< Canvas.RenderTransform > 
< ScaleTransform x:Name="CanvasScale" ScaleX="1" ScaleY="1" > < /ScaleTransform > 
< /Canvas.RenderTransform > 

< 
UserControl xmlns:inputToolkit="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Input.Toolkit" x:Class="SilverlightApplication1.Page"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
Width="400" Height="300" > 
< Grid x:Name="LayoutRoot" Background="White" > 
< Canvas Height="150" Width="400" Background="Bisque" VerticalAlignment="Center"  > 
< Canvas.RenderTransform > 
< ScaleTransform x:Name="CanvasScale" ScaleX="1" ScaleY="1" > < /ScaleTransform > 
< /Canvas.RenderTransform > 
< Button x:Name="myButton" Canvas.Top="50" 
Canvas.Left="75" Content="Click Me" 
Height="37" Width="118" Click="myButton_Click" 
ToolTipService.ToolTip ="Click to change above text"/ > 
< Button x:Name="myButton1" Canvas.Top="50" 
Canvas.Left="195" Content="Click Me" 
Height="37" Width="118"/ > 
< /Canvas > 
< /Grid > 
< /
UserControl > 

App.Current.Host.Content.Resized += new EventHandler(Content_Resized);

void
Content_Resized(object sender, EventArgs e)
{ 
double height = App.Current.Host.Content.ActualHeight; 
double width = App.Current.Host.Content.ActualWidth;
CanvasScale.ScaleX = width / _startingWidth; 
CanvasScale.ScaleY = height / _startingHeight; 
}

using
System;
using
System.Collections.Generic;
using
System.Linq;
using
System.Net;
using
System.Windows;
using
System.Windows.Controls;
using
System.Windows.Documents;
using
System.Windows.Input;
using
System.Windows.Media;
using
System.Windows.Media.Animation;
using
System.Windows.Shapes;
namespace
SilverlightApplication1
{
public partial class Page : UserControl
{
private int _startingWidth = 800; 
private int _startingHeight = 600;
public Page()
{
InitializeComponent(); 
App.Current.Host.Content.Resized += new EventHandler(Content_Resized);
}
private void myButton_Click(object sender, RoutedEventArgs e)
{
}
void Content_Resized(object sender, EventArgs e)
{ 
double height = App.Current.Host.Content.ActualHeight; 
double width = App.Current.Host.Content.ActualWidth;
CanvasScale.ScaleX = width / _startingWidth; 
CanvasScale.ScaleY = height / _startingHeight; 
}
}
}