c# - Windows Form Embedded Progress Bar Background Worker -

i use progress bar in form having issues.

on form load, progress bar completes , list view populates icons "connected" devices.

when try select index in list of network adapters, progress bar , list view clear exception thrown , nothing happens in gui.

exception thrown: 'system.invalidoperationexception' in system.windows.forms.dll

i'm assuming threading issue have no idea.

here codes, or advice appreciated.

using system; using system.collections.generic; using system.componentmodel; using system.data; using system.drawing; using system.linq; using system.net.networkinformation; using system.text; using system.threading.tasks; using system.windows.forms;  namespace windowsformsapplication1 {     public partial class connectdialog : form     {         backgroundworker bkgndworker = null;         dictionary<string, int> dictionary = new dictionary<string, int>();         imagelist deviceimagelist = new imagelist();          public connectdialog()         {             initializecomponent();                }          public connectdialog(list<string> ipaddr)         {             initializecomponent();             cbonetworkadapter.items.addrange(ipaddr.toarray());             cbonetworkadapter.selectedindex = 0;         }          private void connectdialog_load(object sender, eventargs e)         {             bitmap devimage = properties.resources.devicon;             deviceimagelist.images.add(devimage);             deviceimagelist.imagesize = new size(30, 30);         }          private void cbonetworkadapter_selectedindexchanged(object sender, eventargs e)         {             startworking();         }          private void startworking()         {             prgbarconnect.value = 0;             dictionary.clear();             lstvwdevids.clear();             bkgndworker = new backgroundworker();              bkgndworker.dowork += new doworkeventhandler(bkgndworker_dowork);             bkgndworker.progresschanged += new progresschangedeventhandler(bkgndworker_progresschanged);             bkgndworker.runworkercompleted += new runworkercompletedeventhandler(bkgndworker_runworkercompleted);             bkgndworker.workerreportsprogress = true;             bkgndworker.runworkerasync();             bkgndworker.dispose();         }          private void bkgndworker_dowork(object sender, doworkeventargs e)         {             int numdevs = 0;             switch (cbonetworkadapter.selectedindex)             {                 case 0:                     numdevs = 4;                     break;                 case 1:                     numdevs = 1;                     break;                 case 2:                     numdevs = 10;                     break;             }             populateimages(numdevs);         }          void bkgndworker_progresschanged(object sender, progresschangedeventargs e)         {             prgbarconnect.value = e.progresspercentage;         }          void bkgndworker_runworkercompleted(object sender, runworkercompletedeventargs e)         {             foreach (keyvaluepair<string, int> entry in dictionary)             {                 listviewitem lstviewdevimage = new listviewitem(entry.key, entry.value);                 lstvwdevids.items.add(lstviewdevimage);             }              if (lstvwdevids.selecteditems.count > 0)                 console.writeline(string.format("device id: {0}", lstvwdevids.items.indexof(lstvwdevids.selecteditems[0])));              lstvwdevids.largeimagelist = deviceimagelist;         }          private void populateimages(int numdevs)         {             (int = 1; <= numdevs; i++)             {                 system.threading.thread.sleep(100);                 int percents = (i * 100) / numdevs;                  string lstvwitemdesc = string.format("dev {0}", - 1);                 dictionary.add(lstvwitemdesc, deviceimagelist.images.count - 1);                 bkgndworker.reportprogress(percents, i);             }         }     } } 

don't call dispose on backgroundworker want have running. instead:

// if have instance of backgroundworker ... // cancel , dispose 1 if (bkgndworker !=null)  {     // in case want end dowork nicely     bkgndworker.cancelasync();      bkgndworker.dispose(); }  // start again bkgndworker = new backgroundworker();  bkgndworker.dowork += new doworkeventhandler(bkgndworker_dowork); bkgndworker.progresschanged += new progresschangedeventhandler(bkgndworker_progresschanged); bkgndworker.runworkercompleted += new runworkercompletedeventhandler(bkgndworker_runworkercompleted); bkgndworker.workerreportsprogress = true; bkgndworker.runworkerasync(); // removed call dispose 

you might want implement dispose on form same cleanup of backgroundworker instance.