c# - Create labels in form and update them from background threads -

i have number of background threads (in case 5) generated code below:

 progress prog = new progress();  foreach (var questionlang in questionslangconstants.questionlangs.values)  {   threadpool.queueuserworkitem(    delegate    {     qrepo.uploadquestions(qworkbook.worksheets[questionlang.qsheet], questionlang, prog);    });  }  prog.show(); 

progress form has following code in it.

private delegate label addnewlabel(); private delegate void changelabeltext(label lbl, string text);       public label addnewlabel()     {         if (this.invokerequired)         {             addnewlabel adl = new addnewlabel(addnewlabel);             this.invoke(adl);             return new label();         }         else         {             label lbl = new label();              this.controls.add(lbl);             return lbl;         }     }      public void changelabeltext(label lbl, string text)     {         if (this.invokerequired)         {             changelabeltext clt = new changelabeltext(changelabeltext);             this.invoke(clt, new object[] { lbl, text });          }         else         {              lbl.text = text;          }     } 

and uploadquestions function reads , excel file , uses

 label lbl = prog.addnewlabel();  while (questionnum != "")  {     //code here     prog.changelabeltext(lbl, questionnum);    //code increment questionnum   } 

i expect 5 labels created , updated number of rows in excel nothing happens. labels not updated created. (even on over other).

i think in method "public label addnewlabel()" in if statement after invoking delegate, returning new label , not original label created in else statement. not sure if problem though.

edit:

instead of "this.invoke(adl);" try "return (this.invoke(adl) label);" , remove "return new label();" statement.