Question

Saw this in some code but didn’t make sense to me, So I was wondering if even it is a correct way of utilizing backgreound worker?

it is used like this on Form_Load event:

    BackgroundWorker asyncWorker = new BackgroundWorker();
    asyncWorker.DoWork += new DoWorkEventHandler(AsynchDoWork);
    asyncWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(AsynchCompleted);
    asyncWorker.RunWorkerAsync();

   // a for each loop that can take some time to populate a combobx on the form

Also, is there a better alternative on achieving the same goal? other than backgroundworker?

Answer 1

I would use the Task Parralell Library for this. A good into tutorial is Task Parallel Library: 1 of n. To update a combo box following the result of some background task you could do something like this

// Get UI scheduler. Use this to update ui thread in continuation.
TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();

// You can use TPL like this...
List<object> objList = new List<object>();
Task<object[]> task = Task.Factory.StartNew<object[]>(() =>
    {
        // Pull all your data into some object.
        object[] objArr = new object[] { "Some", "Stuff", "..." };
        return objArr;
    }, TaskCreationOptions.PreferFairness);

// Continuation firs after the antecedent task is completed.
task.ContinueWith(ant =>
    {
        // Get returned data set.
        object[] resultSet = (task.Result as object[]);

        // Check task status.
        switch (task.Status)
        {
            // Handle any exceptions to prevent UnobservedTaskException.             
            case TaskStatus.RanToCompletion:
                if (task.Result != null)
                {
                    // Update UI comboBox.
                }
                break;
            default:
                break;
        }
    }, CancellationToken.None, TaskContinuationOptions.None, uiScheduler);

Here the uiScheduler lets you update the ui thread from within the continuation delegate which fires when the antecedent task completes (either successfully or otherwise).

The continuation also acts as an exception handler in this case to catch any AggregateExceptions they may be thrown from the background thread.

I hope this helps.