WPF global exception handler

Question

Sometimes  under not reproducible circumstances  my WPF application crashes without any message  The application simply close instantly   Where is the best place to implement the global Try Catch block  At least I have to implement a messagebox with   Sorry for the inconvenience

User · Answer

A complete solution is here  it s explained very nice with sample code  However  be careful that it does not close the application Add the line  Application Current Shutdown     to gracefully close the app

User · Answer

To supplement Thomas s answer  the Application class also has the DispatcherUnhandledException event that you can handle

User · Answer

In addition to the posts above  Application Current DispatcherUnhandledException  will not catch exceptions that are thrown from a thread other than the main thread  You have to catch those exceptions on the same thread they are thrown  But if you want to Handle them on your global exception handler you can pass it to the main thread   System Threading Thread t   new System Threading Thread      gt                try                                         this exception will not be catched by                Application DispatcherUnhandledException             throw new Exception  quot huh   quot                                      catch  Exception ex                          But we can handle it in the throwing thread               and pass it to the main thread wehre Application                DispatcherUnhandledException can handle it             System Windows Application Current Dispatcher Invoke                  System Windows Threading DispatcherPriority Normal                  new Action lt Exception gt   exc    gt                                              throw new Exception  quot Exception from another Thread quot   exc                           ex

User · Answer

I use the following code in my WPF apps to show a  Sorry for the inconvenience  dialog box whenever an unhandled exception occurs  It shows the exception message  and asks user whether they want to close the app or ignore the exception and continue  the latter case is convenient when a non-fatal exceptions occur and user can still normally continue to use the app    In App xaml add the Startup event handler    lt Application      Startup  Application Startup  gt    In App xaml cs code add Startup event handler function that will register the global application event handler   using System Windows Threading   private void Application Startup object sender  StartupEventArgs e           Global exception handling       Application Current DispatcherUnhandledException    new DispatcherUnhandledExceptionEventHandler AppDispatcherUnhandledException          void AppDispatcherUnhandledException object sender  DispatcherUnhandledExceptionEventArgs e              if DEBUG      In debug mode do not custom-handle the exception  let Visual Studio handle it      e Handled   false         else      ShowUnhandledException e              endif         void ShowUnhandledException DispatcherUnhandledExceptionEventArgs e        e Handled   true       string errorMessage   string Format  An application error occurred  nPlease check whether your data is correct and repeat the action  If this error occurs again there seems to be a more serious malfunction in the application  and you better close it  n nError   0  n nDo you want to continue  n if you click Yes you will continue with your work  if you click No the application will close         e Exception Message    e Exception InnerException    null     n         e Exception InnerException Message   null         if  MessageBox Show errorMessage   Application Error   MessageBoxButton YesNoCancel  MessageBoxImage Error     MessageBoxResult No              if  MessageBox Show  WARNING  The application will close  Any changes will not be saved  nDo you really want to close it     Close the application    MessageBoxButton YesNoCancel  MessageBoxImage Warning     MessageBoxResult Yes                Application Current Shutdown

User · Answer

You can trap unhandled exceptions at different levels    AppDomain CurrentDomain UnhandledException From all threads in the AppDomain  Dispatcher UnhandledException From a single specific UI dispatcher thread  Application Current DispatcherUnhandledException From the main UI dispatcher thread in your WPF application  TaskScheduler UnobservedTaskException from within each AppDomain that uses a task scheduler for asynchronous operations    You should consider what level you need to trap unhandled exceptions at   Deciding between  2 and  3 depends upon whether you re using more than one WPF thread   This is quite an exotic situation and if you re unsure whether you are or not  then it s most likely that you re not

User · Answer

As mentioned above      Application Current DispatcherUnhandledException will not catch   exceptions that are thrown from another thread then the main thread    That actual depend on how the thread was created  One case that is not handled by Application Current DispatcherUnhandledException is System Windows Forms Timer for which Application ThreadException can be used to handle these if you run Forms on other threads than the main thread you will need to set Application ThreadException from each such thread

User · Answer

Best answer is probably https   stackoverflow com a 1472562 601990    Here is some code that shows how to use it    App xaml cs  public sealed partial class App       protected override void OnStartup StartupEventArgs e                   setting up the Dependency Injection container         var resolver   ResolverFactory Get                getting the ILogger or ILog interface         var logger   resolver Resolve lt ILogger gt             RegisterGlobalExceptionHandling logger               Bootstrapping Dependency Injection             injects ViewModel into MainWindow xaml            remember to remove the StartupUri attribute in App xaml         var mainWindow   resolver Resolve lt Pages MainWindow gt             mainWindow Show               private void RegisterGlobalExceptionHandling ILogger log                   this is the line you really want          AppDomain CurrentDomain UnhandledException                  sender  args    gt  CurrentDomainOnUnhandledException args  log               optional  hooking up some more handlers            remember that you need to hook up additional handlers when             logging from other dispatchers  shedulers  or applications          Application Dispatcher UnhandledException                  sender  args    gt  DispatcherOnUnhandledException args  log            Application Current DispatcherUnhandledException                 sender  args    gt  CurrentOnDispatcherUnhandledException args  log            TaskScheduler UnobservedTaskException                  sender  args    gt  TaskSchedulerOnUnobservedTaskException args  log              private static void TaskSchedulerOnUnobservedTaskException UnobservedTaskExceptionEventArgs args  ILogger log                log Error args Exception  args Exception Message           args SetObserved               private static void CurrentOnDispatcherUnhandledException DispatcherUnhandledExceptionEventArgs args  ILogger log                log Error args Exception  args Exception Message              args Handled   true             private static void DispatcherOnUnhandledException DispatcherUnhandledExceptionEventArgs args  ILogger log                log Error args Exception  args Exception Message              args Handled   true             private static void CurrentDomainOnUnhandledException UnhandledExceptionEventArgs args  ILogger log                var exception   args ExceptionObject as Exception          var terminatingMessage   args IsTerminating     The application is terminating     string Empty          var exceptionMessage   exception  Message     An unmanaged exception occured            var message   string Concat exceptionMessage  terminatingMessage           log Error exception  message

User · Answer

A quick example of code for Application Dispatcher UnhandledException   public App         this Dispatcher UnhandledException    OnDispatcherUnhandledException     void OnDispatcherUnhandledException object sender  System Windows Threading DispatcherUnhandledExceptionEventArgs e        string errorMessage   string Format  An unhandled exception occurred   0    e Exception Message       MessageBox Show errorMessage   Error   MessageBoxButton OK  MessageBoxImage Error          OR whatever you want like logging etc  MessageBox it s just example        for quick debugging etc      e Handled   true      I added this code in App xaml cs

User · Answer

You can handle the AppDomain UnhandledException event  EDIT  actually  this event is probably more adequate  Application DispatcherUnhandledException

[c#] WPF global exception handler

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