C# Language BackgroundWorker

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  • bgWorker.CancellationPending //returns whether the bgWorker was cancelled during its operation

  • bgWorker.IsBusy //returns true if the bgWorker is in the middle of an operation

  • bgWorker.ReportProgress(int x) //Reports a change in progress. Raises the "ProgressChanged" event

  • bgWorker.RunWorkerAsync() //Starts the BackgroundWorker by raising the "DoWork" event

  • bgWorker.CancelAsync() //instructs the BackgroundWorker to stop after the completion of a task.


Performing long-running operations within the UI thread can cause your application to become unresponsive, appearing to the user that it has stopped working. It is preferred that these tasks be run on a background thread. Once complete, the UI can be updated.

Making changes to the UI during the BackgroundWorker's operation requires invoking the changes to the UI thread, typically by using the Control.Invoke method on the control you are updating. Neglecting to do so will cause your program to throw an exception.

The BackgroundWorker is typically only used in Windows Forms applications. In WPF applications, Tasks are used to offload work onto background threads (possibly in combination with async/await). Marshalling updates onto the UI thread is typically done automatically, when the property being updated implements INotifyPropertyChanged, or manually by using the UI thread's Dispatcher.

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