IDictionary<string, object> map = new Dictionary<string, object>();
map["taxpayerNum"] = "110101201702071";
map["enterpriseName"] = "测试新1";
map["tradeNo"] = prefix + "20000344";
map["tradeTime"] = "2018-04-28 09:15:54";
// map.put("mergeTradeNo", "1");
map["casherName"] = "";
map["reviewerName"] = "";
map["drawerName"] = "";
IList<IDictionary<string, string>> _content = new List<IDictionary<string, string>>();
IDictionary<string, string> _contentlist = new Dictionary<string, string>();
_contentlist["taxpayerNum"] = "12345";
_contentlist["enterpriseName"] = "测试";
_contentlist["legalPersonName"] = "测试法人";
_contentlist["contactsName"] = "测试联系人";
_contentlist["contactsEmail"] = "123456@qq.com";
_contentlist["contactsPhone"] = "150123456780";
_contentlist["regionCode"] = "22";
_contentlist["cityName"] = "测试城市";
_contentlist["enterpriseAddress"] = "测试地址";
_contentlist["taxRegistrationCertificate"] = "data:image/png;base64,mCC";
_content.Add(_contentlist);
map["content"] = _content;
string content = Newtonsoft.Json.JsonConvert.SerializeObject(map);

解析JSON用这个方法

string retString = " {\"companyID\":\"15\",\"employees\":[{\"firstName\":\"Bill\",\"lastName\":\"Gates\"},{\"firstName\":\"George\",\"lastName\":\"Bush\"}],\"manager\":[{\"salary\":\"6000\",\"age\":\"23\"},{\"salary\":\"8000\",\"age\":\"26\"}]} ";
//解析josn

JObject jo = JObject.Parse(retString);

Console.WriteLine(jo["employees"][1]["firstName"].ToString());