How to wait correctly until BackgroundWorker completes?

Question

Observe the following piece of code:

var handler = GetTheRightHandler();
var bw = new BackgroundWorker();
bw.RunWorkerCompleted += OnAsyncOperationCompleted;         


        

Answer 1

I used Tasks with a BackgroundWorker

You can create any number of tasks and add them to a list of tasks. The worker will start when a task is added, restart if a task is added while the worker IsBusy, and stop once there are no more tasks.

This will allow you to update the GUI asynchronously as much as you need to without freezing it.

This works as is for me.

    // 'tasks' is simply List that includes events for adding objects
    private ObservableCollection tasks = new ObservableCollection();
    // this will asynchronously iterate through the list of tasks 
    private BackgroundWorker task_worker = new BackgroundWorker();

    public Form1()
    {
        InitializeComponent();
        // set up the event handlers
        tasks.CollectionChanged += tasks_CollectionChanged;
        task_worker.DoWork += task_worker_DoWork;
        task_worker.RunWorkerCompleted += task_worker_RunWorkerCompleted;
        task_worker.WorkerSupportsCancellation = true;

    }

    // ----------- worker events
    void task_worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        if (tasks.Count != 0)
        {
            task_worker.RunWorkerAsync();
        }
    }

    void task_worker_DoWork(object sender, DoWorkEventArgs e)
    {
        try
        {

            foreach (Task t in tasks)
            {
                t.RunSynchronously();
                tasks.Remove(t);
            }
        }
        catch
        {
            task_worker.CancelAsync();
        }
    }


    // ------------- task event
    // runs when a task is added to the list
    void tasks_CollectionChanged(object sender,
        System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        if (!task_worker.IsBusy)
        {
            task_worker.RunWorkerAsync();
        }
    }

Now all you need is to create a new Task and add it to the List<>. It will be run by the worker in the order it was placed into the List<>

Task t = new Task(() => {

        // do something here
    });

    tasks.Add(t);