AutoMapper is a convention-based object-oriented mapper that transforms a source object into a destination object.
- If both source and destination objects have the same properties with the same types, then AutoMapper can perform with almost zero configuration
- With complex/dissimilar objects, you can still use automapper's built-in type converters, transformers and resolvers to perform the mapping
-
Create a new folder named AspNetCoreAutoMapperDemo and go to that directory
mkdir AspNetCoreAutoMapperDemo cd AspNetCoreAutoMapperDemo -
Create a new solution named AspNetCoreAutoMapperDemo
dotnet new sln -n AspNetCoreAutoMapperDemo -
Add a new project into the solutin
dotnet new mvc -f net6.0 -n AspNetCoreAutoMapperDemo -
Add the project to the solution
dotnet sln add AspNetCoreAutoMapperDemo/AspNetCoreAutoMapperDemo.csproj -
Open the project in vscode
code . -
Now add the required packages for automapper
dotnet add package AutoMapper -v 12.0.1 dotnet add package AutoMapper.Extensions.Microsoft.DependencyInjection -v 12.0.1 -
Configure AutoMapper into services
builder.Services.AddAutoMapper(Assembly.GetExecutingAssembly()); -
Create two classes that can be used for mapping. One for source object and the other for destination object
dotnet new class -n Employee dotnet new class -n EmployeeModelpublic class Employee { public int Id { get; set; } public string Title { get; set; } public string Name { get; set; } public int? Age { get; set; } public DateTime? RegistrationDate { get; set; } }public class EmployeeModel { public int Id { get; set; } public string Title { get; set; } public string Name { get; set; } public int? Age { get; set; } public DateTime? RegistrationDate { get; set; } } -
Now we will create AutoMapper Mapping Profiles. While doing the mapping from one type to another, AutoMapper looks for mapping profiles. Mapping profiles gives AutoMapper all information and configuration related to mappings. To create a mapping profile, we need to create a class that derives from the Profile class available in AutoMapper library
dotnet new class -n MappingProfilepublic class MappingProfile : Profile { public MappingProfile() { CreateMap<Employee, EmployeeModel>(); } } -
AutoMapper has a service called IMapper that can be injected into any component or service to map objects from one type to another. Lets create IEmployeeService interface and EmployeeService class and inject IMapper service in the constructor.
mkdir Services cd services dotnet new interface -n IEmployeeService dotnet new class -n EmployeeServicepublic interface IEmployeeService { List<EmployeeModel> GetEmployees(); }public class EmployeeService : IEmployeeService { private readonly IMapper _mapper; public EmployeeService(IMapper mapper) { _mapper = mapper; } public List<EmployeeModel> GetEmployees() { var employees = new List<Employee>() { new Employee() { Id = 1, Title = "Mr", Name = "Simon", Age = 32, RegistrationDate = new DateTime(2015, 12, 5) }, new Employee() { Id = 2, Name = "David", Age = 35, RegistrationDate = new DateTime(2013, 3, 15) }, new Employee() { Id = 3, Title = "Mr", Name = "Peter", Age = 29 } }; return _mapper.Map<List<EmployeeModel>>(employees); } } -
Inject the IEmployeeService implementation into the services
builder.Services.AddScoped<IEmployeeService, EmployeeService>(); -
Inject the IEmployeeService into HomeController and return the List from the Index action method to the rezor view
public class HomeController : Controller { private readonly ILogger<HomeController> _logger; private readonly IEmployeeService _employeeService; public HomeController(ILogger<HomeController> logger, IEmployeeService employeeService) { _logger = logger; _employeeService = employeeService; } public IActionResult Index() { return View(_employeeService.GetEmployees()); } } -
Update the Index.cshtml razor view to represent the List and run the application to see the list we are updating.
@model IEnumerable<EmployeeModel> @{ ViewData["Title"] = "Index"; Layout = "~/Views/Shared/_Layout.cshtml"; } <div class="row"> <div class="col"> <h1>Employees</h1> </div> </div> <br /> <table class="table"> <thead> <tr> <th>@Html.DisplayNameFor(model => model.Id)</th> <th>@Html.DisplayNameFor(model => model.Title)</th> <th>@Html.DisplayNameFor(model => model.Name)</th> <th>@Html.DisplayNameFor(model => model.Age)</th> <th>@Html.DisplayNameFor(model => model.RegistrationDate)</th> </tr> </thead> <tbody> @foreach (var item in Model) { <tr> <td>@Html.DisplayFor(modelItem => item.Id)</td> <td>@Html.DisplayFor(modelItem => item.Title)</td> <td>@Html.DisplayFor(modelItem => item.Name)</td> <td>@Html.DisplayFor(modelItem => item.Age)</td> <td>@Html.DisplayFor(modelItem => item.RegistrationDate)</td> </tr> } </tbody> </table> -
For large projects, there could be hundreds of objects to map, and adding the CreateMap statement for every single mapping seems quite a non-productive and time-consuming task. We can avoid this type of mapping configurations using a C# interface and some reflection. The interface has a single method called Mapping and it has a default implementation that simply calls the same CreateMap method. Now create an interface IMapFrom
dotnet new interface -n IMapFrompublic interface IMapFrom<T> { void Mapping(Profile profile) => profile.CreateMap(typeof(T), GetType()); } -
Now update the EmployeeModel class to implement IMapFrom interface. This tells AutoMapper that we want to map the EmployeeModel with the Employee class
public class EmployeeModel : IMapFrom<Employee> { public int Id { get; set; } public string Title { get; set; } public string Name { get; set; } public int? Age { get; set; } public DateTime? RegistrationDate { get; set; } } -
This makes the configuratin a lot simple. We can implement IMapFrom interface on any class we want to map with the T class and AutoMapper will do the rest. Once we have all those classes ready to map, we do not want to register them all manually. So let's add some automation in our MappingProfile class we created earlier.
