HttpWebRequest

     public static class HttpHelper
    {
        private static readonly string DefaultUserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";

        private static Encoding requestEncoding = Encoding.UTF8;

        public static bool HttpGet(string url, out string HttpWebResponseString, int timeout)
        {
            if (string.IsNullOrEmpty(url))
            {
                throw new ArgumentNullException("url");
            }
            HttpWebResponseString = "";
            try
            {
                HttpWebRequest httpWebRequest = WebRequest.Create(url) as HttpWebRequest;
                httpWebRequest.Method = "GET";
                httpWebRequest.ContentType = "application/x-www-form-urlencoded";
                httpWebRequest.UserAgent = DefaultUserAgent;
                httpWebRequest.Timeout = timeout;
                HttpWebResponse httpWebResponse = httpWebRequest.GetResponse() as HttpWebResponse;
                HttpWebResponseString = ReadHttpWebResponse(httpWebResponse);
                return true;
            }
            catch (Exception ex)
            {
                HttpWebResponseString = ex.ToString();
                return false;
            }
        }

        public static bool HttpPost(string url, byte[] Data, out string HttpWebResponseString, int timeout)
        {
            if (string.IsNullOrEmpty(url))
            {
                throw new ArgumentNullException("url");
            }
            HttpWebResponseString = "";
            HttpWebRequest httpWebRequest = null;
            Stream stream = null;
            try
            {
                httpWebRequest = (WebRequest.Create(url) as HttpWebRequest);
                httpWebRequest.Method = "POST";
                httpWebRequest.ContentType = "application/x-www-form-urlencoded";
                httpWebRequest.UserAgent = DefaultUserAgent;
                httpWebRequest.Timeout = timeout;
                if (Data != null)
                {
                    requestEncoding.GetString(Data);
                    stream = httpWebRequest.GetRequestStream();
                    stream.Write(Data, 0, Data.Length);
                }
                HttpWebResponse httpWebResponse = httpWebRequest.GetResponse() as HttpWebResponse;
                HttpWebResponseString = ReadHttpWebResponse(httpWebResponse);
                return true;
            }
            catch (Exception ex)
            {
                HttpWebResponseString = ex.ToString();
                return false;
            }
            finally
            {
                stream?.Close();
            }
        }

        /// <summary>
        /// 指定Post地址使用Get 方式获取全部字符串
        /// </summary>
        /// <param name="url">请求后台地址</param>
        /// <returns></returns>
        public static string Post(string url, Dictionary<string, string> dic)
        {
            string result = "";
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
            req.Method = "POST";
            req.ContentType = "application/x-www-form-urlencoded";
            #region 添加Post 参数
            StringBuilder builder = new StringBuilder();
            int i = 0;
            foreach (var item in dic)
            {
                if (i > 0)
                    builder.Append("&");
                builder.AppendFormat("{0}={1}", item.Key, item.Value);
                i++;
            }
            byte[] data = Encoding.UTF8.GetBytes(builder.ToString());
            req.ContentLength = data.Length;
            using (Stream reqStream = req.GetRequestStream())
            {
                reqStream.Write(data, 0, data.Length);
                reqStream.Close();
            }
            #endregion
            HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
            Stream stream = resp.GetResponseStream();
            //获取响应内容
            using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
            {
                result = reader.ReadToEnd();
            }
            return result;
        }

        public static string HttpPost(string url, IDictionary<string, string> parameters, string charset)
        {

            //StreamWriter sw = new StreamWriter(Application.StartupPath + @"/SyncUrl.log", true, System.Text.Encoding.GetEncoding("gb2312"));
            //sw.WriteLine(DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + @"  "  + url);
            //sw.Close(); sw.Dispose();

            HttpWebRequest req = GetWebRequest(url, "POST");
            req.ContentType = "application/json;charset=" + charset;
            
            string p = BuildQuery(parameters, charset);
            byte[] postData = Encoding.GetEncoding(charset).GetBytes(p);
            Stream reqStream = req.GetRequestStream();
            reqStream.Write(postData, 0, postData.Length);
            reqStream.Close();
            HttpWebResponse rsp = (HttpWebResponse)req.GetResponse();
            return GetResponseAsString(rsp, Encoding.UTF8);
        }

        public static string HttpPost(string url, IDictionary<string, string> parameters, string charset,string contentType)
        {

          

            HttpWebRequest req = GetWebRequest(url, "POST");
            req.ContentType = contentType;

            string p = BuildQuery(parameters, charset);
            byte[] postData = Encoding.GetEncoding(charset).GetBytes(p);
            Stream reqStream = req.GetRequestStream();
            reqStream.Write(postData, 0, postData.Length);
            reqStream.Close();
            HttpWebResponse rsp = (HttpWebResponse)req.GetResponse();
            return GetResponseAsString(rsp, Encoding.UTF8);
        }

        public static string Post(string url, IDictionary<string, string> parameters, string data, string apiToken = null)
        {
            if (parameters != null && parameters.Count > 0)
            {
                if (url.Contains("?"))
                {
                    url = url + "&" + BuildQuery(parameters);
                }
                else
                {
                    url = url + "?" + BuildQuery(parameters);
                }
            }

