Use automapper to update destination object and set nullable type property value to null

Question

It seems that nullable type properties in source is ignored and not copied to destination.

Consider these classes:

public class Source 
{
    public int? Test { get; set; }
}

public class Destination 
{
    public int? Test { get; set; }
}

Mapping:

Mapper.CreateMap<Source, Destination>();

var source = new Source() { Test = 1 };
var destination = new Destination();

Mapper.Map<Source, Destination>(source, destination);

Assert.AreEqual(source.Test, destination.Test); //true

source.Test = null;

Mapper.Map<Source, Destination>(source, destination);

Assert.AreEqual(source.Test, destination.Test); //false (null, 1)

It worked when I used:

Mapper.CreateMap<Source, Destination>()
    .ForMember(m => m.Test, o => o.ResolveUsing(m => m.Test));

But I don't want to set that per property, can you set that globally? Or is there any other way to achieve this?

Answer 1

Seems that creating maps for each nullable type to itself like:

Mapper.CreateMap<int?, int?>()
    .ConvertUsing(v => v);

Seems to work as a fix. But I would rather have a complete solution with all nullable types then specifiyng them one by one. Easy to miss something.