c# - WebBrowser control won't navigate to URL when the call is via a timer -

i'm trying make app in c# integrated system.windows.controls.webbrowser. need implement functionality make periodic checks user activity , if user not active timespan, redirect browser control home page.

below code snippet app. using system.timers.timer class periodically call checkuseractivity method, computes timespan , if timespan larger threshold, should redirect browser calling gohome method.

unfortunately, won't work , behaviour seems rather strange me. added logging see happens (see below). "should go away soon" message shows ok, after browser doesn't naviagte home page , second message after call navigate doesn't show up.

i absolutely no errors. works expected except call webbrowser's navigate method , call after vanished somehow.

i suspect problem might have threads, have little experience c# have absolutely no idea problem might here.

i tried rewrite code using system.threading.tasks.task library in same way mentioned @ http://stackoverflow.com/questions/8267298/how-to-start-a-long-running-process-in-a-separate-thread (sry link inside code block - not enough reputation :d ). put checking code inside infinite loop runs long running task , thread sleeps 2 seconds, ran same problem.

thanks advice. here code snippet (it should work standalone project):

xaml:

<window x:class="timertest.mainwindow"         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"         title="mainwindow" height="800" width="800">     <grid>         <webbrowser x:name="webbrowser"                              loadcompleted="webbrowser_loadcompleted"                 ></webbrowser>     </grid> </window> 

c#:

using system; using system.collections.generic; using system.linq; using system.text; using system.threading.tasks; using system.timers; using system.windows; using system.windows.controls; using system.windows.data; using system.windows.documents; using system.windows.input; using system.windows.media; using system.windows.media.imaging; using system.windows.navigation; using system.windows.shapes;  namespace timertest {     /// <summary>     /// interaction logic mainwindow.xaml     /// </summary>     public partial class mainwindow : window     {          private uri uri_home;         private timer timer;         private uri uri_last;         private datetime lastused;          public mainwindow()         {             uri_home = new uri("http://example.com/", urikind.relativeorabsolute);             uri_last = uri_home;              initializecomponent();              webbrowser.navigate(uri_home);              // create timer 2 second interval.             timer = new timer(2000);             // hook elapsed event timer.              timer.elapsed += checkuseractivity;             timer.autoreset = true;             timer.enabled = false;             lastused = datetime.now;         }          private void gohome()         {             //system.windows.forms.methodinvoker update = delegate()             //{             webbrowser.navigate(uri_home);             //};             //webbrowser.invoke(update);         }          private void logmessage(string msg)         {             datetime = datetime.now;             console.writeline(now.tostring() + ": " + msg);         }          private void checkuseractivity(object source, elapsedeventargs e)         {             logmessage("entered checkuseractivity handler");             datetime = datetime.now;             timespan timespan = - lastused;             logmessage("timespan " + timespan.seconds.tostring());             if (timespan.seconds > 5 && uri_home != uri_last)             {                 timer.enabled = false;                 logmessage("timer disabled.");                 logmessage("will go away soon.");                 gohome();                 logmessage("should have gone home");             }         }          private void webbrowser_loadcompleted(object sender, navigationeventargs e)         {             webbrowser browser = (webbrowser)sender;             uri uri_navigated = e.uri;             uri_last = uri_navigated;             logmessage("webbrowser loadcompleted event triggered. loadcompleted uri (saved uri_last): " + uri_navigated.absoluteuri);             logmessage("timer enabled status: " + timer.enabled.tostring());             lastused = datetime.now;             timer.enabled = true;             logmessage("timer enabled (end of loadcompleted handler).");         }     } } 

here output of 1 session:

11.9.2014 8:10:01: webbrowser loadcompleted event triggered. loadcompleted uri (saved uri_last): http://example.com/ 11.9.2014 8:10:01: timer enabled status: false 11.9.2014 8:10:01: timer enabled (end of loadcompleted handler). 11.9.2014 8:10:03: entered checkuseractivity handler 11.9.2014 8:10:03: timespan 2 11.9.2014 8:10:05: entered checkuseractivity handler 11.9.2014 8:10:05: timespan 4 11.9.2014 8:10:07: entered checkuseractivity handler 11.9.2014 8:10:07: timespan 6 11.9.2014 8:10:09: entered checkuseractivity handler 11.9.2014 8:10:09: timespan 8 11.9.2014 8:10:11: entered checkuseractivity handler 11.9.2014 8:10:11: timespan 10 11.9.2014 8:10:13: entered checkuseractivity handler 11.9.2014 8:10:13: timespan 12 11.9.2014 8:10:15: entered checkuseractivity handler 11.9.2014 8:10:15: timespan 14 11.9.2014 8:10:17: entered checkuseractivity handler 11.9.2014 8:10:17: timespan 16 11.9.2014 8:10:19: entered checkuseractivity handler 11.9.2014 8:10:19: timespan 18 11.9.2014 8:10:21: entered checkuseractivity handler 11.9.2014 8:10:21: timespan 20 11.9.2014 8:10:23: entered checkuseractivity handler 11.9.2014 8:10:23: timespan 22 11.9.2014 8:10:25: entered checkuseractivity handler 11.9.2014 8:10:25: timespan 24 11.9.2014 8:10:27: entered checkuseractivity handler 11.9.2014 8:10:27: timespan 26 11.9.2014 8:10:29: entered checkuseractivity handler 11.9.2014 8:10:29: timespan 28 11.9.2014 8:10:30: webbrowser loadcompleted event triggered. loadcompleted uri (saved uri_last): http://www.iana.org/domains/reserved 11.9.2014 8:10:30: timer enabled status: true 11.9.2014 8:10:30: timer enabled (end of loadcompleted handler). 11.9.2014 8:10:31: entered checkuseractivity handler 11.9.2014 8:10:31: timespan 1 11.9.2014 8:10:33: entered checkuseractivity handler 11.9.2014 8:10:33: timespan 3 11.9.2014 8:10:35: entered checkuseractivity handler 11.9.2014 8:10:35: timespan 5 11.9.2014 8:10:37: entered checkuseractivity handler 11.9.2014 8:10:37: timespan 7 11.9.2014 8:10:37: timer disabled. 11.9.2014 8:10:37: go away soon. 

the browser navigates homepage (example.com) after started. timer disabled, gets enabled @ end of loadcompleted handler. user lingers bit , clicks link on page. loadcompleted triggered (timer remains enabled, because didn't have change url yet). user lingers again, time not on homepage, condition inside checkuseractivity true after while, timer disabled , browser should navigate home page, nothing happens... sad story :(

it threading problem - if replace gohome method following one, starts working.

enjoy :)

private void gohome() {         dispatcher.invokeasync(() => { webbrowser.navigate(uri_home); }); }