.net core运用application/x-www-form-urlencoded发起post请求

通常情况下都是使用 application/json发起post请求，但是有的.net 接口只接收 application/x-www-form-urlencoded

例如：

{
　　name:"张三",
　　results:[
　　　　{score:88,subject:"语文"}
　　]
}

需改为 name=张三&results[0][score]=88&results[0][subject]=语文方式

对常规的post请求进行处理，把json转为urlencoded

    /// <summary>
        /// 发起POST同步请求
        /// </summary>
        /// <param name="url"></param>
        /// <param name="postData"></param>
        /// <param name="contentType">application/xml、application/json、application/text、application/x-www-form-urlencoded</param>
        /// <param name="headers">填充消息头</param>        
        /// <returns></returns>
        public static string HttpPost(string url, string postData = null, Dictionary<string, string> headers = null, string contentType = "application/json", int timeOut = 30)
        {
            postData = postData ?? "";
            if (contentType == "application/x-www-form-urlencoded")
            {
                postData = JsonUrlEncode(postData);
            }
            using (HttpClient client = new HttpClient())
            {
                if (headers != null)
                {
                    foreach (var header in headers)
                        client.DefaultRequestHeaders.Add(header.Key, header.Value);
                }
                using (HttpContent httpContent = new StringContent(postData, Encoding.UTF8))
                {
                    if (contentType != null)
                        httpContent.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue(contentType);

                    HttpResponseMessage response = client.PostAsync(url, httpContent).Result;
                    return response.Content.ReadAsStringAsync().Result;
                }
            }
        }

以下为json转urlencoded的方法和地柜

  /// <summary>
        /// json转urlencode
        /// </summary>
        /// <returns></returns>
        public static string JsonUrlEncode(string json)
        {
            Dictionary<string, object> dic = JsonConvert.DeserializeObject<Dictionary<string, object>>(json);
            StringBuilder builder = new StringBuilder();
            foreach (KeyValuePair<string, object> item in dic)
            {
                builder.Append(GetFormDataContent(item, ""));
            }
            return builder.ToString().TrimEnd('&');
        }

        /// <summary>
        /// 递归转formdata
        /// </summary>
        /// <param name="item"></param>
        /// <param name="preStr"></param>
        /// <returns></returns>
        private static string GetFormDataContent(KeyValuePair<string, object> item, string preStr)
        {
            StringBuilder builder = new StringBuilder();
            if (string.IsNullOrEmpty(item.Value?.ToString()))
            {
                builder.AppendFormat("{0}={1}", string.IsNullOrEmpty(preStr) ? item.Key : (preStr + "[" + item.Key + "]"), System.Web.HttpUtility.UrlEncode((item.Value == null ? "" : item.Value.ToString()).ToString()));
                builder.Append("&");
            }
            else
            {
                //如果是数组
                if (item.Value.GetType().Name.Equals("JArray"))
                {
                    var children = JsonConvert.DeserializeObject<List<object>>(item.Value.ToString());
                    for (int j = 0; j < children.Count; j++)
                    {
                        Dictionary<string, object> childrendic = JsonConvert.DeserializeObject<Dictionary<string, object>>(JsonConvert.SerializeObject(children[j]));
                        foreach (var row in childrendic)
                        {
                            builder.Append(GetFormDataContent(row, string.IsNullOrEmpty(preStr) ? (item.Key + "[" + j + "]") : (preStr + "[" + item.Key + "][" + j + "]")));
                        }
                    }

                }
                //如果是对象
                else if (item.Value.GetType().Name.Equals("JObject"))
                {
                    Dictionary<string, object> children = JsonConvert.DeserializeObject<Dictionary<string, object>>(item.Value.ToString());
                    foreach (var row in children)
                    {
                        builder.Append(GetFormDataContent(row, string.IsNullOrEmpty(preStr) ? item.Key : (preStr + "[" + item.Key + "]")));
                    }
                }
                //字符串、数字等
                else
                {
                    builder.AppendFormat("{0}={1}", string.IsNullOrEmpty(preStr) ? item.Key : (preStr + "[" + item.Key + "]"), System.Web.HttpUtility.UrlEncode((item.Value == null ? "" : item.Value.ToString()).ToString()));
                    builder.Append("&");
                }
            }

            return builder.ToString();
        }