Hi,

You have to use a thread to perform the operation and in the meantime in the
UI thread the progress bar is running.
Take a look at Control.Invoke as the way to communication between the worker
thread and the UI

Hi Steve

An event should work fine here, but you also need to start your processing in a BackgroundWorker or another thread or the main thread won't get time to process the event.  And since the event will get caught in a thread other than the main thread, you need to use Invoke as well.  The sample below might give you some ideas.  If you don't mind having the class call the form directly (which isn't really good OO practice, you can skip throwing the event and call the form directly)

    public class MyForm : Form
    {

        <...>

        delegate void ProgressBarDelegate(int value);
        BackgroundWorker worker = new BackgroundWorker();
        MyClass myClass = new MyClass();

        private void Method()
        {
            myClass.MyEvent += new MyClass.MyEventHandler(myClass_MyEvent);
            worker.DoWork += new DoWorkEventHandler(worker_DoWork);
            worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
            worker.RunWorkerAsync();
        }

        void myClass_MyEvent(int value)
        {
            if (progressBar1.InvokeRequired)
                progressBar1.Invoke(new ProgressBarDelegate(myClass_MyEvent), new object[] { value });
            else
                progressBar1.Value = value / 2;
        }

        void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            myClass.Method();
        }

        void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            MessageBox.Show("Done");
        }
    }

    public class MyClass
    {
        public event MyEventHandler MyEvent;
        public delegate void MyEventHandler(int value);

        public void Method()
        {
            for (int i = 0; i < 200; i++)
            {
                System.Threading.Thread.Sleep(200);
                MyEvent(i);
            }
        }
    }