Set up Automapper in ASP.NET Core

Add the main AutoMapper Package to your solution via NuGet.

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

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>();
     }
 }

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();

}

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!
    }
}

References
https://stackoverflow.com/questions/40275195/how-to-set-up-automapper-in-asp-net-core

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