Automapper to do datetime conversions

automapper_timezone_sample.cs

/******

An example to automatically perform datetime conversions using automapper
Assumptions:
* all inputs are in client Local time (MyInputModel)
* all datetimes are stored as UTC (MyDto)
* all datetimes retrieved from storage are in UTC and contain the destination timezone (MyDto)
* if destination not supplied, use the server local time zone

*******/

using System;
using AutoMapper;


namespace UtcConverter
{
    class MyDto
    {
        public DateTime CreateDate;
        public string TimeZone;
    }

    class MyOutputModel
    {
        public DateTime CreateDate;
        public string TimeZone;
    }

    class MyInputModel
    {
        public DateTime CreateDate;
    }

    class DtoToOutputMapper
    {
        public static IMapper Mapper { get; private set; }

        static DtoToOutputMapper()
        {
            RegisterMappings();
        }
        
        public static void RegisterMappings()
        {
            var config = new MapperConfiguration(cfg =>
            {
                cfg.CreateMap<DateTime, DateTime>().ConvertUsing<UtcToLocalConverter>();
            });
            Mapper = config.CreateMapper();
        }
    }

    class InputToDtoMapper
    {
        public static IMapper Mapper { get; private set; }

        static InputToDtoMapper()
        {
            RegisterMappings();
        }

        public static void RegisterMappings()
        {
            var config = new MapperConfiguration(cfg =>
            {
                cfg.CreateMap<DateTime, DateTime>().ConvertUsing<LocalToUtcConverter>();
                cfg.CreateMap<MyInputModel, MyDto>().ForMember("TimeZone", opt => opt.Ignore());
            });
            Mapper = config.CreateMapper();
        }
    }

    class UtcToLocalConverter : ITypeConverter<DateTime, DateTime>
    {
        public DateTime Convert(DateTime source, DateTime destination, ResolutionContext context)
        {
            var inputDate = source;
            if (inputDate.Kind == DateTimeKind.Utc)
            {
                var timeZoneId = context.Items.ContainsKey("tz") 
                    ? context.Items["tz"].ToString() 
                    : TimeZoneInfo.Local.Id;
                var localizedDate = TimeZoneInfo.ConvertTime(
                    inputDate, 
                    TimeZoneInfo.Utc, 
                    TimeZoneInfo.FindSystemTimeZoneById(timeZoneId));
                return localizedDate;
            }
            return inputDate;
        }
    }

    class LocalToUtcConverter : ITypeConverter<DateTime, DateTime>
    {
        public DateTime Convert(DateTime source, DateTime destination, ResolutionContext context)
        {
            var inputDate = source;
            if (inputDate.Kind != DateTimeKind.Utc)
            {
                return inputDate.ToUniversalTime();
            }
            return inputDate;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            MyInputModel myInput = new MyInputModel
            {
                CreateDate = new DateTime(2019, 6, 1, 3, 0, 0, 0, DateTimeKind.Local)
            };
            MyDto dto = new MyDto();
            MyOutputModel myOutput = new MyOutputModel();

            InputToDtoMapper.Mapper.Map(myInput, dto);
            dto.TimeZone = "Mountain Standard Time";
            DtoToOutputMapper.Mapper.Map(dto, myOutput, opt => opt.Items["tz"] = dto.TimeZone);

            Console.WriteLine($"input.createdDate = {myInput.CreateDate} ({myInput.CreateDate.Kind})");
            Console.WriteLine($"dto.createDate = {dto.CreateDate} (UTC)");
            Console.WriteLine($"output.createdDate = {myOutput.CreateDate} ({dto.TimeZone})");

            Console.ReadKey();
        }
    }
}