Is there a way to tell AutoMapper to ignore all of the properties except the ones which are mapped explicitly?
I have external DTO classes which are likely to change from the outside and I want to avoid specifying each property to be ignored explicitly, since adding new properties will break the functionality (cause exceptions) when trying to map them into my own objects.
From what I understood the question was that there are fields on the destination which doesn't have a mapped field in the source, which is why you are looking for ways to Ignore those non mapped destination fields.
Instead of implementing and using these extension method you could simply use
Mapper.CreateMap<sourceModel, destinationModel>(MemberList.Source);
Now the automapper knows that it needs to only validate that all the source fields are mapped but not the other way around.
You can also use:
Mapper.CreateMap<sourceModel, destinationModel>(MemberList.Destination);