Question

I have scenario where thread updates form’s control. I followed http://msdn.microsoft.com/en-us/library/ms171728.aspx to make it work, but I was not successful.

Program creates form control(list view), and a thread to fetch information from internet(stock quotes). Whenever user selects a known symbol from other form control, that would be added in listView, this intern adds to thread to fetch quotes from internet, and a delegate would be added to for that specific symbol, thread iterates through all the watch list symbols to fetch quotes from internet whenever there is change in price, thread calls registered delegate. In that delegate I am accessing listView elements, here I am facing problems thread inconsistent issues.

To solve this problem I followed the above mentioned link,
Approach-1) In the delegate I started background worker. Same problem
Approach-2) Main program creates background worker, this worker loops around a list to update in listView. Delegate adds new updated price to list on which background worker is looping. When background worker is accessing listView again thread inconsistent problems arise.

How to resolve this problem?

Answer 1

When background worker is accessing listView again thread inconsistent problems arise.

Yes. This is because it shouldn’t be done. A Background Worker only provides safe access to the UI the RunWorkerCompleted and ProgressChanged events. The DoWork event is still run in the non-UI thread. To access the UI from the non-UI thread, “marshal back” to the UI-thread using Control.Invoke or SynchronizationContext.Send (these should lead to further findings if used as keywords.)

Happy coding.