C#

//Form Class
void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
    // Get the BackgroundWorker that raised this event.
    BackgroundWorker worker = sender as BackgroundWorker;

    e.Result = MyTimeConsumingTask(e.Argument, worker, e);

}

void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    // First, handle the case where an exception was thrown.
    if (e.Error != null)
    {
        MessageBox.Show(e.Error.Message);
    }
    else if ((bool)e.Result)
    {
        //MyTimeConsumingTask successfully executed
    }
    else
    {
        //MyTimeConsumingTask failed
    }
}
//Form Class end


//Another Class
internal bool MyTimeConsumingTask(object arg, BackgroundWorker worker, DoWorkEventArgs e)
{
    //Actual task is performed here, for simplicity sleep has been used.
    Thread.Sleep(10000);
    return true;
}
//Another Class end