form-urlencoded转json

 url参数转json，先转为键值对，再转json 需要用到Newtonsoft.Json

   public string ConvertJson(string str)
        {
            Dictionary<string, string> dic = new Dictionary<string, string>();
            Regex re = new Regex(@"(^|&)?(\w+)=([^&]+)(&|$)?", RegexOptions.Compiled);
            MatchCollection mc = re.Matches(str);
            foreach (Match m in mc)
            {
                dic.Add(m.Result("$2"), m.Result("$3"));
            }

            string json = JsonConvert.SerializeObject(dic);
            return json;
        }

有url时，url中的&符号需要替换下，不然会出问题