Mapping child type as parent, with explicit casting, maps derived properties

[Xriuk]

Source/destination types

public class Entity{
  public string MyId { get; set; }
  
  public string MyString { get; set; }
}


public class DtoEntityBase{
  public string MyString { get; set; }
}

public class DtoEntityDerived : DtoEntityBase {
  public string MyId { get; set; }
}

Mapping configuration

c.CreateMap<DtoEntityBase, Entity>()
  .ForMember(e => e.MyId, c => c.Ignore());
c.CreateMap<DtoEntityDerived, Entity>();

DtoEntityDerived a = new DtoEntityDerived{
  MyId = "AAA",
  MyString = "BBB"
};
Entity e = mapper.Map<DtoEntityBase, Entity>(a);
Console.WriteLine(e.MyId + " " + e.MyString);

Version: 12.0.1

Expected behavior

Should print " BBB" as the MyId property should not be mapped

Actual behavior

Prints "AAA BBB" as MyId property is being mapped despite the map types being DtoEntityBase to Entity

Steps to reproduce

Fiddle

It seems that the passed types are ignored and actual types of the passed variables are used, is this by design?

[lbargaoanu]

I think this is better suited for StackOverflow.