ObjectContext.SaveChanges（）失败，SQL CE

Question

我创建一个使用SQL CE作为其数据存储模型，第一实体框架4应用程序。一切都很好，直到我打电话ObjectContext.SaveChanges()将更改保存到模型中的实体。在该点，调用SaveChanges（）抛出一个System.Data.UpdateException，条件是如下的内部异常消息：

服务器生成的密钥和服务器生成的值不是由SQL Server精简支持。

我完全被这个消息感到不解。任何想法是怎么回事，如何解决？谢谢。

这里是异常转储：

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

我想我已经找到了我的答案。当与实体框架使用，SQL CE不支持自动生成主键：

Entity Framework: No support for server-generated keys and server-generated values

链接的线程解释了为什么自动生成主键不支持。

编辑：我没有找到一个解决办法，这是记录here。

Answer 2

我的解决方法是完全抛弃EF和使用LINQ到SQL语句。我愉快地使用标识字段因为没有在所有的任何问题，一个主键。

如果试图在此VS2010你会击中另一个疑难杂症 - VS会说，L2S不支持SQL精简，但实际上它的作用。打开Visual Studio命令提示符，然后运行：

sqlmetal filename.sdf /dbml:filename.dbml

然后dbml的文件添加到该项目作为现有项目。