c# - Incorrect async/await working, Excel events in Excel Application Level Add-in -

i faced problem using async /await in add-in application, have custom task pane , user can download data it, there problems:

1. after awaited operation completed control not returned previous execution context. created example windows forms , paste same method awaiting , works fine - can use form controls after await operation, not in add-in, have call custom task pane invoke method. simple example:

   private void searchpanebutton_click(object sender, eventargs e) {     search(); }  private async void search() {     var searchtext = searchtextbox.text;     searchpanebutton.text = "loading…";     var data = await new dataserviceclient().getdataasync(searchtext);     this.invoke((methodinvoker)(() =>     {         searchpanebutton.text = "search";         toggleworkbookevents();     })); } 

2. in add-in need handle events - worksheet changed, worksheet activated/deactivated, these events disappear , isn't fired after await operation , have use "toggling"(remove+add) events after each await using. simple example:

   private void toggleworkbookevents() {     var excel = globals.bpnaddin.application;     //need ensure event not set twice     excel.sheetactivate -= checksheetfordata;     excel.sheetactivate += checksheetfordata;     if (excel.activeworkbook != null)     {         var activesheet = globals.bpnaddin.getactiveworksheet();         //need ensure event not set twice         activesheet.change -= worksheet_changed;         activesheet.change += worksheet_changed;     } } 

so maybe vsto framework can not support new features(like async await) of last versions .net framework?

this long-standing issue office plugins: don't provide synchronizationcontext.

as mention on blog, can work around ensuring have proper synchronizationcontext. bit hacky, works:

private async void searchpanebutton_click(object sender, eventargs e) {   if (synchronizationcontext.current == null)     synchronizationcontext.setsynchronizationcontext(new windowsformssynchronizationcontext());   await searchasync(); }  private async task searchasync() {   var searchtext = searchtextbox.text;   searchpanebutton.text = "loading…";   var data = await new dataserviceclient().getdataasync(searchtext);   searchpanebutton.text = "search";   toggleworkbookevents(); } 

as far "toggling events" problem goes, have no idea.