后台请求帮助类

namespace BJSoft.WXYH.Common
{
    /// <summary>
    /// Http连接操作帮助类
    /// </summary>
    public class HttpHelper
    {
        #region 预定义方变量
        //默认的编码
        private Encoding encoding = Encoding.Default;
        //Post数据编码
        private Encoding postencoding = Encoding.Default;
        //HttpWebRequest对象用来发起请求
        private HttpWebRequest request = null;
        //获取影响流的数据对象
        private HttpWebResponse response = null;
        #endregion

        #region Public

        /// <summary>
        /// 根据相传入的数据，得到相应页面数据
        /// </summary>
        /// <param name="item">参数类对象</param>
        /// <returns>返回HttpResult类型</returns>
        public HttpResult GetHtml(HttpItem item)
        {
            //返回参数
            HttpResult result = new HttpResult();
            try
            {
                //准备参数
                SetRequest(item);
            }
            catch (Exception ex)
            {
                //配置参数时出错
                return new HttpResult() { Cookie = string.Empty, Header = null, Html = ex.Message, StatusDescription = "配置参数时出错：" + ex.Message };
            }
            try
            {
                //请求数据
                using (response = (HttpWebResponse)request.GetResponse())
                {
                    GetData(item, result);
                }
            }
            catch (WebException ex)
            {
                if (ex.Response != null)
                {
                    using (response = (HttpWebResponse)ex.Response)
                    {
                        GetData(item, result);
                    }
                }
                else
                {
                    result.Html = ex.Message;
                }
            }
            catch (Exception ex)
            {
                result.Html = ex.Message;
            }
            if (item.IsToLower) result.Html = result.Html.ToLower();
            return result;
        }
        #endregion

        #region GetData

        /// <summary>
        /// 获取数据的并解析的方法
        /// </summary>
        /// <param name="item"></param>
        /// <param name="result"></param>
        private void GetData(HttpItem item, HttpResult result)
        {
            #region base
            //获取StatusCode
            result.StatusCode = response.StatusCode;
            //获取StatusDescription
            result.StatusDescription = response.StatusDescription;
            //获取Headers
            result.Header = response.Headers;
            //获取最后访问的URl
            result.ResponseUri = response.ResponseUri.ToString();
            //获取CookieCollection
            if (response.Cookies != null) result.CookieCollection = response.Cookies;
            //获取set-cookie
            if (response.Headers["set-cookie"] != null) result.Cookie = response.Headers["set-cookie"];
            #endregion

            #region byte
            //处理网页Byte
            byte[] ResponseByte = GetByte();
            #endregion

            #region Html
            if (ResponseByte != null & ResponseByte.Length > 0)
            {
                //设置编码
                SetEncoding(item, result, ResponseByte);
                //得到返回的HTML
                result.Html = encoding.GetString(ResponseByte);
            }
            else
            {
                //没有返回任何Html代码
                result.Html = string.Empty;
            }
            #endregion
        }
        /// <summary>
        /// 设置编码
        /// </summary>
        /// <param name="item">HttpItem</param>
        /// <param name="result">HttpResult</param>
        /// <param name="ResponseByte">byte[]</param>
        private void SetEncoding(HttpItem item, HttpResult result, byte[] ResponseByte)
        {
            //是否返回Byte类型数据
            if (item.ResultType == ResultType.Byte) result.ResultByte = ResponseByte;
            //从这里开始我们要无视编码了
            if (encoding == null)
            {
                Match meta = Regex.Match(Encoding.Default.GetString(ResponseByte), "<meta[^<]*charset=([^<]*)[\"‘]", RegexOptions.IgnoreCase);
                string c = string.Empty;
                if (meta != null && meta.Groups.Count > 0)
                {
                    c = meta.Groups[1].Value.ToLower().Trim();
                }
                if (c.Length > 2)
                {
                    try
                    {
                        encoding = Encoding.GetEncoding(c.Replace("\"", string.Empty).Replace("‘", "").Replace(";", "").Replace("iso-8859-1", "gbk").Trim());
                    }
                    catch
                    {
                        if (string.IsNullOrEmpty(response.CharacterSet))
                        {
                            encoding = Encoding.UTF8;
                        }
                        else
                        {
                            encoding = Encoding.GetEncoding(response.CharacterSet);
                        }
                    }
                }
                else
                {
                    if (string.IsNullOrEmpty(response.CharacterSet))
                    {
                        encoding = Encoding.UTF8;
                    }
                    else
                    {
                        encoding = Encoding.GetEncoding(response.CharacterSet);
                    }
                }
            }
        }
        /// <summary>
        /// 提取网页Byte
        /// </summary>
        /// <returns></returns>
        private byte[] GetByte()
        {
            byte[] ResponseByte = null;
            using (MemoryStream _stream = new MemoryStream())
            {
                //GZIIP处理
                if (response.ContentEncoding != null && response.ContentEncoding.Equals("gzip", StringComparison.InvariantCultureIgnoreCase))
                {
                    //开始读取流并设置编码方式
                    new GZipStream(response.GetResponseStream(), CompressionMode.Decompress).CopyTo(_stream, 10240);
                }
                else
                {
                    //开始读取流并设置编码方式
                    response.GetResponseStream().CopyTo(_stream, 10240);
                }
                //获取Byte
                ResponseByte = _stream.ToArray();
            }
            return ResponseByte;
        }
        #endregion

