using AutoMapper;
using AutoMapper.Attributes;
using System.Reflection;

namespace ConsoleApp2
{
    class MapsFromSourceAttribute : MapsFromAttribute
    {
        public MapsFromSourceAttribute() : base(typeof(Source)) { }

        public void ConfigureMapping(IMappingExpression<Source, Destination> mappingExpression)
        {
            mappingExpression.ForMember(T => T.BarValue, T => T.MapFrom(W => W.FooValue));
        }
    }

    class MapsFromSourceExAttribute : MapsFromAttribute
    {
        public MapsFromSourceExAttribute() : base(typeof(Source)) { }

        public void ConfigureMapping(IMappingExpression<Source, DestinationEx> mappingExpression)
        {
            // This >>GETS<< called, but the result is like it doesn't at all!

            mappingExpression.ForMember(T => T.BarValue, T => T.MapFrom(W => W.FooValue)); // This property is here again since this is independent mapping.
            mappingExpression.ForMember(T => T.FooBarValue, T => T.MapFrom(W => -W.FooValue)); // New property, but both don't get mapped.
        }
    }

    class Source
    {
        public string Property { get; set; }
        public int FooValue { get; set; }
    }

    [MapsFromSource] // If this attribute is removed, than the issue is RESOLVED. But we don't want to remove it, they're supposed to work independently.
    class Destination
    {
        public string Property { get; set; }
        public int BarValue { get; set; }
    }

    [MapsFromSourceEx]
    class DestinationEx : Destination
    {
        public int FooBarValue { get; set; }
    }

    class Program
    {
        static Program()
        {
            Mapper.Initialize(c =>
            {
                // Manual mapping here is overridden and the issue persists.

                Assembly.GetExecutingAssembly().MapTypes(c);

                // Manual mapping here SOLVES the issue, and the properties are mapped successfully.
            });
        }

        static void Main(string[] args)
        {
            Source s = new Source()
            {
                Property = "stringProp",
                FooValue = 1
            };

            // d's properties BarValue and FooBarValue are not mapped!
            DestinationEx d = Mapper.Map<DestinationEx>(s);
        }
    }
}