网络文件下载

下载验证码等网络资源

using System.IO;
using System.IO.Compression;
using System.Net;

namespace ConsoleApplication2
{
    public static class HttpFileDownloader
    {
        public static byte[] DownLoad(string url)
        {
            byte[] buffer = null;
            HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(url);
            req.UserAgent = "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)";
            req.Headers.Add("Accept-Encoding", "gzip, deflate");
            req.KeepAlive = true;

            using (HttpWebResponse response = (HttpWebResponse)req.GetResponse())
            {
                Stream reader;
                if (response.ContentEncoding.ToLower().Contains("gzip"))
                {
                    reader = new System.IO.Compression.GZipStream(response.GetResponseStream(), CompressionMode.Decompress);
                }
                else
                {
                    reader = response.GetResponseStream();
                }
                if (reader.CanRead)
                {
                    MemoryStream ms = new MemoryStream();
                    reader.CopyTo(ms);
                    buffer = ms.GetBuffer();
                }
                reader = null;
            }

            req = null;
            return buffer;
        }
    }
}

 保存到本地

        static void Main(string[] args)
        {
            string url = "https://kyfw.12306.cn/otn/passcodeNew/getPassCodeNew?module=login&rand=sjrand" + "&rnd=" + DateTime.Now.Millisecond;
            byte[] buffer = HttpFileDownloader.DownLoad(url);
            if (buffer!=null)
            {
                System.IO.File.WriteAllBytes(@"d:img.png", buffer);
            }
        }