问从IIS检索名为C# .Net的特殊字符文件

EN

    private WebClient webClient;
    private BackgroundWorker bgWorker;
    private string tempFile;
    private string md5;
    internal string TempFilePath
    {
        get { return this.tempFile; }
    }
    internal UpdateInfoDownloadForm(Uri location, string md5, Icon programIcon)
    {
        InitializeComponent();
        if (programIcon != null)
        {
            this.Icon = programIcon;
        }
        tempFile = Path.GetTempFileName();
        this.md5 = md5;
        webClient = new WebClient();
        webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
        webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(webClient_DownloadFileCompleted);

        bgWorker = new BackgroundWorker();
        bgWorker.DoWork += new DoWorkEventHandler(bgWorker_DoWork);
        bgWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(BgWorker_RunWorkerCompleted);

        try
        {
            string strend = location.ToString().Substring(location.ToString().LastIndexOf('/')+1);

            string strstart = location.ToString().Substring(0,location.ToString().LastIndexOf('/')+1);

            strend = System.Web.HttpUtility.UrlEncode(strend);
            Uri locn = new Uri(strstart+strend);
            webClient.DownloadFileAsync(locn, this.tempFile); **//It fails here**
        }
        catch(Exception ex)
        { this.DialogResult = DialogResult.No; this.Close(); }
    }