        #region SetRequest

        /// <summary>
        /// 为请求准备参数
        /// </summary>
        ///<param name="item">参数列表</param>
        private void SetRequest(HttpItem item)
        {
            // 验证证书
            SetCer(item);
            //设置Header参数
            if (item.Header != null && item.Header.Count > 0) foreach (string key in item.Header.AllKeys)
                {
                    request.Headers.Add(key, item.Header[key]);
                }
            // 设置代理
            SetProxy(item);
            if (item.ProtocolVersion != null) request.ProtocolVersion = item.ProtocolVersion;
            request.ServicePoint.Expect100Continue = item.Expect100Continue;
            //请求方式Get或者Post
            request.Method = item.Method;
            request.Timeout = item.Timeout;
            request.KeepAlive = item.KeepAlive;
            request.ReadWriteTimeout = item.ReadWriteTimeout;
            if (!string.IsNullOrWhiteSpace(item.Host))
            {
                request.Host = item.Host;
            }
            if (item.IfModifiedSince != null) request.IfModifiedSince = Convert.ToDateTime(item.IfModifiedSince);
            //Accept
            request.Accept = item.Accept;
            //ContentType返回类型
            request.ContentType = item.ContentType;
            //UserAgent客户端的访问类型，包括浏览器版本和操作系统信息
            request.UserAgent = item.UserAgent;
            // 编码
            encoding = item.Encoding;
            //设置安全凭证
            request.Credentials = item.ICredentials;
            //设置Cookie
            SetCookie(item);
            //来源地址
            request.Referer = item.Referer;
            //是否执行跳转功能
            request.AllowAutoRedirect = item.Allowautoredirect;
            if (item.MaximumAutomaticRedirections > 0)
            {
                request.MaximumAutomaticRedirections = item.MaximumAutomaticRedirections;
            }
            //设置Post数据
            SetPostData(item);
            //设置最大连接
            if (item.Connectionlimit > 0) request.ServicePoint.ConnectionLimit = item.Connectionlimit;
        }
        /// <summary>
        /// 设置证书
        /// </summary>
        /// <param name="item"></param>
        private void SetCer(HttpItem item)
        {
            if (!string.IsNullOrWhiteSpace(item.CerPath))
            {
                //这一句一定要写在创建连接的前面。使用回调的方法进行证书验证。
                ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback(CheckValidationResult);
                //初始化对像，并设置请求的URL地址
                request = (HttpWebRequest)WebRequest.Create(item.URL);
                SetCerList(item);
                //将证书添加到请求里
                request.ClientCertificates.Add(new X509Certificate(item.CerPath));
            }
            else
            {
                //初始化对像，并设置请求的URL地址
                request = (HttpWebRequest)WebRequest.Create(item.URL);
                SetCerList(item);
            }
        }
        /// <summary>
        /// 设置多个证书
        /// </summary>
        /// <param name="item"></param>
        private void SetCerList(HttpItem item)
        {
            if (item.ClentCertificates != null && item.ClentCertificates.Count > 0)
            {
                foreach (X509Certificate c in item.ClentCertificates)
                {
                    request.ClientCertificates.Add(c);
                }
            }
        }
        /// <summary>
        /// 设置Cookie
        /// </summary>
        /// <param name="item">Http参数</param>
        private void SetCookie(HttpItem item)
        {
            if (!string.IsNullOrEmpty(item.Cookie)) request.Headers[HttpRequestHeader.Cookie] = item.Cookie;
            //设置CookieCollection
            if (item.ResultCookieType == ResultCookieType.CookieCollection)
            {
                request.CookieContainer = new CookieContainer();
                if (item.CookieCollection != null && item.CookieCollection.Count > 0)
                    request.CookieContainer.Add(item.CookieCollection);
            }
        }
        /// <summary>
        /// 设置Post数据
        /// </summary>
        /// <param name="item">Http参数</param>
        private void SetPostData(HttpItem item)
        {
            //验证在得到结果时是否有传入数据
            if (!request.Method.Trim().ToLower().Contains("get"))
            {
                if (item.PostEncoding != null)
                {
                    postencoding = item.PostEncoding;
                }
                byte[] buffer = null;
                //写入Byte类型
                if (item.PostDataType == PostDataType.Byte && item.PostdataByte != null && item.PostdataByte.Length > 0)
                {
                    //验证在得到结果时是否有传入数据
                    buffer = item.PostdataByte;
                }//写入文件
                else if (item.PostDataType == PostDataType.FilePath && !string.IsNullOrWhiteSpace(item.Postdata))
                {
                    StreamReader r = new StreamReader(item.Postdata, postencoding);
                    buffer = postencoding.GetBytes(r.ReadToEnd());
                    r.Close();
                } //写入字符串
                else if (!string.IsNullOrWhiteSpace(item.Postdata))
                {
                    buffer = postencoding.GetBytes(item.Postdata);
                }
                if (buffer != null)
                {
                    request.ContentLength = buffer.Length;
                    request.GetRequestStream().Write(buffer, 0, buffer.Length);
                }
            }
        }
        /// <summary>
        /// 设置代理
        /// </summary>
        /// <param name="item">参数对象</param>
        private void SetProxy(HttpItem item)
        {
            bool isIeProxy = false;
            if (!string.IsNullOrWhiteSpace(item.ProxyIp))
            {
                isIeProxy = item.ProxyIp.ToLower().Contains("ieproxy");
            }
            if (!string.IsNullOrWhiteSpace(item.ProxyIp) && !isIeProxy)
            {
                //设置代理服务器
                if (item.ProxyIp.Contains(":"))
                {
                    string[] plist = item.ProxyIp.Split(‘:‘);
                    WebProxy myProxy = new WebProxy(plist[0].Trim(), Convert.ToInt32(plist[1].Trim()));
                    //建议连接
                    myProxy.Credentials = new NetworkCredential(item.ProxyUserName, item.ProxyPwd);
                    //给当前请求对象
                    request.Proxy = myProxy;
                }
                else
                {
                    WebProxy myProxy = new WebProxy(item.ProxyIp, false);
                    //建议连接
                    myProxy.Credentials = new NetworkCredential(item.ProxyUserName, item.ProxyPwd);
                    //给当前请求对象
                    request.Proxy = myProxy;
                }
            }
            else if (isIeProxy)
            {
                //设置为IE代理
            }
            else
            {
                request.Proxy = item.WebProxy;
            }
        }
        #endregion

