display Hourglass when application is busy

We did a disposable class that changes the cursor for us when the app is going to take long, it looks like this:

public class WaitCursor : IDisposable
{
    private Cursor _previousCursor;

    public WaitCursor()
    {
        _previousCursor = Mouse.OverrideCursor;

        Mouse.OverrideCursor = Cursors.Wait;
    }

    #region IDisposable Members

    public void Dispose()
    {
        Mouse.OverrideCursor = _previousCursor;
    }

    #endregion
}

And we use it like this:

using(new WaitCursor())
{
    // very long task
}

Might not be the greatest design, but it does the trick =)

I used the answers here to build something that worked better for me. The problem is that when the using block in Carlo's answer finishes, the UI might actually still be busy databinding. There might be lazy-loaded data or events firing as a result of what was done in the block. In my case it sometimes took several seconds from the waitcursor disappeared until the UI was actually ready. I solved it by creating a helper method that sets the waitcursor and also takes care of setting up a timer that will automatically set the cursor back when the UI is ready. I can't be sure that this design will work in all cases, but it worked for me:

    /// <summary>
    ///   Contains helper methods for UI, so far just one for showing a waitcursor
    /// </summary>
    public static class UiServices
    {

    /// <summary>
    ///   A value indicating whether the UI is currently busy
    /// </summary>
    private static bool IsBusy;

    /// <summary>
    /// Sets the busystate as busy.
    /// </summary>
    public static void SetBusyState()
    {
        SetBusyState(true);
    }

    /// <summary>
    /// Sets the busystate to busy or not busy.
    /// </summary>
    /// <param name="busy">if set to <c>true</c> the application is now busy.</param>
        private static void SetBusyState(bool busy)
        {
            if (busy != IsBusy)
            {
                IsBusy = busy;
                Mouse.OverrideCursor = busy ? Cursors.Wait : null;

                if (IsBusy)
                {
                    new DispatcherTimer(TimeSpan.FromSeconds(0), DispatcherPriority.ApplicationIdle, dispatcherTimer_Tick, Application.Current.Dispatcher);
                }
            }
        }

        /// <summary>
        /// Handles the Tick event of the dispatcherTimer control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param>
        private static void dispatcherTimer_Tick(object sender, EventArgs e)
        {
                var dispatcherTimer = sender as DispatcherTimer;
                if (dispatcherTimer != null)
                {
                    SetBusyState(false);
                    dispatcherTimer.Stop();
                }
        }
    }