Create DoubleAnimation and Animate a Button with Button.BeginAnimation and Button.WidthProperty


   
  
<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);
    }
}