public static  class JsonHelper

    {

        static JsonHelper()

        {

            Newtonsoft.Json.JsonSerializerSettings setting = new Newtonsoft.Json.JsonSerializerSettings();

            JsonConvert.DefaultSettings = new Func<JsonSerializerSettings>(() =>

            {

                //日期类型默认格式化处理

                setting.DateFormatHandling = Newtonsoft.Json.DateFormatHandling.MicrosoftDateFormat;

                setting.DateFormatString = "yyyy-MM-dd HH:mm:ss";

                //空值处理

                setting.NullValueHandling = NullValueHandling.Ignore;

                //高级用法九中的Bool类型转换 设置

                //setting.Converters.Add(new BoolConvert("是,否"));

                if (setting.Converters.FirstOrDefault(p=>p.GetType()==typeof(JsonCustomDoubleConvert))==null)

                {

                    setting.Converters.Add(new JsonCustomDoubleConvert());

                }

                return setting;

            });

        }

        public static String ToJsonStr<T>(this T obj) where T : class

        {

            if (obj == null)

                return string.Empty;

            return JsonConvert.SerializeObject(obj, Formatting.Indented);

        }

        public static T ToInstance<T>(this String jsonStr) where T : class

        {

            if (string.IsNullOrEmpty(jsonStr))

                return null;

            try

            {

                var instance = JsonConvert.DeserializeObject<T>(jsonStr);

                return instance;

            }

            catch

            {

                return null;

            }

        }

    }

    /// <summary>

    /// 自定义数值类型序列化转换器(默认保留3位)

    /// </summary>

    public class JsonCustomDoubleConvert : CustomCreationConverter<double>

    {

        /// <summary>

        /// 序列化后保留小数位数

        /// </summary>

        public virtual int Digits { get;private set; }

        /// <summary>

        /// .ctor

        /// </summary>

        public JsonCustomDoubleConvert()

        {

            this.Digits = ;

        }

        /// <summary>

        /// .ctor

        /// </summary>

        /// <param name="digits">序列化后保留小数位数</param>

        public JsonCustomDoubleConvert(int digits)

        {

            this.Digits = digits;

        }

        /// <summary>

        /// 重载是否可写

        /// </summary>

        public override bool CanWrite { get { return true; } }

        /// <summary>

        /// 重载创建方法

        /// </summary>

        /// <param name="objectType"></param>

        /// <returns></returns>

        public override double Create(Type objectType)

        {

            return 0.0;

        }

        /// <summary>

        /// 重载序列化方法

        /// </summary>

        /// <param name="writer"></param>

        /// <param name="value"></param>

        /// <param name="serializer"></param>

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)

        {

            if (value == null)

            {

                writer.WriteNull();

            }

            else

            {

                var formatter = ((double)value).ToString("N" + Digits.ToString());

                writer.WriteValue(formatter);

            }

        }

    }

    /// <summary>

    /// 自定义数值类型序列化转换器(无小数位)

    /// </summary>

    public class JsonCustomDoubleWith0DigitsConvert : JsonCustomDoubleConvert

    {

        public override int Digits

        {

            get { return ; }

        }

    }

    /// <summary>

    /// 自定义数值类型序列化转换器(保留1位)

    /// </summary>

    public class JsonCustomDoubleWith1DigitsConvert : JsonCustomDoubleConvert

    {

        public override int Digits

        {

            get { return ; }

        }

    }

    /// <summary>

    /// 自定义数值类型序列化转换器(保留2位)

    /// </summary>

    public class JsonCustomDoubleWith2DigitsConvert : JsonCustomDoubleConvert

    {

        public override int Digits

        {

            get { return ; }

        }

    }

    /// <summary>

    /// 自定义数值类型序列化转换器(保留3位)

    /// </summary>

    public class JsonCustomDoubleWith3DigitsConvert : JsonCustomDoubleConvert

    {

        public override int Digits

        {

            get { return ; }

        }

    }

    /// <summary>

    /// 自定义数值类型序列化转换器(保留4位)

    /// </summary>

    public class JsonCustomDoubleWith4DigitsConvert : JsonCustomDoubleConvert

    {

        public override int Digits

        {

            get { return ; }

        }

    }

    /// <summary>

    /// 自定义数值类型序列化转换器(保留5位)

    /// </summary>

    public class JsonCustomDoubleWith5DigitsConvert : JsonCustomDoubleConvert

    {

        public override int Digits

        {

            get { return ; }

        }

    }

    class Order

    {

        public int Id { get; set; }

        public static int OrderId = GetOrderId();

        public IEnumerable<int> Missions = null;

        static int GetOrderId()

        {

            return new Random().Next(, );

        }

        [JsonConverter(typeof(JsonCustomDoubleWith0DigitsConvert))]

        public double OrderAmount { get; set; }

    }