public class HttpHelp
    {
        public CookieContainer CookieContainer { get; set; }
 
        public CookieCollection CookieCollection { get; set; }
 
        public HttpHelp()
        {
            this.CookieCollection = new CookieCollection();
            this.CookieContainer = new CookieContainer();
        }
 
        public static string GetHtml(string url, string Referer, Encoding encode)
        {
            return new HttpHelp().GetHtml(url, Referer, encode, false);
        }
 
        public static string PostHtml(string url, string Referer, string data, Encoding encode)
        {
            return new HttpHelp().PostHtml(url, Referer, data, encode, false);
        }
 
        public string GetHtml(string url, string Referer, Encoding encode, bool SaveCookie)
        {
            HttpWebRequest req = WebRequest.Create(url) as HttpWebRequest;
            req.Method = "GET";
            req.CookieContainer = this.CookieContainer;
            req.Proxy = null;
            if (!string.IsNullOrEmpty(Referer))
                req.Referer = Referer;
            using (HttpWebResponse hwr = req.GetResponse() as HttpWebResponse)
            {
                if (SaveCookie)
                {
                    this.CookieCollection = hwr.Cookies;
                    this.CookieContainer.GetCookies(req.RequestUri);
                }
                using (StreamReader SR = new StreamReader(hwr.GetResponseStream(), encode))
                {
                    return SR.ReadToEnd();
                }
            }
        }
 
        public string PostHtml(string url, string Referer, string data, Encoding encode, bool SaveCookie)
        {
            HttpWebRequest req = WebRequest.Create(url) as HttpWebRequest;
            req.CookieContainer = this.CookieContainer;
            req.ContentType = "application/x-www-form-urlencoded";
            req.Method = "POST";
            req.UserAgent = "Mozilla/5.0 (Windows NT 5.1; rv:30.0) Gecko/20100101 Firefox/30.0";
            req.Proxy = null;
            req.ProtocolVersion = HttpVersion.Version10;
            if (!string.IsNullOrEmpty(Referer))
                req.Referer = Referer;
            byte[] mybyte = Encoding.Default.GetBytes(data);
            req.ContentLength = mybyte.Length;
            using (Stream stream = req.GetRequestStream())
            {
                stream.Write(mybyte, 0, mybyte.Length);
            }
            using (HttpWebResponse hwr = req.GetResponse() as HttpWebResponse)
            {
                if (SaveCookie)
                {
                    this.CookieCollection = hwr.Cookies;
                    this.CookieContainer.GetCookies(req.RequestUri);
                }
                using (StreamReader SR = new StreamReader(hwr.GetResponseStream(), encode))
                {
                    return SR.ReadToEnd();
                }
            }
        }
 
        ///
        /// 上传文件
        ///
        ///上传地址
        ///文件路径
        ///原网页file控件name
        ///请求流中的contentType
        ///返回的encoding
        ///post参数字典
        ///
        public static string PostFile(string url, string filepath, string paramName, string contentType, Encoding encode, Dictionary<string, string> dict)
        {
            HttpWebRequest hrq = WebRequest.Create(url) as HttpWebRequest;
            string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
            byte[] boundarybytes = System.Text.Encoding.Default.GetBytes("\r\n--" + boundary + "\r\n");
            hrq.ContentType = "multipart/form-data; boundary=" + boundary;
            hrq.Method = "POST";
 
            using (Stream stream = hrq.GetRequestStream())   //请求流
            {
                //写入post参数
                string formdataTemplete = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
                if (dict != null && dict.Count > 0)
                {
                    foreach (KeyValuePair<string, string> pair in dict)
                    {
                        stream.Write(boundarybytes, 0, boundarybytes.Length);
                        string formitem = string.Format(formdataTemplete, pair.Key, pair.Value);
                        byte[] formitemBytes = Encoding.Default.GetBytes(formitem);
                        stream.Write(formitemBytes, 0, formitemBytes.Length);
                    }
                }
                stream.Write(boundarybytes, 0, boundarybytes.Length);
 
                //写入头信息
                string headerTemplate = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n";
                string header = string.Format(headerTemplate, paramName, Path.GetFileName(filepath), contentType);
                byte[] headerBytes = Encoding.UTF8.GetBytes(header);
                stream.Write(headerBytes, 0, headerBytes.Length);
 
                //写入文件
                byte[] fileBytes = File.ReadAllBytes(filepath);
                stream.Write(fileBytes, 0, fileBytes.Length);
 
                //写入尾部
                byte[] footerBytes = Encoding.Default.GetBytes("\r\n--" + boundary + "--\r\n");
                stream.Write(footerBytes, 0, footerBytes.Length);
 
                using (HttpWebResponse hrp = hrq.GetResponse() as HttpWebResponse)//响应流
                {
                    using (StreamReader SR = new StreamReader(hrp.GetResponseStream(), encode))
                    {
                        return SR.ReadToEnd();
                    }
                }
            }
 
        }
    }