服务端发post请求产生的编码问题

最近在做一个功能，大概功能是这样的，供应商提供http接口给我们，然后我们抓取供应商的数据保存到数据库，问题在于他们编码格式是gb2312的，而我们是utf-8。

大家可能会有个误区，post请求是无需编码的，其实不然，只要在http请求头中 "Content-Type"为"application/x-www-form-urlencoded，调接口前都会用当前编码格式urlencode。所以如果前端post数据到后端时，前端是gb2312编码格式，后端是utf-8，只需在Content-Type中设置，application/x-www-form-urlencoded;charset=utf-8。

而我们是服务端直接调接口，而我用的是restsharp

var request = new RestRequest(Method.POST);

request.RequestFormat = DataFormat.Json;
request.AddBody(model);

var client = new RestClient("http://localhost:2290/Interface/Index");

var response = client.Execute(request);
return response.Content;

翻阅文档，这期间会自动urlencode。。。

后来尝试设置web.config，设置默认编码格式，编码问题依然解决不了，有种冲动想去看restsharp的源码，可惜时间来不及啊。。。。（有时间一定要看下）

<globalization requestEncoding="gb2312" responseEncoding="gb2312"/>

最后终于找到了解决方案，用.net 源生的方式 httprequest 

        /// <summary>  
        /// 创建POST方式的HTTP请求  
        /// </summary>  
        /// <param name="url">请求的URL</param>  
        /// <param name="parameters">随同请求POST的参数名称及参数值字典</param>  
        /// <param name="timeout">请求的超时时间</param>  
        /// <param name="userAgent">请求的客户端浏览器信息，可以为空</param>  
        /// <param name="requestEncoding">发送HTTP请求时所用的编码</param>  
        /// <param name="cookies">随同HTTP请求发送的Cookie信息，如果不需要身份验证可以为空</param>  
        /// <returns></returns>  
        public static HttpWebResponse CreatePostHttpResponse(string url, IDictionary<string, string> parameters, int? timeout, string userAgent, Encoding requestEncoding, CookieCollection cookies)
        {
            if (string.IsNullOrEmpty(url))
            {
                throw new ArgumentNullException("url");
            }
            if (requestEncoding == null)
            {
                throw new ArgumentNullException("requestEncoding");
            }
            HttpWebRequest request = null;
            //如果是发送HTTPS请求  
            if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
            {
                ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
                request = WebRequest.Create(url) as HttpWebRequest;
                request.ProtocolVersion = HttpVersion.Version10;
            }
            else
            {
                request = WebRequest.Create(url) as HttpWebRequest;
            }
            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";

            if (!string.IsNullOrEmpty(userAgent))
            {
                request.UserAgent = userAgent;
            }
            else
            {
                request.UserAgent = DefaultUserAgent;
            }

            if (timeout.HasValue)
            {
                request.Timeout = timeout.Value;
            }
            if (cookies != null)
            {
                request.CookieContainer = new CookieContainer();
                request.CookieContainer.Add(cookies);
            }
            //如果需要POST数据  
            if (!(parameters == null || parameters.Count == 0))
            {
                StringBuilder buffer = new StringBuilder();
                int i = 0;
                foreach (string key in parameters.Keys)
                {
                    if (i > 0)
                    {
                        buffer.AppendFormat("&{0}={1}", key, parameters[key]);
                    }
                    else
                    {
                        buffer.AppendFormat("{0}={1}", key, parameters[key]);
                    }
                    i++;
                }
                byte[] data = requestEncoding.GetBytes(buffer.ToString());
                using (Stream stream = request.GetRequestStream())
                {
                    stream.Write(data, 0, data.Length);
                }
            }
            return request.GetResponse() as HttpWebResponse;
        }

调用如下：

            IDictionary<string, string> parameters = new Dictionary<string, string>();
            parameters.Add("RequestJson", jsonstr);

            HttpWebResponse response = HttpWebResponseUtility.CreatePostHttpResponse(url, parameters, null, null, Encoding.GetEncoding("GB2312"), null);

            using (StreamReader reader = new StreamReader(response.GetResponseStream(), System.Text.Encoding.UTF8))
            {
                strres = reader.ReadToEnd();
            }