<Window x:Class="Window1" Title="Animation" Width="300" Height="300" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"> <Canvas> <Button x:Name="b">OK</Button> </Canvas> </Window> //File:Window.xaml.cs using System.Windows; using System.Windows.Controls; using System.Windows.Media.Animation; public partial class Window1 : Window { public Window1() { InitializeComponent(); DoubleAnimation a = new DoubleAnimation(); a.From = 50; a.To = 100; b.BeginAnimation(Button.WidthProperty, a); } }