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。