C# 获取网络路径文件大小信息的方法

做一个获取网络文件的大小信息的小软件，由于我的电脑上网使用的是HTTP代理，所以FTp部分是不能测试代码的可行性，所以先把代码贴出来：

//输入返回文件信息，包括文件名，格式，大小，以及其他信息

private string GetInfo(string URL)
{
    string Results = "";
    string filetype = URL.Substring(URL.LastIndexOf(".") + 1,
    (URL.Length - URL.LastIndexOf(".") - 1));
    Results = "类型：" + filetype.ToUpper();
    string filename = URL.Substring(URL.LastIndexOf("/") + 1,
    (URL.Length - URL.LastIndexOf("/") - 1));
    Results += "|名称：" + filename;
    long ContentL = 0;
    if (URL.ToLower().StartsWith("http://"))
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);

        request.MaximumAutomaticRedirections = 4;
        request.MaximumResponseHeadersLength = 4;
        request.Credentials = CredentialCache.DefaultCredentials;
        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        ContentL = response.ContentLength;
        response.Close();

        Results += "|大小：" + GetSize(ContentL) + "|额外信息：" + response.Server;

    }
    else if (URL.ToLower().StartsWith("ftp://"))
    {

        FtpWebRequest request = (FtpWebRequest)WebRequest.Create(URL);
        request.Method = WebRequestMethods.Ftp.GetFileSize;
        request.UseBinary = true;
        FtpWebResponse response = null;
        response = (FtpWebResponse)request.GetResponse();
        Stream Fs = response.GetResponseStream();
        ContentL = response.ContentLength;
        Fs.Close();
        response.Close();

        Results += "|大小：" + GetSize(ContentL) + "|额外信息：" + response.WelcomeMessage;
    }
    else
    {
        Results += "|大小：无法检测";
    }

    return Results;
}
//大小转化
private string GetSize(long L)
{
    float result;
    string re = "";
    if (L >= 1073741824)
    {
        result = L / 1073741824.00F;
        re = "GB";
    }
    else if (L >= 1048576)
    {
        result = L / 1048576.00F;
        re = "MB";
    }
    else
    {
        result = L / 1024.00F;
        re = "KB";
    }
    string File_Size = result.ToString("0.00");
    return (File_Size + re);
}

比如像这样的路径是很容易获取信息的：

http://download.hunantv.com/tv/imgotv_1.0.5.5938.exe

但是对于FTP测试的我没有条件测试。