private BackgroundWorker worker;
worker = new BackgroundWorker();
worker.WorkerReportsProgress = true;
worker.WorkerSupportsCancellation = true;
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
worker.ProgressChanged += new ProgressChangedEventHandler(worker_ProgressChanged);
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);

        public void Start()
        {
            string[] config = { "task1", "task2", "task3" };
            foreach (string task in config)                            //<--- 1
            {
                BackgroundWorker worker = new BackgroundWorker();
                worker.DoWork += DoWork;
                worker.RunWorkerAsync(task);                           //<--- 2,3
            }
        }

        void DoWork(object sender, DoWorkEventArgs e)
        {
            string taskDescription = e.Argument as string;             //<--- 3
            while (true)
            {
                Console.WriteLine(taskDescription);
                System.Threading.Thread.Sleep(500);
            }
        }