using Newtonsoft.Json;//引用命名空间

Dictionary<string, string> Content = new Dictionary<string, string>();
Content.Add("bulletinContent", "this is bulletinContent");
 Content.Add("topToDay", "this is topToDay");

//Dictionary转json
 string Contentjson = JsonConvert.SerializeObject(Content);
//json转Dictionary
Dictionary<string, string> DicContent = (Dictionary<string, string>)JsonConvert.DeserializeObject(Contentjson.ToString());