//using System.Web.Script.Serialization;

JavaScriptSerializer serializer = new JavaScriptSerializer();

Dictionary<string, object> json = (Dictionary<string, object>)serializer.DeserializeObject(

    "{name: 'zswang', forum: 'c#'}");

object value;

if (json.TryGetValue("name", out value))

 string value2 = json.Where(t => t.Key == "access_token").FirstOrDefault().Value;

    Console.WriteLine(value); // 输出:zswang