silverlight - How to preserve white space in a TextBlock

how to preserve white space in TextBlock 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">
        <Rectangle
            Name="Rectangle1"
            Fill="AliceBlue" 
            HorizontalAlignment="Left" 
            Height="82" 
            Margin="20,12,0,0" 
            Stroke="Black" 
            VerticalAlignment="Top" 
            Width="600"
            StrokeThickness="0"
            />

        <TextBlock 
            Name="TextBlock1" 
            Height="82" 
            HorizontalAlignment="Left" 
            Margin="20,9,0,0" 
            Text="how to preserve white space in TextBlock in silverlight"
            VerticalAlignment="Top"
            TextWrapping="Wrap"
            FontSize="20"
            FontStyle="Italic"
            Foreground="MidnightBlue"
            Width="600"
            Padding="25,10,10,0"
            />

        <TextBlock
            Name="TextBlock2"
            Height="250"
            FontFamily="Courier New"
            FontSize="15"
            Foreground="Red"
            Padding="25,0,0,0"
            >
            
            This is a line without preserve space.
            And this is line 2.
        </TextBlock>

        <TextBlock
            Name="TextBlock3"
            Height="250"
            FontFamily="Courier New"
            FontSize="15"
            Foreground="Green"
            xml:space="preserve" Margin="0,217,0,133"
            >
            This is a line with preserve space.
            This is line 2 with preserve space.
        </TextBlock>

        <TextBlock
            Name="TextBlock4"
            Height="250"
            FontFamily="Courier New"
            FontSize="15"
            Foreground="Blue"
            xml:space="preserve" Margin="0,317,0,33"
            >
            This is a line with preserve space.
                This is line 2 with preserve space and single tab.
                    This is line 2 with preserve space and two tab.
        </TextBlock>
    </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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