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.]
Polymorphic element types in collectionsAutoMapper supports polymorphic arrays and collections, such that derived source/destination types are used if found.
AutoMapper in C# is a library used to map data from one object to another. It acts as a mapper between two objects and transforms one object type into another. It converts the input object of one type to the output object of another type until the latter type follows or maintains the conventions of AutoMapper.
By default, AutoMapper only recognizes public members. It can map to private setters, but will skip internal/private methods and properties if the entire property is private/internal.
Use AutoMapper to eliminate the need to write tedious boilerplate code when mapping objects in your application. AutoMapper is a popular object-to-object mapping library that can be used to map objects belonging to dissimilar types.
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:
Product
-> ProductViewModel
used to flatten the members of ProductCategory
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));
Using recent versions of AutoMapper, you can do something like the following:
config.CreateMap<Product, ProductViewModel>()
.ForMember(q => q.Categories, option => option.Ignore());
config.CreateMap<ProductWithCategories, ProductViewModel>()
.ConstructUsing(s => AutoMapper.Mapper.Map<ProductViewModel>(s.Product))
.ForMember(q => q.Categories, option => option.MapFrom(q => q.Categories))
.ForAllOtherMembers(o => o.Ignore();
ConstructUsing() is used to generate and populate the base class from the nested child[ren] of the source. If you have more than one such nested child, you would need to make several mapping calls to map each of them successively onto the instance generated by the first Map() call. The .ForAllOtherMembers() is relatively recent (if you don't have it, get a newer version of AutoMapper.) Unfortunately it's slightly unsafe as if you add destination members which will need mapping but forget to update the map, configuration validation will not catch it.
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