c# - Passing collection from backgroundworker DoWork to backgroundworker Completed and perform a foreach -

my goal here is:

• user types full or partial computername combobox
• button click event starts background worker passing computername dowork method
• dowork method searches activedirectory computername , passes collection workercompleted method
• workercompleted method adds each computername combobox items.

my error @ foreach loop in backgroundworker_runworkercompleted method.

• "foreach statement cannot operate on variables of type 'object' because 'object' not contain public definition 'getenumerator'"

if messagebox.show(results.first().tostring()); in dowork method, can view first computername in collection. (forgive me if collection correct term)

if messagebox.show(e.result.tostring()); in dowork , workercompleted method, this:

• "system.directoryservices.accountmanagement.principalsearchresult`1[system.directoryservices.accountmanagement.principal]"

i picked c# month ago , i'm coming powershell apologize in advance if i'm using wrong vocabulary. new me.

any guidance on appreciated!

    private void button1_click(object sender, eventargs e)     {         //saves computername entered user pass dowork method         string pcname = combobox1.text;          //start background thread passing computer dowork method         backgroundworker1.runworkerasync(pcname);     }      private void backgroundworker1_dowork(object sender, doworkeventargs e)     {                          using (principalcontext ctx = new principalcontext(contexttype.domain))         {             //setup filter             computerprincipal computer = new computerprincipal(ctx);             computer.name = "*" + e.argument + "*";              //search pc             principalsearcher ps = new principalsearcher();             ps.queryfilter = computer;              //get results             principalsearchresult<principal> results = ps.findall();              //results passed runworkercompleted             e.result = results;                         }     }      private void backgroundworker1_runworkercompleted(object sender, runworkercompletedeventargs e)     {         //add each computername combobox         foreach (object pc in e.result) // <--------------- error here!         {             combobox1.items.add(pc.tostring());         }                                 } } 

you have cast e.result in completed handler object principalsearchresult<principal> in order iterate through it.

private void backgroundworker1_runworkercompleted(object sender, runworkercompletedeventargs e) {     //add each computername combobox     principalsearchresult<principal> results = (principalsearchresult<principal>)e.result;     foreach (principal pc in results)     {         combobox1.items.add(pc.tostring());     }                             } 

edit:

principalsearcher can't used in background worker, because it's uses of com component requires single-threaded apartment (sta). background worker thread runs in multithreaded apartment (mta). apartmentstate can set using thread.setapartmentstate, must called before thread starts (so can't used change apartmentstate of backgroundworker's working thread).