Automapper

Description

Permet le mapping d'un objet de type A vers un objet de type B.
AutoMapper utilise des convention de mapping afin de réduire le paramétrage:

• Propriétés de même nom
• Flattening
• Ignore les références null

Mapster is a faster alternative.

Liens

• Getting Started
• Static and Instance API
• AutoMapper.Collection bibliothèque externe pour géré les collections
• Map 1 object to list of objects

Setup and configuration

var config = new MapperConfiguration(cfg => { // configure mapping from Source to Dest cfg.CreateMap<Source, Dest>(); // load the configuration from AppProfile cfg.AddProfile<AppProfile>(); // load the configuration from all classes who inherits from Profile in the current assembly cfg.AddMaps(typeof(ContainerConfig).Assembly); }); IMapper mapper = config.CreateMapper(); IMapper mapper = new Mapper(config);

• Configuration

Profile

AProfile.cs

internal sealed class AProfile : Profile { public AProfile() { CreateMap<A, B>() .ForMember(dest => dest.B1, opt => opt.MapFrom(src => src.A1)); CreateMap<B, A>() .ForMember(dest => dest.A1, opt => opt.MapFrom(src => src.B1)); .ForAllOtherMembers(opt => opt.Ignore()); // ignore all other members CreateMap<A, C[]>() .ConvertUsing<AToCsConverter>(); } } public class AToCsConverter : ITypeConverter<A, C[]> { public C[] Convert(A source, C[] destination, ResolutionContext context) { return new C[]; } }

Dependency Injection

Program.cs

appBuilder.Services.AddAutoMapper(typeof(Program));

Controllers/ItemController.cs

private readonly IMapper mapper; public ItemController(IMapper mapper) { this.mapper = mapper; }

AutoMapper 12-

Add the nuget package AutoMapper.Extensions.Microsoft.DependencyInjection

Startup.cs

public void ConfigureServices(IServiceCollection services) { // if all the profiles are in the current assembly services.AddAutoMapper(typeof(Startup)); // add as parameter one type for each assembly services.AddAutoMapper(typeof(ProfileTypeFromAssembly1), typeof(ProfileTypeFromAssembly2));

Controllers/ItemController.cs

private readonly IMapper mapper; public ItemController(ItemDbContext context, IMapper mapper) { this.mapper = mapper; }

WPF

App.xaml.cs

protected override void RegisterTypes(IContainerRegistry containerRegistry) { var config = new MapperConfiguration(cfg => { cfg.AddMaps(typeof(App).Assembly); }); containerRegistry.RegisterSingleton<IMapper>(() => config.CreateMapper()); }

Exemple

var config = new MapperConfiguration(cfg => { cfg.CreateMap<A, B>() .ForMember(dst => dst.Q2, opts => opts.MapFrom(src => src.P2)); // map A.P2 → B.Q2 .ReverseMap(); // map B → A }); IMapper mapper = config.CreateMapper(); C c = new C() { P1 = 3 }; A a = new A() { P1 = 1, C1 = c }; B b = mapper.Map<B>(a); // b.P1 = 1, b.Q2 = 2, b.C1P1 = 3 class A { public int P1 { get; set; } public int P2 { get; set; } public C C1 { get; set; } } class B { public int P1 { get; set; } // mapping par convention avec A.P1 public int Q2 { get; set; } // mapping par configuration avec A.P2 public int C1P1 { get; set; } // mapping par flattening avec A.C1.P1 } class C { public int P1 { get; set; } }

• Flattening

If the mapping to a destination property has not been configured, you will get an AutoMapper.AutoMapperMappingException

