C# – How to set up Automapper in ASP.NET Core

asp.net-coreautomapperc++

I'm relatively new at .NET, and I decided to tackle .NET Core instead of learning the "old ways". I found a detailed article about setting up AutoMapper for .NET Core here, but is there a more simple walkthrough for a newbie?

Best Solution

I figured it out! Here's the details:

  1. Add the main AutoMapper Package to your solution via NuGet.

  2. Add the AutoMapper Dependency Injection Package to your solution via NuGet.

  3. Create a new class for a mapping profile. (I made a class in the main solution directory called MappingProfile.cs and add the following code.) I'll use a User and UserDto object as an example.

     public class MappingProfile : Profile {
         public MappingProfile() {
             // Add as many of these lines as you need to map your objects
             CreateMap<User, UserDto>();
             CreateMap<UserDto, User>();
         }
     }
    
  4. Then add the AutoMapperConfiguration in the Startup.cs as shown below:

     public void ConfigureServices(IServiceCollection services) {
         // .... Ignore code before this
    
        // Auto Mapper Configurations
         var mapperConfig = new MapperConfiguration(mc =>
         {
             mc.AddProfile(new MappingProfile());
         });
    
         IMapper mapper = mapperConfig.CreateMapper();
         services.AddSingleton(mapper);
    
         services.AddMvc();
    
     }
    
  5. To invoke the mapped object in code, do something like the following:

     public class UserController : Controller {
    
         // Create a field to store the mapper object
         private readonly IMapper _mapper;
    
         // Assign the object in the constructor for dependency injection
         public UserController(IMapper mapper) {
             _mapper = mapper;
         }
    
         public async Task<IActionResult> Edit(string id) {
    
             // Instantiate source object
             // (Get it from the database or whatever your code calls for)
             var user = await _context.Users
                 .SingleOrDefaultAsync(u => u.Id == id);
    
             // Instantiate the mapped data transfer object
             // using the mapper you stored in the private field.
             // The type of the source object is the first type argument
             // and the type of the destination is the second.
             // Pass the source object you just instantiated above
             // as the argument to the _mapper.Map<>() method.
             var model = _mapper.Map<UserDto>(user);
    
             // .... Do whatever you want after that!
         }
     }