public class MappingProfile : Profile { /*public MappingProfile() { CreateMap<Employee, EmployeeModel>(); }*/ public MappingProfile() { ApplyMappingsFromAssembly(Assembly.GetExecutingAssembly()); } private void ApplyMappingsFromAssembly(Assembly assembly) { var types = assembly.GetExportedTypes() .Where(t => t.GetInterfaces().Any(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IMapFrom<>))) .ToList(); foreach (var type in types) { var instance = Activator.CreateInstance(type); var methodInfo = type.GetMethod("Mapping") ?? type.GetInterface("IMapFrom`1").GetMethod("Mapping"); methodInfo?.Invoke(instance, new object[] { this }); } } }We are using the .NET Reflection framework to scan the assembly and looking for all classes that are implementing the IMapFrom interface. Once we have all those types available, we are simply invoking their Mapping method. Now run the project and check out the Index page is working or not with this configuration update. 17. To define custom mappings, you need to implement the Mapping method available in the IMapFrom interface we created above. Suppose we do not want to map the RegistrationDate Property of the Employee class, we can use ForMember method that allows us to customize individual members of the class. We need to specify the property we want to customize and then we can call the ignore method. The ignore method skips the mapping of the current property
public class EmployeeModel : IMapFrom<Employee> { public int Id { get; set; } public string Title { get; set; } public string Name { get; set; } public int? Age { get; set; } public DateTime? RegistrationDate { get; set; } public void Mapping(Profile profile) { var c = profile.CreateMap<Employee, EmployeeModel>().ForMember(d => d.RegistrationDate, opt => opt.Ignore()); } }Run the project and we will notice that the data of RegistrationDate property is not mapped from Employee object to EmployeeModel object
-
The title property of employee David is not specified and this is why Title property column is empty for David. We can tell AutoMapper to replace the null value with any custom value.
public class EmployeeModel : IMapFrom<Employee> { public int Id { get; set; } public string Title { get; set; } public string Name { get; set; } public int? Age { get; set; } public DateTime? RegistrationDate { get; set; } public void Mapping(Profile profile) { var c = profile.CreateMap<Employee, EmployeeModel>() .ForMember(d => d.RegistrationDate, opt => opt.Ignore()) .ForMember(d => d.Title, opt => opt.NullSubstitute("N/A")); } }Now run the project and see that the null value for Title is replaced with N/A.
-
We can also map dissimilar objects using the AutoMapper MapFrom method. Lets add a new property OfficeAddress in the Employee class and another new property WorkAddress in EmployeeModel class. Update the Employee, EmployeeModel, EmployeeService, Index as following-
public class Employee { public int Id { get; set; } public string Title { get; set; } public string Name { get; set; } public int? Age { get; set; } public DateTime? RegistrationDate { get; set; } public string OfficeAddress { get; set; } }public class EmployeeModel : IMapFrom<Employee> { public int Id { get; set; } public string Title { get; set; } public string Name { get; set; } public int? Age { get; set; } public DateTime? RegistrationDate { get; set; } public string WorkAddress { get; set; } public void Mapping(Profile profile) { var c = profile.CreateMap<Employee, EmployeeModel>() .ForMember(d => d.RegistrationDate, opt => opt.Ignore()) .ForMember(d => d.Title, opt => opt.NullSubstitute("N/A")) .ForMember(d => d.WorkAddress, opt => opt.MapFrom(s => s.OfficeAddress)); } }public class EmployeeService : IEmployeeService { private readonly IMapper _mapper; public EmployeeService(IMapper mapper) { _mapper = mapper; } public List<EmployeeModel> GetEmployees() { var employees = new List<Employee>() { new Employee() { Id = 1, Title = "Mr", Name = "Simon", Age = 32, RegistrationDate = new DateTime(2015, 12, 5) }, new Employee() { Id = 2, Name = "David", Age = 35, RegistrationDate = new DateTime(2013, 3, 15), OfficeAddress = "123 ABC Street" }, new Employee() { Id = 3, Title = "Mr", Name = "Peter", Age = 29 } }; return _mapper.Map<List<EmployeeModel>>(employees); } }@model IEnumerable<EmployeeModel> @{ ViewData["Title"] = "Index"; Layout = "~/Views/Shared/_Layout.cshtml"; } <div class="row"> <div class="col"> <h1>Employees</h1> </div> </div> <br /> <table class="table"> <thead> <tr> <th>@Html.DisplayNameFor(model => model.Id)</th> <th>@Html.DisplayNameFor(model => model.Title)</th> <th>@Html.DisplayNameFor(model => model.Name)</th> <th>@Html.DisplayNameFor(model => model.Age)</th> <th>@Html.DisplayNameFor(model => model.RegistrationDate)</th> <th>@Html.DisplayNameFor(model => model.WorkAddress)</th> </tr> </thead> <tbody> @foreach (var item in Model) { <tr> <td>@Html.DisplayFor(modelItem => item.Id)</td> <td>@Html.DisplayFor(modelItem => item.Title)</td> <td>@Html.DisplayFor(modelItem => item.Name)</td> <td>@Html.DisplayFor(modelItem => item.Age)</td> <td>@Html.DisplayFor(modelItem => item.RegistrationDate)</td> <td>@Html.DisplayFor(modelItem => item.WorkAddress)</td> </tr> } </tbody> </table>Now run the project and see the update for WorkAddress property.