C# 在wp7的后台从web下载文件

我正在用c语言为wp7编写一个应用程序：2页[主页，第二页]。
应用程序在mainpage中启动，然后用户可以在secondpage中导航到secondpage（使用NavigationService.navigate）

在secondpage中，WebClient在isolatedStorage中下载一个文件

我的问题是，当用户使用back键返回主页时，下载会冻结

有没有一种方法可以在后台实现这一点，这样用户就可以导航并自由地抛出页面

下面是secondpage类的代码（单击事件中还有一个带有webClient.OpenReadAsync（uri）的按钮）

---

查看-听起来这正是您完成需求所需要的。

您查看了BackgroundWorker类了吗

public partial class SecondPage : PhoneApplicationPage
{
    WebClient webClient = new WebClient();
    IsolatedStorageFile Storage = IsolatedStorageFile.GetUserStoreForApplication();

    public SecondPage()
    {
        InitializeComponent();
        webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
        webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(webClient_OpenReadCompleted);
    }
    void webClient_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
    {
        try
        {
            if (e.Result != null)
            {
                string fileName = "download.txt";
                IsolatedStorageFileStream f = new IsolatedStorageFileStream(fileName, System.IO.FileMode.Create, Storage);
                long fileNameLength = (long)e.Result.Length;
                byte[] byteImage = new byte[fileNameLength];
                e.Result.Read(byteImage, 0, byteImage.Length);
                f.Write(byteImage, 0, byteImage.Length);
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

    void webClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
    {
        try
        {
            if (ProgressDownload.Value <= ProgressDownload.Maximum)
            {
                ProgressDownload.Value = (double)e.ProgressPercentage;
            }

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }
}

    private void bw_DoWork(object sender, DoWorkEventArgs e)
    {
        BackgroundWorker worker = sender as BackgroundWorker;

        WebClient webClient = new WebClient();
        webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
        webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(webClient_OpenReadCompleted);


        webClient.OpenReadAsync(new Uri("http://foo.com/asd.txt"));

    }