silverlight - How to use RadioButton click event

silverlight - how to use RadioButton Click event
MainPage.xaml

<UserControl x:Class="SilverlightApplication2.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="600"
    d:DesignWidth="800">

    <Grid x:Name="LayoutRoot" Background="White">
        <Rectangle
            Name="Rectangle1"
            Fill="AliceBlue" 
            HorizontalAlignment="Left" 
            Height="82" 
            Margin="20,12,0,0" 
            Stroke="Black" 
            VerticalAlignment="Top" 
            Width="600"
            StrokeThickness="0"
            />
        <TextBlock 
            Height="82" 
            HorizontalAlignment="Left" 
            Margin="20,9,0,0" 
            Name="TextBlock1" 
            Text="silverlight - how to use RadioButton Click event"
            VerticalAlignment="Top"
            TextWrapping="Wrap"
            FontSize="20"
            FontStyle="Italic"
            Foreground="MidnightBlue"
            Width="600"
            Padding="25,10,10,0"
            />

        <RadioButton 
            Content="Gray" 
            GroupName="ColorsName" 
            HorizontalAlignment="Left" 
            Margin="50,112,0,0" 
            VerticalAlignment="Top"
            Click="RadioButton_Click"
            x:Name="GrayRadio"
            />
        <RadioButton 
            Content="Yellow" 
            GroupName="ColorsName" 
            HorizontalAlignment="Left" 
            Margin="50,152,0,0" 
            VerticalAlignment="Top"
            Click="RadioButton_Click"
            x:Name="YellowRadio"
            />
        <RadioButton 
            Content="Orange" 
            GroupName="ColorsName" 
            HorizontalAlignment="Left" 
            Margin="50,187,0,0" 
            VerticalAlignment="Top"
            Click="RadioButton_Click"
            x:Name="OrangeRadio"
            />
    </Grid>
</UserControl>
MainPage.xaml.cs

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 SilverlightApplication2
{
    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
        }

        private void RadioButton_Click(object sender, RoutedEventArgs e)
        {
            if (GrayRadio.IsChecked == true)
            {
                Rectangle1.Fill = new SolidColorBrush(Colors.Gray);
            }

            if (YellowRadio.IsChecked == true)
            {
                Rectangle1.Fill = new SolidColorBrush(Colors.Yellow);
            }

            if (OrangeRadio.IsChecked == true)
            {
                Rectangle1.Fill = new SolidColorBrush(Colors.Orange);
            }
        }
    }
}