wns - UWP PushNotificationTrigger won't trigger background task -

i trying develop windows 10 uwp app has background task triggered raw pushnotification trigger. test, have handler on app see if raw notification pushing , worked. here code snippets:

    pushnotificationchannel _channel = null;      private async void appinit()     {         _channel = await common.wnshelper.getchannelasync();         if (_channel != null)         {             _channel.pushnotificationreceived += _channel_pushnotificationreceived;         }         await installpositionbackgroundtask();       }      private  async void _channel_pushnotificationreceived(pushnotificationchannel sender, pushnotificationreceivedeventargs args)     {         if (args.notificationtype == pushnotificationtype.raw)         {             common.generalhelper.sendtoast("at app positionbackgroundtask");         }     }      private async task installpositionbackgroundtask()     {         var taskname = "positionbackgroundtask";          foreach (var tsk in backgroundtaskregistration.alltasks)         {             if (tsk.value.name == taskname)             {                 tsk.value.unregister(true);             }         }          var cost = backgroundworkcost.currentbackgroundworkcost;         if (cost == backgroundworkcostvalue.high)         {             return;         }          var allowed = await backgroundexecutionmanager.requestaccessasync();         if (allowed == backgroundaccessstatus.allowedsubjecttosystempolicy             || allowed == backgroundaccessstatus.alwaysallowed)         {             var builder = new backgroundtaskbuilder();              builder.name = nameof(positionbackgroundtask.positionbackgroundtask);             builder.cancelonconditionloss = false;             builder.taskentrypoint = typeof(positionbackgroundtask.positionbackgroundtask).fullname;             builder.settrigger(new pushnotificationtrigger());             backgroundtaskregistration task = builder.register();             task.completed += new backgroundtaskcompletedeventhandler(oncompleted);              common.generalhelper.sendtoast("position task installed. " + system.datetime.now.tostring());         }     }     private async void button_click(object sender, routedeventargs e)     {         // send         var response = await common.wnshelper.pushrawasync<common.rawrequest>(_channel.uri, new rawrequest() { requesttype = rawrequesttype.requestposition, fromdeviceid = _alldevices[0].d_id }, null);     } 

here's background task

namespace positionbackgroundtask  {     public sealed class positionbackgroundtask     {          backgroundtaskdeferral _deferral;         public async void run(ibackgroundtaskinstance taskinstance)         {             common.generalhelper.sendtoast("at positionbackgroundtask");              var cancel = new system.threading.cancellationtokensource();             taskinstance.canceled += (s, e) =>             {                 cancel.cancel();                 cancel.dispose();             };              _deferral = taskinstance.getdeferral();             try             {                 rawnotification notification = (rawnotification)taskinstance.triggerdetails;                 //:                 //:                 //:             }                         {                 _deferral.complete();             }         }     } } 

here's manifest

<extension category="windows.backgroundtasks" entrypoint="positionbackgroundtask.positionbackgroundtask">   <backgroundtasks>     <task type="pushnotification" />   </backgroundtasks> </extension> 

here's code send raw notification

 public static async task<httpresponsemessage> pushrawasync<t>(string channeluri, rawrequest request, t rawdata) {     // app authorization     string appdatasecret = myappsecret;     uri requesturi = new uri(@"https://login.live.com/accesstoken.srf");       var client = new system.net.http.httpclient();     system.net.http.httpresponsemessage response = await client.postasync(requesturi, new stringcontent(appdatasecret, system.text.encoding.utf8, "application/x-www-form-urlencoded"));     string responjsontext = await response.content.readasstringasync();      wmntoken token = jsonconvert.deserializeobject<wmntoken>(responjsontext);      string requeststr = jsonconvert.serializeobject(request) + ";" + jsonconvert.serializeobject(rawdata);     var content = new streamcontent(new memorystream(encoding.utf8.getbytes(requeststr)));      client.defaultrequestheaders.authorization = new system.net.http.headers.authenticationheadervalue(token.token_type, token.access_token);     client.defaultrequestheaders.add("x-wns-type", "wns/raw");      response = await client.postasync(channeluri, content);     return response; } 

the app received notification background task never. did wrong?

more info: looks push notification hitting box got error in event log

activation of app 45737myname.testpushnotificationpartofemail_4rhf8erfmecqa!app windows.backgroundtasks contract failed error: no such interface supported. 

and turns out didn't subclass ibackgroundtask should this

 public sealed class positionbackgroundtask : ibackgroundtask 

background tasks need subclass of ibackgroundtask

public sealed class positionbackgroundtask : ibackgroundtask