            HttpWebRequest req = GetWebRequest(url, "POST");
            req.ContentType = "application/json;charset=utf-8";
            if (!string.IsNullOrEmpty(apiToken))
            {
                req.Headers.Add("apiToken", apiToken);
            }

            byte[] postData = Encoding.UTF8.GetBytes(data);
            System.IO.Stream reqStream = req.GetRequestStream();
            reqStream.Write(postData, 0, postData.Length);
            reqStream.Close();

            HttpWebResponse rsp = (HttpWebResponse)req.GetResponse();
            return GetResponseAsString(rsp, Encoding.UTF8);
        }


        public static string sendPost(string url, string json)
        {
            System.IO.Stream stream = null;
            StreamReader reader = null;
            try
            {
                Encoding encoding = Encoding.UTF8;
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                request.Method = "POST";
                request.Accept = "text/html, application/xhtml+xml, */*";
                request.ContentType = "application/json";


                byte[] buffer = encoding.GetBytes(json);
                request.ContentLength = buffer.Length;
                request.GetRequestStream().Write(buffer, 0, buffer.Length);
                HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                using (reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
                { return reader.ReadToEnd(); }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                return "{\"FStatus\":0,\"FMsg\":'" + ex.Message + "'}";
            }
            finally
            {
                if (stream != null) stream.Close();
                if (reader != null) reader.Close();
            }
            return null;
        }

        private static HttpWebRequest GetWebRequest(string url, string method)
        {
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
            req.ServicePoint.Expect100Continue = false;
            req.Method = method;
            req.KeepAlive = true;
            req.UserAgent = "SEASHOP";
            req.Timeout = 300000;
            return req;
        }

        /// <summary>
        /// 把响应流转换为文本。
        /// </summary>
        /// <param name="rsp">响应流对象</param>
        /// <param name="encoding">编码方式</param>
        /// <returns>响应文本</returns>
        public static string GetResponseAsString(HttpWebResponse rsp, Encoding encoding)
        {
            StringBuilder result = new StringBuilder();
            Stream stream = null;
            StreamReader reader = null;

            try
            {
                // 以字符流的方式读取HTTP响应
                stream = rsp.GetResponseStream();
                reader = new StreamReader(stream, encoding);

                // 按字符读取并写入字符串缓冲
                int ch = -1;
                while ((ch = reader.Read()) > -1)
                {
                    // 过滤结束符
                    char c = (char)ch;
                    if (c != '\0')
                    {
                        result.Append(c);
                    }
                }
            }
            finally
            {
                // 释放资源
                if (reader != null) reader.Close();
                if (stream != null) stream.Close();
                if (rsp != null) rsp.Close();
            }

            return result.ToString();
        }

        /// <summary>
        /// 组装普通文本请求参数。
        /// </summary>
        /// <param name="parameters">Key-Value形式请求参数字典</param>
        /// <returns>URL编码后的请求数据</returns>
        public static string BuildQuery(IDictionary<string, string> parameters, string charset)
        {
            StringBuilder postData = new StringBuilder();
            bool hasParam = false;

            IEnumerator<KeyValuePair<string, string>> dem = parameters.GetEnumerator();
            while (dem.MoveNext())
            {
                string name = dem.Current.Key;
                string value = dem.Current.Value;
                // 忽略参数名或参数值为空的参数
                if (!string.IsNullOrEmpty(name) && !string.IsNullOrEmpty(value))
                {
                    if (hasParam)
                    {
                        postData.Append("&");
                    }

                    postData.Append(name);
                    postData.Append("=");

                    string encodedValue = HttpUtility.UrlEncode(value, Encoding.GetEncoding(charset));

                    postData.Append(encodedValue);
                    hasParam = true;
                }
            }

            return postData.ToString();
        }

        public static string ReadHttpWebResponse(HttpWebResponse HttpWebResponse)
        {
            Stream stream = null;
            StreamReader streamReader = null;
#pragma warning disable CS0219 // 变量“text”已被赋值，但从未使用过它的值
            string text = null;
#pragma warning restore CS0219 // 变量“text”已被赋值，但从未使用过它的值
            try
            {
                stream = HttpWebResponse.GetResponseStream();
                streamReader = new StreamReader(stream, Encoding.GetEncoding("utf-8"));
                return streamReader.ReadToEnd();
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                streamReader?.Close();
                stream?.Close();
                HttpWebResponse?.Close();
            }
        }

        public static string BuildQuery(IDictionary<string, string> parameters)
        {
            StringBuilder postData = new StringBuilder();
            bool hasParam = false;

            IEnumerator<KeyValuePair<string, string>> dem = parameters.GetEnumerator();
            while (dem.MoveNext())
            {
                string name = dem.Current.Key;
                string value = dem.Current.Value;
                // 忽略参数名或参数值为空的参数
                if (!string.IsNullOrEmpty(name) && !string.IsNullOrEmpty(value))
                {
                    if (hasParam)
                    {
                        postData.Append("&");
                    }

                    postData.Append(name);
                    postData.Append("=");
                    postData.Append(HttpUtility.UrlEncode(value, Encoding.UTF8));
                    hasParam = true;
                }
            }

            return postData.ToString();
        }
    }