Flattening

var config = new MapperConfiguration(cfg => { // default flattening // naming convention: SpecificItem.Category → SpecificItemDto.Category // flatening conventing: SpecificItem.Item.Id → SpecificItemDto.ItemId // configuration: SpecificItem.Item.Code → SpecificItemDto.Code cfg.CreateMap<SpecificItem, SpecificItemDto>() .ForMember(dest => dest.Code, opt => opt.MapFrom(src => src.Item.Code)); // flattening from composition to inheritance // naming convention: SpecificItem.Category → SpecificItemDtoV2.Category // configuration: explicitly call the mapping of Item → SpecificItemDtoV2 for the Item property cfg.CreateMap<SpecificItem, SpecificItemDtoV2>() .IncludeMembers(x => x.Item); // naming convention: Item.Id → ItemDtoV2.Id // naming convention: Item.Code → ItemDtoV2.Code cfg.CreateMap<Item, ItemDtoV2>(); // MemberList.None to skip validation and ignore unmapped destination properties like Category cfg.CreateMap<Item, SpecificItemDtoV2>(MemberList.None) .IncludeBase<Item, ItemDtoV2>(); }); config.AssertConfigurationIsValid(); IMapper mapper = config.CreateMapper(); var specificItem = new SpecificItem { Item = new Item { Id = 1, Code = 2 }, Category = 3 }; var specificItemDto = mapper.Map<SpecificItemDto>(specificItem); var specificItemDtoV2 = mapper.Map<SpecificItemDtoV2>(specificItem); // source class Item { public int Id { get; set; } public int Code { get; set; } } class SpecificItem { public int Category { get; set; } public Item Item { get; set; } } // destination class SpecificItemDto { public int ItemId { get; set; } public int Code { get; set; } public int Category { get; set; } } class ItemDtoV2 { public int Id { get; set; } public int Code { get; set; } } class SpecificItemDtoV2 : ItemDtoV2 { public int Category { get; set; } }

Unflattening

// unflattening UserDto.GroupId → User.Group.Id this.CreateMap<UserDto, User>() .ForPath(dest => dest.Group.Id, opt => opt.MapFrom(src => src.GroupId));

List and polymorphism

// avec une liste List<B> listB = Mapper.Map<List<A>, List<B>>(listA); // polymorphism cfg.CreateMap<Parent1, Parent2>() .Include<Child1, Child2>(); // IncludeAllDerived(); to include all the derived classes // without the include, the resulting list contains only Parent2 objects (no Child2 objects) cfg.CreateMap<Child1, Child2>(); var lp1 = new List<Parent1> { new Parent1 { P1 = 1}, new Child1 { P1 = 2, P2 = 22 } }; var lp2 = mapper.Map<List<Parent2>>(lp1); // Parent2, Child2 class Parent1 { public int P1 { get; set; } } class Child1 : Parent1 { public int P2 { get; set; } } class Parent2 { public int P1 { get; set; } } class Child2 : Parent2 { public int P2 { get; set; } }

• Mapping Inheritance

Pass parameter to the mapping

var config = new MapperConfiguration(cfg => { cfg.CreateMap<A, B>() .ForMember(dest => dest.P1, opt => opt.MapFrom((src, _, _, context) => src.P1 + (int)context.Items["+"])); }); IMapper mapper = config.CreateMapper(); var a = new A { P1 = 1 }; var b = mapper.Map<B>(a, opt => opt.Items["+"] = 9);

Map 1 object to multiple objects

// map 1 Group to many User class Group { public int Id { get; set; } public ICollection<int> UserIds { get; } = new List<int>(); } class User { public int Id { get; set; } public int GroupId { get; set; } }

Flatten to ValueType

var config = new MapperConfiguration(cfg => { cfg.CreateMap<(Group group, int userId), User>() .IncludeMembers(s => s.group) // call the mapping Group → User .ForMember(dest => dest.Id, opt => opt.MapFrom(src => src.userId)); cfg.CreateMap<Group, User>() .ForMember(dest => dest.GroupId, opt => opt.MapFrom(src => src.Id)) .ForMember(dest => dest.Id, opt => opt.Ignore()); }); IMapper mapper = config.CreateMapper(); var group = new Group { Id = 9, UserIds = {1, 2, 3} }; IEnumerable<(int groupId, int userId)> groupAndUserList = group.UserIds.Select(x => ValueTuple.Create(group.Id, x)); var users = mapper.Map<IEnumerable<User>>(groupAndUserList).ToList();

