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c#winformsbackgroundworker
dylanmensaert
dylanmensaert

Reputation: 1749

Why does the BackgroundWorker's ProgressChanged event work without calling RunWorkerAsync?

I have a question regarding the BackgroundWorker. I can call the ProgressChanged event without having started the thread with RunWorkerAsync.

I don't understand why this works. How can it notify the original thread if the new thread didn't even start yet?

This seems to work regardless, since it updates the GUI without a problem, which wasn't like this before I implemented the BackgroundWorker.

Upvotes: 2

Views: 725

Answers (1)

Matthew Watson
Matthew Watson

Reputation: 109862

Calling ReportProgressChanged() will always raise the ProgressChanged event regardless of which thread it was called from.

Inside the inplementation of ReportProgressChanged() is a mechanism which raises the event on the UI thread if it wasn't called from the UI thread. If ReportProgressChanged() is being called from the UI thread, then it just raises the event without needing to do that extra marshalling.

Upvotes: 7

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