/// <summary>
    /// Json.net默认转换设置
    /// </summary>
    private static void DefaultJsonConvertSetting()
    {
      JsonSerializerSettings setting = new JsonSerializerSettings();
      JsonConvert.DefaultSettings = new Func<JsonSerializerSettings>(() =>
      {
        //日期类型默认格式化处理
        setting.DateFormatHandling = DateFormatHandling.MicrosoftDateFormat;
        setting.DateFormatString = "yyyy-MM-dd HH:mm:ss";

        //空值处理
        //setting.NullValueHandling = NullValueHandling.Ignore;

        return setting;
      });
    }

IsoDateTimeConverter timeFormat = new IsoDateTimeConverter();
      timeFormat.DateTimeFormat = "yyyy-MM-dd HH:mm:ss";
      JsonConvert.SerializeObject(stu, Newtonsoft.Json.Formatting.Indented, timeFormat);

public class student
  {
    public string Name { get; set; }
    public int Age { get; set; }
    [JsonConverter(typeof(DateFormat))]
    public DateTime BirthDay { get; set; }
    [JsonConverter(typeof(DateTimeFormat))]
    public DateTime CreateTime { get; set; }
  }
  public class DateFormat:IsoDateTimeConverter
  {
    public DateFormat()
    {
      base.DateTimeFormat = "yyyy-MM-dd";
    }
  }
  public class DateTimeFormat:IsoDateTimeConverter
  {
    public DateTimeFormat()
    {
      base.DateTimeFormat = "yyyy-MM-dd HH:mm:ss";
    }
  }

student stu = new student()
       {
         Name = "张三",
         Age = ,
         BirthDay = new DateTime(, , ),
         CreateTime = DateTime.Now
       };
       string result = JsonConvert.SerializeObject(stu);

result = {"Name":"张三","Age":30,"BirthDay":"1986-07-16","CreateTime":"2016-01-16 23:13:34"}