DTOs and Object Mapping (AutoMapper)

Mind Map Summary

• Topic: DTOs and Object Mapping
• Core Concepts:
  • Data Transfer Object (DTO): An object that is used to transfer data between different layers of an application, such as between the service layer and the presentation layer.
  • Object Mapping: The process of converting an object from one type to another.
  • AutoMapper: A popular object mapping library for .NET.
• Benefits of DTOs:
  • Decoupling: Decouple your internal domain models from your external API contracts.
  • Security: Prevent over-posting and under-posting attacks.
  • Performance: Reduce the amount of data that is sent over the wire.
• Pros and Cons of AutoMapper:
  • Pros: Reduces boilerplate code, easy to use, convention-based.
  • Cons: Can be slow if not configured correctly, can hide complexity.

Practice Exercise

Create an EF Core entity Product and a corresponding ProductDto. Configure AutoMapper to map between the two. In a controller, use the mapping to transform the entity to a DTO before returning it to the client, and to map an incoming DTO to an entity for saving to the database.

Answer

1. Entity and DTO:

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

public class ProductDto
{
    public int Id { get; set; }
    public string Name { get; set; }
}

2. AutoMapper Profile:

using AutoMapper;

public class MappingProfile : Profile
{
    public MappingProfile()
    {
        CreateMap<Product, ProductDto>();
        CreateMap<ProductDto, Product>();
    }
}

3. Controller:

using AutoMapper;
using Microsoft.AspNetCore.Mvc;

[ApiController]
[Route("[controller]")]
public class ProductsController : ControllerBase
{
    private readonly MyDbContext _context;
    private readonly IMapper _mapper;

    public ProductsController(MyDbContext context, IMapper mapper)
    {
        _context = context;
        _mapper = mapper;
    }

    [HttpGet("{id}")]
    public async Task<IActionResult> Get(int id)
    {
        var product = await _context.Products.FindAsync(id);
        var productDto = _mapper.Map<ProductDto>(product);
        return Ok(productDto);
    }

    [HttpPost]
    public async Task<IActionResult> Post(ProductDto productDto)
    {
        var product = _mapper.Map<Product>(productDto);
        _context.Products.Add(product);
        await _context.SaveChangesAsync();
        return CreatedAtAction(nameof(Get), new { id = product.Id }, product);
    }
}