ASP .NET REST API

Data Transfer Objects (DTOs)

A DTO is an object that defines how the data will be sent and recieved over the network (usually as JSON). Without a DTO the JSON response (or reqest) could contain irrilevant, wrong or unformatted data. Moreover, by decoupling the JSON response from the actual data model, it's possible to change the latter without breaking the API. DTOs must be mapped to the internal methods.

In EntityDTO.cs:

namespace <Namespace>.DTOs
{
    // define the data to be serialized in JSON (differs from model)
    public class EntityDTO
    {
        // only properties to be serialized
    }
}

DTO mapping with Automapper

Required NuGet Packages:

AutoMapper
AutoMapper.Extensions.Microsoft.DependencyInjection

A good way to organize mapping configurations is with profiles.

In EntitiesProfile.cs:

using AutoMapper;
using <Namespace>.DTOs;
using <Namespace>.Model;

namespace <Namespace>.Profiles
{
    public class EntitiesProfile : Profile
    {
        public EntitiesProfile()
        {
            CreateMap<Entity, EntityDTO>();  // map entity to it's DTO
        }
    }
}

Controller (No View)

Uses Dependency Injection to recieve a suitable implementation of IEntityRepo,

Service Lifetimes

AddSingleton: same for every request
AddScoped: created once per client
Transient: new instance created every time

In Startup.cs:

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers();
    services.AddScoped<IEntityRepo, EntityRepo>();  // map the interface to its implementation, needed for dependency injection
}

Request Mappings

using <App>.Model;
using <App>.Repo;
using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;

namespace <App>.Controllers
{
    [Route("api/endpoint")]
    [ApiController]
    public class EntitiesController : ControllerBase  // MVC controller w/o view
    {
        // service or repo (DAL) injection
        
        private readonly IMapper _mapper;  // AutoMapper class

        [HttpGet]  // GET api/endpoint
        public ActionResult<EntityDTO> SelectAllEntities()
        {
            ...

            return Ok(_mapper.Map<EntityDTO>(entity));
        }
    }
}

Simple API Controller

[Route("api/endpoint")]
[ApiController]
public class EntitiesController : ControllerBase
{
    // service or repo (DAL) injection

    [HttpGet]
    public ActionResult<TEntity> SelectAll()
    {
        ...
        return Ok(entity);
    }
}

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