How can I wait for BackgroundWorker?

Question

I have a method Foo() , which creates and runs a BackgroundWorker .
RunWorkerCompleted , ProgressChanged etc. are handled inside Foo() .

My main thread calls MyObject.Foo() .
Right after calling MyObject.Foo() main thread calls MyObject.DoSthWithFooData() .

Main Thread doesn't know anything about the BackgroundWorker inside MyObject.Foo() .

How can I force main thread to wait until BackgroundWorker has finished its work?

DoSthWithFooData() must be called when the BackgroundWorker in MyObject.Foo() has finished its job.

Answer 1

You don't want the main thread to wait for the BackgroundWorker. That would cause your GUI to become unresponsive - not a good user experience. The whole point of using the BackgroundWorker in the first place is to avoid blocking the main thread. Instead you should register an event handler for the background worker's RunWorkerCompleted event. The code in the event handler will be run when the background task completes.

If you want to prevent users from interacting with the program while the background task is running then:

• Disable the relevant controls when you start the BackgroundWorker.
• Re-enable them again in the RunWorkerCompleted event handler.

Answer 2

将DoSthWithFooData放入RunWorkerCompleted事件中

Answer 3

You have two choices:

1. You can remove the BackgroundWorker entirely and just execute your code synchronously. If you're going to force the code to wait on the BackgroundWorker to finish anyway, then that's essentially what you're doing. This is not the best option, assuming that the next is practical for you.
2. Move the logic that would ordinarily follow the call to MyObject.Foo() into the RunWorkerCompleted event handler. This is preferred, as it will maintain the "background" element of the work and the UI will remain responsive.

Answer 4

Give Foo() a parameter a callbacb Action delegate that is called when foo is done And then you can Use MenualResetEvent to wait for Foo to finish.

when Action delegate is called signal ManualReset event