Check out the BackgroundWorker class:

http://msdn2.microsoft.com/en-us/library/system.componentmodel.backgroundworker.aspx

  Regards,
  Gilles.

Hi Chris

I apologize if this answer appears twice, but I got an error trying to post
the previous answer, so here goes.

When you do heavy processing inside the GUI thread (main thread in a windows
application) you won't have any processing time to perform GUI stuff.  This
will cause a gray and/or non responsive interface.

You should move any heavy processing to a separate thread.  The easiest way
to do this is by using a BackgroundWorker object like Gilles points out.

Below is an example of how this can be done using a background worker that
reports progress as well as supports aborting.  Add a progressbar control as
well as two buttons with their Click event attached to button1_Click and
button2_Click

private BackgroundWorker worker;
public Form2()
{
   InitializeComponent();

   worker = new BackgroundWorker();

   // Needed to fire the progresschanged event
   worker.WorkerReportsProgress = true;

   // Needed to be able to stop the processing
   worker.WorkerSupportsCancellation = true;

   // Any heavy processing should spawn from this event
   worker.DoWork += new DoWorkEventHandler(worker_DoWork);

   // This event fires when you want it to
   worker.ProgressChanged += new
ProgressChangedEventHandler(worker_ProgressChanged);

   // This event fires when the worker is done processing
   worker.RunWorkerCompleted += new
RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
}

private void button1_Click_1(object sender, EventArgs e)
{
   // Resett progressbar
   progressBar1.Value = 0;

   // Notify the worker object to start working
   worker.RunWorkerAsync(@"C:\temp");
   // You can put anything as an argument to this method
}

private void button2_Click(object sender, EventArgs e)
{
   // Stop working
   if (worker.IsBusy)
       worker.CancelAsync();
}

void worker_DoWork(object sender, DoWorkEventArgs e)
{
   DateTime start = DateTime.Now;

   // This method is called when you use RunWorkerAsync

   string path = e.Argument.ToString();
   // e.Argument can be anything, including a complex object

   for (int i = 0; i < 100; i++)
   {
       // Did someone cancel the work?
       if (worker.CancellationPending)
       {
           // if so, then simply return
           return;
       }

       // Simulate processing of a single file
       // which in this case would take 1 seconds
       // to process.
       System.Threading.Thread.Sleep(1000);

       // Report the number of files processed
       worker.ReportProgress(i + 1);
       // The parameter says intPercentage,
       // but it can be any number you like
   }

   // the Result property can be used to provide information
   e.Result = "100 files processed in " + (DateTime.Now -
start).TotalSeconds + " minutes";
}

void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
   // If the worker calls ReportProgress this method will be called.
   progressBar1.Value = e.ProgressPercentage;
}

void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
   // This method will be called when the worker is done processing or
cancelled

   if (e.Result == null)
       MessageBox.Show("Processing aborted");
   else
       MessageBox.Show(e.Result.ToString());
}