Windows Forms ProgressBar: Easiest way to start/stop marquee?

Question

Use a progress bar with the style set to Marquee. This represents an indeterminate progress bar.

myProgressBar.Style = ProgressBarStyle.Marquee;

You can also use the MarqueeAnimationSpeed property to set how long it will take the little block of color to animate across your progress bar.

To start/stop the animation, you should do this:

To start:

progressBar1.Style = ProgressBarStyle.Marquee;
progressBar1.MarqueeAnimationSpeed = 30;

To stop:

progressBar1.Style = ProgressBarStyle.Continuous;
progressBar1.MarqueeAnimationSpeed = 0;

It's not how they work. You "start" a marquee style progress bar by making it visible, you stop it by hiding it. You could change the Style property.

This code is a part of a login form where the users wait for the authentication server to respond.

using System;
using System.ComponentModel;
using System.Threading;
using System.Windows.Forms;

namespace LoginWithProgressBar
{
    public partial class TheForm : Form
    {
        // BackgroundWorker object deals with the long running task
        private readonly BackgroundWorker _bw = new BackgroundWorker();

        public TheForm()
        {
            InitializeComponent();

            // set MarqueeAnimationSpeed
            progressBar.MarqueeAnimationSpeed = 30;

            // set Visible false before you start long running task
            progressBar.Visible = false;

            _bw.DoWork += Login;
            _bw.RunWorkerCompleted += BwRunWorkerCompleted;
        }

        private void BwRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            // hide the progress bar when the long running process finishes
            progressBar.Hide();
        }

        private static void Login(object sender, DoWorkEventArgs doWorkEventArgs)
        {
            // emulate long (3 seconds) running task
            Thread.Sleep(3000);
        }

        private void ButtonLoginClick(object sender, EventArgs e)
        {
            // show the progress bar when the associated event fires (here, a button click)
            progressBar.Show();

            // start the long running task async
            _bw.RunWorkerAsync();
        }
    }
}    

There's a nice article with code on this topic on MSDN. I'm assuming that setting the Style property to ProgressBarStyle.Marquee is not appropriate (or is that what you are trying to control?? -- I don't think it is possible to stop/start this animation although you can control the speed as @Paul indicates).

Many good answers here already, although you also need to keep in mind that if you are doing long-running processing on the UI thread (generally a bad idea), then you won't see the marquee moving either.