A simple, finite animation

   
  
<Window x:Class="Holding.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="FillingExample" Height="300" Width="300">
  <Canvas>
    <Ellipse Name="myEllipse" Height="100" Fill="Red">
      <Ellipse.Triggers>
        <EventTrigger RoutedEvent="Ellipse.Loaded">
          <BeginStoryboard>
            <Storyboard>
              <DoubleAnimation BeginTime="0:0:2" Duration="0:0:5"
                  Storyboard.TargetProperty="(Ellipse.Width)"
                  From="10" To="300" />
            </Storyboard>
          </BeginStoryboard>
        </EventTrigger>
      </Ellipse.Triggers>
    </Ellipse>
  </Canvas>
</Window>

//File:Window.xaml.cs
using System;
using System.Windows;
using System.Windows.Threading;
using System.Diagnostics;

namespace Holding
{
    public partial class Window1 : Window
    {

        DispatcherTimer t = new DispatcherTimer();
        DateTime start;

        public Window1()
        {
            InitializeComponent();

            t.Tick += new EventHandler(OnTimerTick);
            t.Interval = TimeSpan.FromSeconds(0.5);
            t.Start();
            start = DateTime.Now;
        }

        void OnTimerTick(object sender, EventArgs e)
        {
            TimeSpan elapsedTime = DateTime.Now - start;
            Debug.WriteLine(elapsedTime.ToString() + ": " + myEllipse.Width);
        }
    }
}