backgroundworker not firing RunWorkerCompleted event

Question

i have a web application with a search form. The form is being used to search through my own database, but also at other databases through their API service. To provide a fast response, i have decided to split the work in main thread and the backgroundworker service.

Here is my method which runs the search task.

// search through other API
BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
worker.WorkerSupportsCancellation = true;
worker.WorkerReportsProgress = true;
worker.RunWorkerAsync(form);

// search in my api
...

// wait for API results
while (worker.IsBusy) {
    for (sbyte i = 0; i < sbyte.MaxValue; i++) ;
}
// handle data and show to user

And the methods are

private void worker_DoWork(object sender, DoWorkEventArgs e) {
    Forms f = e.Argument as Forms;
    if (f != null) {
        List<ApiResponse> result = GetDataFromOtherApi(f);
        e.Result = result;
    }
    else e.Result = null;
}

The GetDataFromOtherApi() method works fine in the single thread test. It also works when running the backgroundworker thread. I have set a breakpoint at the end and e.Result has values which i was looking for.

private void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
    List<ApiResponse> reply = e.Result as List<ApiResponse>;

    if (reply == null) ar = null;
    else if (reply.Any()) ar = reply;
    else ar = null;
}

the ar is a variable that the main thread can access to after the while loop has done with running. But, when placing a breakpoint at the start, it never stops there, the loop itself is continuous to the infinity ... It means that the event is never being fired.

Am i missing something ?

Answer 1

The BackgroundWorker progress & completed events are synchronised to run on the UI thread. I'd guess as you're blocking that thread, they'll never get fired.