如何在不使用 AutoMapper 的情况下手动映射 DTO？

我正在学习 C#.NET Core 并尝试在不使用 AutoMapper 的情况下创建 DTO 映射，因为我正在独自开发一个小项目，并且想在使用额外的包之前了解基础知识，令人惊讶的是我无法在 stackoverflow.com 上轻松找到答案，或者我可能会使用错误的关键字搜索。

顺便说一句，下面是我的代码，我在 GetEmployee 方法下成功映射到 EmployeeForShortDto 。不幸的是，我不知道如何将它映射到 GetAllEmployee 下，只是因为返回数据是一个集合，而不是单个记录。请指教。

EmployeeController.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using NetCoreWebApplication1.Dto;
using NetCoreWebApplication1.Repository;
using NetCoreWebApplication1.Other;

namespace NetCoreWebApplication1.Controller
{
    [Route("api/[controller]")]
    [ApiController]
    public class EmployeeController : ControllerBase
    {
        private readonly IMasterRepository _repo;

        public EmployeeController(IMasterRepository repo)
        {
            _repo = repo;
        }

        [HttpGet("{id}")]
        public async Task<IActionResult> GetEmployee(int id)
        {
            var data = await _repo.GetEmployee(id);
            if (data == null) return NotFound();
            var dataDto = new EmployeeForShortDto()
            {
                Id = data.Id,
                EmpCode = data.EmpCode,
                Fname = data.Fname,
                Lname = data.Lname,
                Age = NetCoreWebApplication1.Other.Extension.CalcAge(data.DateBirth)
            };

            return Ok(dataDto);
        }

        [HttpGet]
        public async Task<IActionResult> GetAllEmployee()
        {
            var data = await _repo.GetAllEmployee();
            return Ok(data);
        }

    }
}

MasterRepository.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using NetCoreWebApplication1.Models;

namespace NetCoreWebApplication1.Repository
{
    public class MasterRepository : IMasterRepository
    {
        private readonly PrDbContext _context;

        public MasterRepository(PrDbContext context)
        {
            _context = context;
        }


        // Employee
        public async Task<List<Employee>> GetAllEmployee()
        {
            var data = await _context.Employee.ToListAsync();
            return data;
        }

        public async Task<Employee> GetEmployee(int id)
        {
            var data = await _context.Employee.FirstOrDefaultAsync(x => x.Id == id);
            return data;
        }

        // Generic methods
        public void Add<T>(T entity) where T : class
        {
            _context.Add(entity);
        }

        public void Delete<T>(T entity) where T : class
        {
            _context.Remove(entity);
        }

        public async Task<bool> SaveAll()
        {
            return await _context.SaveChangesAsync() > 0;
        }
    }
}

您可以使用扩展方法从实体类型映射到 DTO 类型。

public static EmployeeForShortDto ToDto(this Employee employee)
{
    if (employee != null)
    {
        return new EmployeeForShortDto
        {
            Id = employee.Id,
            EmpCode = employee.EmpCode,
            Fname = employee.Fname,
            Lname = employee.Lname,
            Age = NetCoreWebApplication1.Other.Extension.CalcAge(employee.DateBirth)
        };
    }

    return null;
}

然后在需要的地方使用。

[HttpGet("{id}")]
public async Task<IActionResult> GetEmployee(int id)
{
    var data = await _repo.GetEmployee(id);

    if (data == null) 
    {
        return NotFound();
    }

    return Ok(data.ToDto());
}

[HttpGet]
public async Task<IActionResult> GetAllEmployee()
{
    var data = await _repo.GetAllEmployee();

    return Ok(data.Select(x => x.ToDto()));
}