        #region private main
        /// <summary>
        /// 回调验证证书问题
        /// </summary>
        /// <param name="sender">流对象</param>
        /// <param name="certificate">证书</param>
        /// <param name="chain">X509Chain</param>
        /// <param name="errors">SslPolicyErrors</param>
        /// <returns>bool</returns>
        private bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors) { return true; }
        #endregion
    }

    #region public calss
    /// <summary>
    /// Http请求参考类
    /// </summary>
    public class HttpItem
    {
        /// <summary>
        /// 请求URL必须填写
        /// </summary>
        public string URL { get; set; }
        string _Method = "GET";
        /// <summary>
        /// 请求方式默认为GET方式,当为POST方式时必须设置Postdata的值
        /// </summary>
        public string Method
        {
            get { return _Method; }
            set { _Method = value; }
        }
        int _Timeout = 100000;
        /// <summary>
        /// 默认请求超时时间
        /// </summary>
        public int Timeout
        {
            get { return _Timeout; }
            set { _Timeout = value; }
        }
        int _ReadWriteTimeout = 30000;
        /// <summary>
        /// 默认写入Post数据超时间
        /// </summary>
        public int ReadWriteTimeout
        {
            get { return _ReadWriteTimeout; }
            set { _ReadWriteTimeout = value; }
        }
        /// <summary>
        /// 设置Host的标头信息
        /// </summary>
        public string Host { get; set; }
        Boolean _KeepAlive = true;
        /// <summary>
        ///  获取或设置一个值，该值指示是否与 Internet 资源建立持久性连接默认为true。
        /// </summary>
        public Boolean KeepAlive
        {
            get { return _KeepAlive; }
            set { _KeepAlive = value; }
        }
        string _Accept = "text/html, application/xhtml+xml, */*";
        /// <summary>
        /// 请求标头值 默认为text/html, application/xhtml+xml, */*
        /// </summary>
        public string Accept
        {
            get { return _Accept; }
            set { _Accept = value; }
        }
        string _ContentType = "text/html";
        /// <summary>
        /// 请求返回类型默认 text/html
        /// </summary>
        public string ContentType
        {
            get { return _ContentType; }
            set { _ContentType = value; }
        }
        string _UserAgent = "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)";
        /// <summary>
        /// 客户端访问信息默认Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
        /// </summary>
        public string UserAgent
        {
            get { return _UserAgent; }
            set { _UserAgent = value; }
        }
        /// <summary>
        /// 返回数据编码默认为NUll,可以自动识别,一般为utf-8,gbk,gb2312
        /// </summary>
        public Encoding Encoding { get; set; }
        private PostDataType _PostDataType = PostDataType.String;
        /// <summary>
        /// Post的数据类型
        /// </summary>
        public PostDataType PostDataType
        {
            get { return _PostDataType; }
            set { _PostDataType = value; }
        }
        /// <summary>
        /// Post请求时要发送的字符串Post数据
        /// </summary>
        public string Postdata { get; set; }
        /// <summary>
        /// Post请求时要发送的Byte类型的Post数据
        /// </summary>
        public byte[] PostdataByte { get; set; }
        /// <summary>
        /// Cookie对象集合
        /// </summary>
        public CookieCollection CookieCollection { get; set; }
        /// <summary>
        /// 请求时的Cookie
        /// </summary>
        public string Cookie { get; set; }
        /// <summary>
        /// 来源地址，上次访问地址
        /// </summary>
        public string Referer { get; set; }
        /// <summary>
        /// 证书绝对路径
        /// </summary>
