silverlight隔绝存储

cs代码如下：

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;using System.IO.IsolatedStorage;using System.IO;namespace gelicunchu{    public partial class MainPage : UserControl    {        public MainPage()        {            InitializeComponent();        }        private void click1(object sender, RoutedEventArgs e)        {                        using(IsolatedStorageFile store=IsolatedStorageFile.GetUserStoreForApplication()){                Int64 newspace = 20971520;                 Int64 curspace=store.AvailableFreeSpace;                if(curspace<newspace){                    if(!store.IncreaseQuotaTo(newspace)){                        ChildWindow child = new System.Windows.Controls.ChildWindow();                        child.Title = "用户不准许扩展空间";                        child.Content = "请求失败。。。。。。。";                        child.Show();                    }                }                using (StreamWriter sw = new StreamWriter(store.OpenFile("a.txt", FileMode.OpenOrCreate, FileAccess.Write)))                {                    sw.WriteLine(textBox1.Text);                }            }        }        private void click2(object sender, RoutedEventArgs e)        {            using (IsolatedStorageFile store = IsolatedStorageFile.GetUserStoreForApplication())            {                using (StreamReader sr = new StreamReader(store.OpenFile("a.txt", FileMode.OpenOrCreate, FileAccess.Read)))                {                    textBlock1.Text = sr.ReadLine();                }            }        }    }}xaml文件:

<Grid x:Name="LayoutRoot" Background="White">        <Button Content="写入" Height="23" Click="click1"  HorizontalAlignment="Left" Margin="10,10,0,0" Name="button1" VerticalAlignment="Top" Width="75" />        <Button Content="读取" Height="23" Click="click2" HorizontalAlignment="Left" Margin="10,43,0,0" Name="button2" VerticalAlignment="Top" Width="75" />        <TextBox Height="23" HorizontalAlignment="Left" Margin="10,76,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" />        <TextBlock Height="23" HorizontalAlignment="Left" Margin="20,105,0,0" Name="textBlock1" Text="TextBlock" VerticalAlignment="Top" />    </Grid>