An exception of type 'AutoMapper.AutoMapperMappingException' occurred in AutoMapper.dll but was not handled in user code

Question

Somehow my code doesn\'t work any more (it did work before with the exact same code). This is the problem:

The code

I\'m trying to map some

Answer 1

It seems like there is a problem with mapping Authors property. This Aggregate call will throw an exception if the Authors sequence is null or empty.

.ForMember(x => x.Authors, 
           opt => opt.MapFrom(src => src.Book.Authors.Select(x => x.Name).Aggregate((i, j) => i + ", " + j)))