        public string CerPath { get; set; }
        /// <summary>
        /// 设置代理对象，不想使用IE默认配置就设置为Null，而且不要设置ProxyIp
        /// </summary>
        public WebProxy WebProxy { get; set; }
        private Boolean isToLower = false;
        /// <summary>
        /// 是否设置为全文小写，默认为不转化
        /// </summary>
        public Boolean IsToLower
        {
            get { return isToLower; }
            set { isToLower = value; }
        }
        private Boolean allowautoredirect = false;
        /// <summary>
        /// 支持跳转页面，查询结果将是跳转后的页面，默认是不跳转
        /// </summary>
        public Boolean Allowautoredirect
        {
            get { return allowautoredirect; }
            set { allowautoredirect = value; }
        }
        private int connectionlimit = 1024;
        /// <summary>
        /// 最大连接数
        /// </summary>
        public int Connectionlimit
        {
            get { return connectionlimit; }
            set { connectionlimit = value; }
        }
        /// <summary>
        /// 代理Proxy 服务器用户名
        /// </summary>
        public string ProxyUserName { get; set; }
        /// <summary>
        /// 代理 服务器密码
        /// </summary>
        public string ProxyPwd { get; set; }
        /// <summary>
        /// 代理 服务IP,如果要使用IE代理就设置为ieproxy
        /// </summary>
        public string ProxyIp { get; set; }
        private ResultType resulttype = ResultType.String;
        /// <summary>
        /// 设置返回类型String和Byte
        /// </summary>
        public ResultType ResultType
        {
            get { return resulttype; }
            set { resulttype = value; }
        }
        private WebHeaderCollection header = new WebHeaderCollection();
        /// <summary>
        /// header对象
        /// </summary>
        public WebHeaderCollection Header
        {
            get { return header; }
            set { header = value; }
        }
        /// <summary>
        //     获取或设置用于请求的 HTTP 版本。返回结果:用于请求的 HTTP 版本。默认为 System.Net.HttpVersion.Version11。
        /// </summary>
        public Version ProtocolVersion { get; set; }
        private Boolean _expect100continue = true;
        /// <summary>
        ///  获取或设置一个 System.Boolean 值，该值确定是否使用 100-Continue 行为。如果 POST 请求需要 100-Continue 响应，则为 true；否则为 false。默认值为 true。
        /// </summary>
        public Boolean Expect100Continue
        {
            get { return _expect100continue; }
            set { _expect100continue = value; }
        }
        /// <summary>
        /// 设置509证书集合
        /// </summary>
        public X509CertificateCollection ClentCertificates { get; set; }
        /// <summary>
        /// 设置或获取Post参数编码,默认的为Default编码
        /// </summary>
        public Encoding PostEncoding { get; set; }
        private ResultCookieType _ResultCookieType = ResultCookieType.String;
        /// <summary>
        /// Cookie返回类型,默认的是只返回字符串类型
        /// </summary>
        public ResultCookieType ResultCookieType
        {
            get { return _ResultCookieType; }
            set { _ResultCookieType = value; }
        }
        private ICredentials _ICredentials = CredentialCache.DefaultCredentials;
        /// <summary>
        /// 获取或设置请求的身份验证信息。
        /// </summary>
        public ICredentials ICredentials
        {
            get { return _ICredentials; }
            set { _ICredentials = value; }
        }
        /// <summary>
        /// 设置请求将跟随的重定向的最大数目
        /// </summary>
        public int MaximumAutomaticRedirections { get; set; }
        private DateTime? _IfModifiedSince = null;
        /// <summary>
        /// 获取和设置IfModifiedSince，默认为当前日期和时间
        /// </summary>
        public DateTime? IfModifiedSince
        {
            get { return _IfModifiedSince; }
            set { _IfModifiedSince = value; }
        }

