asp.net webapi Datetime 序列化反序列化为时间戳

项目需求原因需要把Webapi中的Datetime 序列化及反序列化时间戳(long)，遇到相同问题的同学可作参考。

1.声明一个时间戳转换器

    public class UnixDateTimeConvertor : DateTimeConverterBase
    {

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            long jsTimeStamp = long.Parse(reader.Value.ToString());
            System.DateTime startTime = TimeZone.CurrentTimeZone.ToLocalTime(new System.DateTime(1970, 1, 1));
            DateTime dt = startTime.AddMilliseconds(jsTimeStamp);
            return dt;
        }

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            System.DateTime startTime = TimeZone.CurrentTimeZone.ToLocalTime(new System.DateTime(1970, 1, 1)); 
            long timeStamp = (long)(((DateTime)value) - startTime).TotalMilliseconds; 
            writer.WriteValue(timeStamp);
        }
    }

2.配置使用时间戳转换器（到这一步API就能序列化和反序列化时间戳了）

    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            //启用标记路由功能
            config.MapHttpAttributeRoutes();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );

            //设置Datetime 到 時間戳 的互轉 
            JsonSerializerSettings jSettings = new Newtonsoft.Json.JsonSerializerSettings()
            {
                Formatting = Formatting.Indented,
                DateTimeZoneHandling = DateTimeZoneHandling.Local
            };
            jSettings.Converters.Add(new UnixDateTimeConvertor());
            config.Formatters.JsonFormatter.SerializerSettings = jSettings;

        }
    }

3.因为项目中使用了Swagger UI自动生成WebApi文档如果想接口文档Datetime显示的Example是时间戳可以如以下设置，在你自己的SwaggerConfig设置中添加Datetime及Datetime?的映射和默认值

            config
                .EnableSwagger(c =>
                    {
            //...省略无关代码

                        System.DateTime startTime = TimeZone.CurrentTimeZone.ToLocalTime(new System.DateTime(1970, 1, 1)); 
                        long exampleVal = (long)(DateTime.Now - startTime).TotalMilliseconds; 
                        Schema timeSchema = new Schema { type = "number", format = "long", example = exampleVal };

                        c.MapType<DateTime?>(() => timeSchema);
                        c.MapType<DateTime>(() => timeSchema);

                    });

最终生成的Webapi文档显示如下