Flatten with a ITypeConverter

var config = new MapperConfiguration(cfg => { cfg.CreateMap<int, User>() .ForMember(dest => dest.Id, opt => opt.MapFrom(src => src)); cfg.CreateMap<Group, User>() .ForMember(dest => dest.GroupId, opt => opt.MapFrom(src => src.Id)) .ForMember(dest => dest.Id, opt => opt.Ignore()); cfg.CreateMap<Group, IEnumerable<User>>() .ConvertUsing<GroupToUsersConverter>(); }); IMapper mapper = config.CreateMapper(); var group = new Group { Id = 9, UserIds = { 1, 2, 3 } }; var users = mapper.Map<IEnumerable<User>>(group).ToList(); // use a converter to flatten a Group class GroupToUsersConverter : ITypeConverter<Group, IEnumerable<User>> { public IEnumerable<User> Convert( Group source, IEnumerable<User> destination, ResolutionContext context) { foreach (var userId in source.UserIds) { var user = context.Mapper.Map<User>(userId); context.Mapper.Map(source, user); yield return user; } } }

Conditional mapping

cfg.CreateMap<A, B>() // map A.P2 → B.Q2 if A.P2 > 0 // if A.P2 <= 0 → B.Q2 = 0 .ForMember(dest => dest.Q2, opt => { opt.Condition(src => src.P2 > 0); opt.MapFrom(src => src.P2); });

Before and After Map Action

cfg.CreateMap<A, B>() .BeforeMap((src, dest) => src.P1 += 1) .AfterMap((src, dest) => dest.P1 -= 1);

Inject a dependency during the mapping with a ValueResolver

Program.cs

// UserProvider is injected as a dependency, and AutoMapper has to be injected as a dependency too appBuilder.Services.AddScoped<IUserProvider, UserProvider>() .AddAutoMapper(typeof(AProfile));

AProfile.cs

public class AProfile : Profile { public AProfile() { this.CreateMap<A, B>() .ForMember(x => x.User, opt => opt.MapFrom<UserValueResolver>()); } } // UserProvider is retrieved as a dependency and used to resolve the mapping public class UserValueResolver(IUserProvider userProvider) : IValueResolver<A, B, User> { public User Resolve(A source, B destination, User member, ResolutionContext context) { return userProvider.GetUser(); } }

Errors

A lambda expression with a statement body cannot be converted to an expression tree

this.CreateMap<Class1, Class2>() .ForMember(dest => dest.Prop1, opt => opt.MapFrom(src => { // ... })); // use a new overload of MapFrom this.CreateMap<Class1, Class2>() .ForMember(dest => dest.Prop1, opt => opt.MapFrom((src, dest) => { // ... }));

MOQ

var mapperMock = new Mock<IMapper>(); mapperMock.Setup(x => x.Map<ItemDto>(It.IsAny<Item>())) .Returns(new ItemDto());

Unit tests

var configuration = new MapperConfiguration(cfg => cfg.AddProfile<ItemProfile>()); configuration.AssertConfigurationIsValid(); var mapper = configuration.CreateMapper(); var item = new Item { /* ... */ }; var itemDto = mapper.Map<ItemDto>(item); var mappedItem = mapper.Map<Item>(itemDto); Assert.Equal(item.Property1, mappedItem.Property1);

Mock

// create a mock mapper var mockMapper = new Mock<IMapper>(); // mock the mapping this.mockMapper.Setup(x => x.Map<MyDto>(It.IsAny<MyEntity>())) .Returns(myDto); // or create a new simplified mapper var mapper = new Mapper( new MapperConfiguration( cfg => { cfg.CreateMap<MyEntity, MyDto>() .ForMember(dest => dest.Property1, opt => opt.Ignore()); }));

Installation

NuGet → AutoMapper

ASP.NET Core

NuGet → AutoMapper.Extensions.Microsoft.DependencyInjection

Startup.cs

public void ConfigureServices(IServiceCollection services) { services.AddAutoMapper(typeof(Startup));

MyController.cs

private readonly IMapper mapper; public MyController(IMapper mapper) { this.mapper = mapper; B b = this.mapper.Map<A, B>(a);

Configuration dans Profile