advice on debugging attempt to read or write protected memory exception with winforms

Question

Some background, this application is a printing application that runs within REvit Structure, an Autodesk program. Its a .net add-in.

I have been plagued with these sort of exceptions that pop up intermittently and it is really frustrating. How can I go about debugging these?

Generally it is advised multi-threading is not used in Revit add-ins, and all I'm doing in this particular instance is reading some information from Revit and then showing a dialog box if there was some information missing. I don't know why that causes AccessVioldationExceptions

Unhandled exception!: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.; StackTrace:    at CCmdUI.DoUpdate(CCmdUI* , CCmdTarget* , Int32 )
   at CTestCmdUI.computeEnabled(CTestCmdUI* , CCmdTarget* pTarget)
   at UIFrameworkServices.CommandHandlerService.canExecute(String strName)
   at UIFramework.CommandUtility.CanExecute(RibbonCommandItem btn)
   at UIFramework.RibbonGlobalHandler.CanExecute(Object parameter)
   at Autodesk.Windows.InternalCommands.CanExecuteGenericCommand(Object sender, CanExecuteRoutedEventArgs args)
   at System.Windows.Input.CommandBinding.OnCanExecute(Object sender, CanExecuteRoutedEventArgs e)
   at System.Windows.Input.CommandManager.FindCommandBinding(CommandBindingCollection commandBindings, Object sender, RoutedEventArgs e, ICommand command, Boolean execute)
   at System.Windows.Input.CommandManager.FindCommandBinding(Object sender, RoutedEventArgs e, ICommand command, Boolean execute)
   at System.Windows.Input.CommandManager.OnCanExecute(Object sender, CanExecuteRoutedEventArgs e)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
   at System.Windows.Input.RoutedCommand.CanExecuteImpl(Object parameter, IInputElement target, Boolean trusted, Boolean& continueRouting)
   at System.Windows.Input.RoutedCommand.CanExecute(Object parameter, IInputElement target)
   at MS.Internal.Commands.CommandHelpers.CanExecuteCommandSource(ICommandSource commandSource)
   at System.Windows.Controls.Primitives.ButtonBase.UpdateCanExecute()
   at System.Windows.Input.CommandManager.CallWeakReferenceHandlers(List`1 handlers)
   at System.Windows.Input.CommandManager.RaiseRequerySuggested(Object obj)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)
   at System.Windows.Threading.DispatcherOperation.InvokeImpl()
   at System.Threading.ExecutionContext.runTryCode(Object userData)
   at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Windows.Threading.DispatcherOperation.Invoke()
   at System.Windows.Threading.Dispatcher.ProcessQueue()
   at System.Windows.Threading.Dispatcher.WndProcHook(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, Boolean isSingleParameter)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)
   at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Boolean isSingleParameter)
   at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Form.ShowDialog(IWin32Window owner)
   at BWTools.ErrorDisplayer.DisplayErrorWithoutLogging(String message) in C:\devel\Revit Macros\2011\BWTools\ErrorDisplayer.cs:line 93
   at Plotting.Printers.FilePostProcessor.SetParameters(IDictionary`2 sheetLocations, ParameterGrabber grabber, FilePrintSettings settings) in C:\devel\Revit Macros\2011\PLT2\Plotting\Printers\FilePostProcessor.cs:line 277
   at Plotting.Printers.FilePostProcessor.ProcessSheets(IList`1 sheets, String extension, String finalLocation, ParameterGrabber grabber, FilePrintSettings settings) in C:\devel\Revit Macros\2011\PLT2\Plotting\Printers\FilePostProcessor.cs:line 37
   at Plotting.Printers.PdfPrinter.Print(PrintSelection selection, FilePrintSettings settings) in C:\devel\Revit Macros\2011\PLT2\Plotting\Printers\PdfPrinter.cs:line 68
   at Plotting.Printers.PdfPrinter.Print(PrintSelection selections, PrintSettings settings) in C:\devel\Revit Macros\2011\PLT2\Plotting\Printers\PdfPrinter.cs:line 112
   at Plotting.GuiControl.Print() in C:\devel\Revit Macros\2011\PLT2\Plotting\Gui\GuiControl.cs:line 148
   at Plotting.Gui.PrintingSplash.animationTimer_Tick(Object sender, EventArgs e) in C:\devel\Revit Macros\2011\PLT2\Plotting\Gui\PrintingSplash.xaml.cs:line 51
   at System.Windows.Forms.Timer.OnTick(EventArgs e)
   at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

So at the button you can see my FilePostProicessor.SetParameters method is where the messagebox is being raised from. But when that happens a bunch of other stuff goes on to do with Raising Events (part of windows forms code?) and then there is some Autodesk stuff at the top which I don't know about.

Also I noticed 'ExceptionWrapper.InternalRealCall' does that help me out at all, is there an actual exception somewhere I can see that is half useful for me?

Is there something I'm doing wrong here? My code is just single threaded looping through some stuff.

I realise this isn't a lot of information for you guys to say 'boom line 358 is your problem' but any advice on debugging/avoiding these types of errors would be helpful. I'm not doing anything unmanaged though I am using dsofile.dll to set some custom properties on a file, but that is a few lines of code above what I'm doing and I think its single threaded?

Answer 1

I think you might be seeing a re-entrancy problem here. The dialog pumps windows messages, which in this case is calling back into autodesk. Autodesk perhaps does not expect to be called back into--it may be in a bad state.

You might try creating a new thread for the dialog to run in.