AutoMapper - Trying to flatten my object property to string but getting an error

Question

I am trying to map my ProductDto to Product class. I get an error when mapping the string property in ProductDto class to a Brand property in the Product class.

AutoMapper.AutoMapperMappingException: Error mapping types.

Mapping types:
ProductDto -> Product
SilksyAPI.Dto.ProductDto -> SilksyAPI.Entities.Product

Type Map configuration:
ProductDto -> Product
SilksyAPI.Dto.ProductDto -> SilksyAPI.Entities.Product

Destination Member:
Brand

 ---> AutoMapper.AutoMapperMappingException: Missing type map configuration or unsupported mapping.

Mapping types:
String -> Brand
System.String -> SilksyAPI.Entities.Brand

Here is my mapping profile:

CreateMap<Product, ProductDto>()
    .ForMember(dest => dest.Brand, opt => opt.MapFrom(p => p.Brand.Name))
    .ForMember(dest => dest.Categories, opt => opt.MapFrom(p => p.ProductCategories.Select(pc => pc.Category.Name)));

CreateMap<ProductDto, Product>()
    .ForMember(dest => dest.Brand, opt => opt.MapFrom(src => src.Name));

Classes:

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public decimal Price { get; set; }

    public int BrandId { get; set; }
    public Brand Brand { get; set; }

    public ICollection<ProductCategory> ProductCategories { get; set; }
}

public class Brand
{
    public int Id { get; set; }

    [Required]
    [MaxLength(100)]
    public string Name { get; set; }
}

Dto Class

 public class ProductDto
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public decimal Price { get; set; }
    public string Brand { get; set; }
    public List<string> Categories { get; set; }

}

I have tried different mapping profiles but I cannot map from ProductDto to Product but can map from Product to ProductDto with no problem.

Here are a few other things I tried

CreateMap<Brand, string>()
    .IncludeMembers(b => b.Name);


CreateMap<Product, ProductDto>()
    .ForMember(dest => dest.Brand, opt => opt.MapFrom(p => p.Brand.Name))
    .ForMember(dest => dest.Categories, opt => opt.MapFrom(p => p.ProductCategories.Select(pc => pc.Category.Name)))
    .ReverseMap();

And

Mapper.CreateMap<Brand, string>().ConvertUsing(source => source.Name ?? string.Empty);

https://docs.automapper.org/en/stable/Flattening.html

Answer 1

From your first mapping profile, when mapping from ProductDto to Product, for Brand property, you need to create a new Brand instance as below:

cfg.CreateMap<ProductDto, Product>()
   .ForMember(dest => dest.Brand, opt => opt.MapFrom(src => new Brand { Name = src.Name }));

Sample Program

---

For .IncludeMembers()

I don't think it suits your scenario as you are mapping from object to string but not object to object.

---

For .ConvertUsing()

You need to add the code below to mapping from string to Brand for Brand property.

cfg.CreateMap<string, Brand>()
   .ConvertUsing(source => new Brand { Name = source });

Sample program (.ConvertUsing())