Question

I have tried to navigate through a couple of web pages using an backgroundworker & webbrowser. Im using this function which it doesnt work. Im not sure what is going wrong here.

I see only the MessageBox.Show(arr[0]); nothing else. the webbrowser doesnt change too

private void bw_DoWork(object sender, DoWorkEventArgs e)
{
    string[] arr = { "http://stackoverflow.com/", "http://www.codeproject.com/", "http://www.codeplex.com/" };
    for (int i = 0; i < 3; i++)
    {
        MessageBox.Show(arr[i]);
        bB_checker.Invoke((EventHandler)delegate { bB_checker.Navigate(arr[i]); });
        while (bB_checker.ReadyState != WebBrowserReadyState.Complete)
        {
            //  System.Threading.Thread.Sleep(100);
            Application.DoEvents();
        }
    }
}

Answer 1

Never implement BGW without checking the e.Error property in the RunWorkerCompleted event handler:

    private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
        if (e.Error != null) MessageBox.Show(e.Error.ToString());
    }

The somewhat mysterious invalid cast exception is caused by using the ReadyState property on a worker thread. WebBrowser is not threadsafe. Check this answer for a way to create a WB on a worker thread.

That’s not however a good way if you need to keep the browser visible to the user. You’ll have to give up on using threading in that case. Not a real problem, just count up the array index in the DocumentCompleted event handler. Albeit that it makes little sense to flash these web pages.