticamente:

Entity Framework : Nessun supporto per le chiavi generate dal server ed i valori generati dal server

Il filo collegato spiega perché le chiavi primarie generati automaticamente non sono supportati.

Edit: ho trovato una soluzione, che è documentata qui

.

Answer 2

La mia soluzione era quella di abbandonare EF del tutto e utilizzare LINQ to SQL. Sono felicemente utilizzando un campo di identità come chiave primaria, senza problemi a tutti.

Se si tenta questo in VS2010 ti ha colpito un altro Gotcha - VS dirà che L2S non supporta SQL Compact, ma in realtà lo fa. Aprire un prompt dei comandi di Visual Studio ed eseguire:

sqlmetal filename.sdf /dbml:filename.dbml

Quindi aggiungere il file dbml al progetto come un elemento esistente.