c# - Getting Dispatcher in Lockscreen (Assigned-access) mode in a timer callback -


i'm having trouble getting dispatcher using getcurrentview() method. stated on msdn should using coreapplication.getcurrentview() if app running in assigned access mode.

https://msdn.microsoft.com/windows/hardware/drivers/partnerapps/create-a-kiosk-app-for-assigned-access

however getcurrentview() causes exception when used in timer callback.

anybody have suggestion how can work in assigned access mode? here's code comments does, , doesn't work.

sealed partial class app : application {     private timer timer;      public app()     {         this.initializecomponent();     }      protected override void onlaunched(launchactivatedeventargs e)     {         try         {             isassignedaccess = lockapplicationhost.getforcurrentview() != null;         }         catch         {             isassignedaccess = false;         }          // works fine         ontimerasync();          // timer callback ontimerasync() doesn't work (see below)         this.timer = new timer((e2) => { ontimerasync(); }, null, (int)timespan.fromseconds(5).totalmilliseconds,             (int)timespan.fromseconds(5).totalmilliseconds);      }      private async void ontimerasync()     {         if (app.isassignedaccess)         {             // causes app crash in assigned access mode             await coreapplication.getcurrentview().dispatcher.runasync(coredispatcherpriority.normal, () => { /* void */ });         }         else         {             // works fine in desktop mode, doesn't work in assigned access mode (lockscreen app)             await coreapplication.mainview.corewindow.dispatcher.runasync(coredispatcherpriority.normal, () => { /* void */ });              // line below causes app crash when called timer callback, works fine when called directly onlaunched();             var curview = coreapplication.getcurrentview();             /*                 * exception details when called timer callback                 * exception thrown: 'system.runtime.interopservices.comexception' in lockscreentest.exe                 * winrt information: kan element niet vinden. (translated: cannot find element)                 */              var curdispatch = curview.dispatcher;             await curdispatch.runasync(coredispatcherpriority.normal, () => { /* void */ });         }     }      public static bool isassignedaccess { get; private set; } }

ps. example timer, i'm using nfc/smartcard , other async libraries have similar problems on event triggers.

i solved issue using dispatcherhelper class mvvmlight replace getcurrentview() method.

this class sets static reference dispatcher upon app startup later used wherever need (e.g. -thought- getcurrentview() supposed do)

see (excellent) article more details:

http://msdn.microsoft.com/en-us/magazine/dn630646.aspx?f=255&mspperror=-2147217396


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