silverlight - How to create a rounded corner border

how to create rounded corner border in silverlight
MainPage.xaml

<UserControl 
    x:Class="SilverlightApps.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" 
    xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"
    >

    <Grid x:Name="LayoutRoot" Background="White">
        <TextBlock 
            Height="82" 
            HorizontalAlignment="Left" 
            Margin="20,12,0,0" 
            Name="textBlock1" 
            Text="Silverlight - how to create rounded corner border"
            VerticalAlignment="Top"
            TextWrapping="Wrap"
            FontSize="20"
            FontStyle="Italic"
            Foreground="MidnightBlue"
            Width="625"
            />

        <Border 
            Name="border1"
            BorderBrush="Black" 
            BorderThickness="1" 
            HorizontalAlignment="Left" 
            Height="48"
            Margin="35,85,0,0" 
            VerticalAlignment="Top"
            Width="204"
            CornerRadius="3"
            />

        <Border 
            Name="border2"
            BorderBrush="Green" 
            BorderThickness="2" 
            HorizontalAlignment="Left" 
            Height="132"
            Margin="35,156,0,0" 
            VerticalAlignment="Top"
            Width="204"
            CornerRadius="10"
            />

        <Border 
            Name="border3"
            BorderBrush="Red" 
            BorderThickness="3" 
            HorizontalAlignment="Left" 
            Height="178"
            Margin="285,94,0,0" 
            VerticalAlignment="Top"
            Width="204"
            CornerRadius="25"
            />
    </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 SilverlightApps
{
    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
        }
    }
}
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