c# - How to use AutoMapper to map destination object with a child object in the source object?

Question

I have the source and destination objects like this:

class ProductWithCategories // Source class
{
    public Product Product { get; set; } // Product is an EF entity class
    public IEnumerable<Category> Categories { get; set; }
}

class ProductViewModel // Dest class
{
    public int Id { get; set; }
    // Other properties with the same name as Product class

    public IEnumerable<CategoryViewModel> Categories { get; set; }
}

So, my need is to map the values of source.Product into dest, and then source.Categories into dest.Categories. Is it possible with AutoMapper?

I have tried this and I was not surprised when it failed:

        config.CreateMap<ProductWithCategories, ProductViewModel>()
            .ForMember(q => q, option => option.MapFrom(q => q.Product))
            .ForMember(q => q.Categories, option => option.MapFrom(q => q.Categories));

Here is the exception I received:

[AutoMapperConfigurationException: Custom configuration for members is only supported for top-level individual members on a type.]

Answer 1

After some discussion with OP, it turns out his main need is to quickly map a child/nested object inside the source object to the flattened destination object. He does not want to write a mapping for every property of the destination.

Here is a way to achieve this:

• Define a mapping Product -> ProductViewModel used to flatten the members of Product
• Define a mapping Category to CategoryViewModel

• Define a mapping ProductWithCategories -> ProductViewModel that maps the categories, and then in the aftermap, map the Product:

  config.CreateMap<ProductWithCategories, ProductViewModel>() .ForMember(q => q.Id, option => option.Ignore()) // flattened in AfterMap .ForMember(q => q.Categories, option => option.MapFrom(q => q.Categories)) .AfterMap((src, dst) => Mapper.Map(src.Product, dst));