C# AutoMaper简单使用

AutoMapper它是一种对象与对象之间的映射器，让AutoMapper有意思的就是在于它提供了一些将类型A映射到类型B这种无聊的实例，只要B遵循AutoMapper已经建立的惯例，那么大多数情况下就可以进行相互映射了。

安装
nuget搜索AutoMapper.Extensions.Microsoft.DependencyInjection 安装，会自动安装AutoMapper

创建Entities文件夹，新建User Model

namespace Blogs.WebApi.Entities
{
    public class Users
    {
        public int ID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string Email { get; set; }
        public string Gender { get; set; }
    }
}

创建Dto文件夹，新建UsersDto类，为了掩饰，把FistName和LastName合并为FullName

namespace Blogs.WebApi.Dto
{
    public class UsersDto
    {
        public int ID { get; set; }
        public string FullName { get; set; }
        public string Email { get; set; }
        public string Gender { get; set; }
    }
}

Startup.cs类增加数据库服务

services.AddDbContext<DataContext>(options =>
                options.UseSqlServer(Configuration.GetConnectionString("Default")));

新建DataContext类,DbContext包含所有的实体映射到数据库表的实体集(DbSet < TEntity >)

using Microsoft.EntityFrameworkCore;

namespace Blogs.WebApi.Entities
{
    public class DataContext : DbContext
    {
        public DataContext(DbContextOptions<DataContext> options) : base(options)
        {

        }
        public DbSet<Users> Users { get; set; }
    }
}

创建Services文件夹，新建IUsersRepository仓储接口

using System.Collections.Generic;
using System.Threading.Tasks;
using Blogs.WebApi.Entities;

namespace Blogs.WebApi.Services
{
    public interface IUsersRepository
    {
        Task<IEnumerable<Users>> GetAllUsers();  //获取所有用户
        Task<Users> GetUsersByID(int id);        //根据ID查询单个用户
    }
}

新建UsersRepository实现IUsersRepository仓储接口

using System.Collections.Generic;
using System.Threading.Tasks;
using Blogs.WebApi.Entities;
using Microsoft.EntityFrameworkCore;

namespace Blogs.WebApi.Services
{
    public class UsersRepository : IUsersRepository
    {
        private readonly DataContext _dataContext;

        public UsersRepository(DataContext dataContext)
        {
            _dataContext = dataContext;
        }
        public async Task<IEnumerable<Users>> GetAllUsers()
        {
            return await _dataContext.Users.AsNoTracking().ToListAsync();
        }

        public async Task<Users> GetUsersByID(int id)
        {
            return await _dataContext.Users.AsNoTracking().FirstOrDefaultAsync(u => u.ID == id);
        }
    }
}

Startup.cs类注入服务依赖

//每次请求，都获取一个新的实例。同一个请求获取多次会得到相同的实例
services.AddScoped<IUsersRepository, UsersRepository>();
//获取已加载到此应用程序域的执行上下文中的程序集。详情AppDomain.GetAssemblies 方法
services.AddAutoMapper(AppDomain.CurrentDomain.GetAssemblies());

新建Profiles文件夹创建UserProfile类创建映射，继承自Profile类映射集合

using AutoMapper;
using Blogs.WebApi.Dto;
using Blogs.WebApi.Entities;

namespace Blogs.WebApi.Profiles
{
    public class UserProfile : Profile
    {
        public UserProfile()
        {
            CreateMap<Users, UsersDto>()
                .ForMember(
                    dest => dest.FullName, opt =>
                    {
                        opt.MapFrom(s => s.FirstName + "." + s.LastName);
                    });
        }
    }
}

从Controller文件夹创建UsersController控制器

using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using AutoMapper;
using Blogs.WebApi.Dto;
using Blogs.WebApi.Services;
using Microsoft.AspNetCore.Mvc;

namespace Blogs.WebApi.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class UsersController : ControllerBase
    {
        private readonly IUsersRepository _usersRepository;
        private readonly IMapper _mapper;

        public UsersController(IUsersRepository usersRepository, IMapper mapper)
        {
            _usersRepository = usersRepository;
            _mapper = mapper;
        }
        // GET: api/<UsersController>
        [HttpGet]
        public async Task<ActionResult<IEnumerable<UsersDto>>> Get()
        {
            var users = await _usersRepository.GetAllUsers();
            return _mapper.Map<IEnumerable<UsersDto>>(users).ToList();
        }

        // GET api/<UsersController>/5
        [HttpGet("{id}")]
        public async Task<ActionResult<UsersDto>> Get(int id)
        {
            var user = await _usersRepository.GetUsersByID(id);
            return _mapper.Map<UsersDto>(user);
        }
    }
}

PostMan效果展示

入门讲解推荐视频https://www.bilibili.com/video/BV1XJ411q7yy?p=12