C# Language BackgroundWorker


See below for a simple example of how to use a BackgroundWorker object to perform time-intensive operations in a background thread.

You need to:

  1. Define a worker method that does the time-intensive work and call it from an event handler for the DoWork event of a BackgroundWorker.
  2. Start the execution with RunWorkerAsync. Any argument required by the worker method attached to DoWork can be passed in via the DoWorkEventArgs parameter to RunWorkerAsync.

In addition to the DoWork event the BackgroundWorker class also defines two events that should be used for interacting with the user interface. These are optional.

  • The RunWorkerCompleted event is triggered when the DoWork handlers have completed.
  • The ProgressChanged event is triggered when the ReportProgress method is called.
public void ProcessDataAsync()
    // Start the time intensive method
    BackgroundWorker bw = new BackgroundWorker();
    bw.DoWork += BwDoWork;
    bw.RunWorkerCompleted += BwRunWorkerCompleted;

    // Control returns here before TimeintensiveMethod returns
    Console.WriteLine("You can read this while TimeintensiveMethod is still running.");

// Method that will be called after BwDoWork exits
private void BwRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    // we can access possible return values of our Method via the Parameter e
    Console.WriteLine("Count: " + e.Result);

// execution of our time intensive Method
private void BwDoWork(object sender, DoWorkEventArgs e)
    e.Result = TimeintensiveMethod(e.Argument);

private int TimeintensiveMethod(object file)
    Console.WriteLine("Start TimeintensiveMethod.");

    // Do some time intensive calculations...
    using (StreamReader reader = new StreamReader(file.ToString()))
        string s = reader.ReadToEnd();

       for (int i = 0; i < 10000; i++)
    Console.WriteLine("End TimeintensiveMethod.");

    // return something as a "result"
    return new Random().Next(100);