Question

I want to show a new form with a progress bar marquee. This form should be on an other thread, since the action that is called is too big and the UI doesn’t update the progress bar if it’s on the same thread.

I call a new thread, create my form, but as soon as it appears, the form close…

Here is my code from my main :

    frmProgress f = new frmProgress();
    Thread t = new Thread(new ThreadStart(delegate() { f.Show(); }));
    t.Start();
    documentManager.Compile(); //This is my big action
    t.Abort();

Here is the code of form :

    public frmProgress()
    {
        InitializeComponent();
    }

I would like to know what I did wrong.

Thanks!

Answer 1

You have several problems:

1. You’re showing a form in a non-UI thread. This will only cause problems; it needs to be in the UI thread.
2. You’re performing a long running task in the UI thread; this is blocking UI updates.

You need to be showing the forum in the UI thread, and running the long running task in a background thread.

A great tool for the job here is to use a BackgroundWorker. It will do much of the work for you to ensure the proper code is running in the UI/non-UI threads as it should be. Create a new BackgroundWorker and put the long running task in the DoWork event. Make any simple UI updates that you need to (showing the form) before you start the BGW, and do any cleanup in the Completed event (which will run in the UI). The MSDN page on BackgroundWorker has some nice examples.

Another advantage of using a BackgroundWorker is that you can easily report progress (if you have a good way of knowing your % complete) rather than just having a marquee bar. Just add a handler to the ProgressReported event handler to update the progress bar, and call the ReportProgress method periodically when doing work. See the linked examples for exact code snippets.