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前言：

winform程序下载功能，想要在下载前获取到文件的大小等信息并展示到界面上，通过查找发现网上有类似的JAVA代码，于是效仿之~

JAVA代码：

/**
* 获取网络文件大小 
*/
    private static long getFileLength(String downloadUrl) throws IOException{
		  if(downloadUrl == null || "".equals(downloadUrl)){
			  return 0L ; 
		  }
	      URL url = new URL(downloadUrl);
	      HttpURLConnection conn = null;
	      try {
	          conn = (HttpURLConnection) url.openConnection();
	          conn.setRequestMethod("HEAD");
	          conn.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows 7; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/47.0.2526.73 Safari/537.36 YNoteCef/5.8.0.1 (Windows)");
	          return (long) conn.getContentLength();
	      } catch (IOException e) {
	          return 0L;
	      } finally {
	          conn.disconnect();
	    }
     }

C#代码：

public static string GetInfo(string URL)

        {
            string Results = "";

            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 +=  GetSize(ContentL);


            }

            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 += GetSize(ContentL);

            }

            else

            {

                Results += "无法检测";

            }



            return Results;

        }

        //大小转化  

        public static 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);

        }