Commands in MVVM

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Threading;

namespace Apex.Controls
{
    /// <summary>
    /// Provides a circular progress bar
    /// </summary>
  public partial class CircularProgressBar : UserControl
  {
    public CircularProgressBar()
    {
      InitializeComponent();

      animationTimer = new DispatcherTimer(
          DispatcherPriority.ContextIdle, Dispatcher);
      animationTimer.Interval = new TimeSpan(0, 0, 0, 0, 75);
    }

    private readonly DispatcherTimer animationTimer;
      
    private void Start()
    {
      animationTimer.Tick += HandleAnimationTick;
      animationTimer.Start();
    }

    private void Stop()
    {
      animationTimer.Stop();
      animationTimer.Tick -= HandleAnimationTick;
    }

    private void HandleAnimationTick(object sender, EventArgs e)
    {
      SpinnerRotate.Angle = (SpinnerRotate.Angle + 36) % 360;
    }

    private void HandleLoaded(object sender, RoutedEventArgs e)
    {
      const double offset = Math.PI;
      const double step = Math.PI * 2 / 10.0;

      SetPosition(C0, offset, 0.0, step);
      SetPosition(C1, offset, 1.0, step);
      SetPosition(C2, offset, 2.0, step);
      SetPosition(C3, offset, 3.0, step);
      SetPosition(C4, offset, 4.0, step);
      SetPosition(C5, offset, 5.0, step);
      SetPosition(C6, offset, 6.0, step);
      SetPosition(C7, offset, 7.0, step);
      SetPosition(C8, offset, 8.0, step);
    }

    private void SetPosition(Ellipse ellipse, double offset,
        double posOffSet, double step)
    {
      ellipse.SetValue(Canvas.LeftProperty, 50.0
          + Math.Sin(offset + posOffSet * step) * 50.0);

      ellipse.SetValue(Canvas.TopProperty, 50
          + Math.Cos(offset + posOffSet * step) * 50.0);
    }

    private void HandleUnloaded(object sender, RoutedEventArgs e)
    {
      Stop();
    }

    private void HandleVisibleChanged(object sender,
        DependencyPropertyChangedEventArgs e)
    {
      bool isVisible = (bool)e.NewValue;

      if (isVisible)
        Start();
      else
        Stop();
    }

    private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
    }

    public static DependencyProperty ProgressTextProperty = DependencyProperty.Register("ProgressText", typeof(string), typeof(CircularProgressBar));

    public string ProgressText
    {
      get { return (string)GetValue(ProgressTextProperty); }
      set { SetValue(ProgressTextProperty, value); }
    }
  }
}