    }
    /// <summary>
    /// Http返回参数类
    /// </summary>
    public class HttpResult
    {
        /// <summary>
        /// Http请求返回的Cookie
        /// </summary>
        public string Cookie { get; set; }
        /// <summary>
        /// Cookie对象集合
        /// </summary>
        public CookieCollection CookieCollection { get; set; }
        private string _html = string.Empty;
        /// <summary>
        /// 返回的String类型数据 只有ResultType.String时才返回数据，其它情况为空
        /// </summary>
        public string Html
        {
            get { return _html; }
            set { _html = value; }
        }
        /// <summary>
        /// 返回的Byte数组 只有ResultType.Byte时才返回数据，其它情况为空
        /// </summary>
        public byte[] ResultByte { get; set; }
        /// <summary>
        /// header对象
        /// </summary>
        public WebHeaderCollection Header { get; set; }
        /// <summary>
        /// 返回状态说明
        /// </summary>
        public string StatusDescription { get; set; }
        /// <summary>
        /// 返回状态码,默认为OK
        /// </summary>
        public HttpStatusCode StatusCode { get; set; }
        /// <summary>
        /// 最后访问的URl
        /// </summary>
        public string ResponseUri { get; set; }
        /// <summary>
        /// 获取重定向的URl
        /// </summary>
        public string RedirectUrl
        {
            get
            {
                try
                {
                    if (Header != null && Header.Count > 0)
                    {
                        if (Header.AllKeys.Any(k => k.ToLower().Contains("location")))
                        {
                            string locationurl = Header["location"].ToString().ToLower();

                            if (!string.IsNullOrWhiteSpace(locationurl))
                            {
                                bool b = locationurl.StartsWith("http://") || locationurl.StartsWith("https://");
                                if (!b)
                                {
                                    locationurl = new Uri(new Uri(ResponseUri), locationurl).AbsoluteUri;
                                }
                            }
                            return locationurl;
                        }
                    }
                }
                catch { }
                return string.Empty;
            }
        }
    }
    /// <summary>
    /// 返回类型
    /// </summary>
    public enum ResultType
    {
        /// <summary>
        /// 表示只返回字符串 只有Html有数据
        /// </summary>
        String,
        /// <summary>
        /// 表示返回字符串和字节流 ResultByte和Html都有数据返回
        /// </summary>
        Byte
    }
    /// <summary>
    /// Post的数据格式默认为string
    /// </summary>
    public enum PostDataType
    {
        /// <summary>
        /// 字符串类型，这时编码Encoding可不设置
        /// </summary>
        String,
        /// <summary>
        /// Byte类型，需要设置PostdataByte参数的值编码Encoding可设置为空
        /// </summary>
        Byte,
        /// <summary>
        /// 传文件，Postdata必须设置为文件的绝对路径，必须设置Encoding的值
        /// </summary>
        FilePath
    }
    /// <summary>
    /// Cookie返回类型
    /// </summary>
    public enum ResultCookieType
    {
        /// <summary>
        /// 只返回字符串类型的Cookie
        /// </summary>
        String,
        /// <summary>
        /// CookieCollection格式的Cookie集合同时也返回String类型的cookie
        /// </summary>
        CookieCollection
    }
    #endregion
}

//使用方法
       string url = "https://api.youku.com/oauth2/token.json";
                        var now = DateTime.Now;
                        HttpHelper h = new HttpHelper();
                        var result = h.GetHtml(new HttpItem
                        {
                            URL = url,
                            Method = "POST",
                            ContentType = "application/x-www-form-urlencoded",
                            Postdata = "client_id=" + client.CLIENT_ID + "&grant_type=refresh_token&refresh_token=" + client.REFRESH_TOKEN
                        }).Html;

原文地址：https://www.cnblogs.com/stubborn-donkey/p/11646210.html