好了，接下来直接上代码来说明。

EntityModels.Employee.cs

public class Employee
{
    public Guid Id { get; set; }
    public Guid CompanyId { get; set; }

    public string EmployeeNo { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public Gender Gender { get; set; }
    public DateTime DateOfBirth { get; set; }

    public Company Company { get; set; }
}

Models.EmployeeDto.cs

public class EmployeeDto
{
    public Guid Id { get; set; }
    public Guid CompanyId { get; set; }

    public string EmployeeNo { get; set; }
    public string Name { get; set; }
    public string GenderDisplay { get; set; }
    public int Age { get; set; }
}

我们可以观察到, 两个实体之间有很多不同的地方, 比如名字拆分啊, 出生日期和年龄啊等等, 我之前的做法就是硬生生手写代码转换, 但是经过学习大佬们的代码, 发现了一个类库, 在此算是记录一下吧

AutoMapper.Extensions.Microsoft.DependencyInjection

可以通过NuGet安装，使用的时候也非常简单, 建立Profile文件夹, 新建一个EmployeeProfile类, 继承于Profile。

public class EmployeeProfile: Profile
{
    public EmployeeProfile()
    {
        CreateMap()
            .ForMember(dest => dest.Name,
                opt => opt.MapFrom(src => $"{src.FirstName} {src.LastName}"))
            .ForMember(dest => dest.GenderDisplay,
                opt => opt.MapFrom(src => src.Gender.ToString()))
            .ForMember(dest => dest.Age,
                opt => opt.MapFrom(src => DateTime.Now.Year - src.DateOfBirth.Year));
    }
}

在使用的时候只需要这样, 注入mapper, 然后就是很简单的操作了, 简直了, 功能非常强大!!!

[ApiController]
[Route("api/companies/{companyId}/employees")]
public class EmployeesController: ControllerBase
{
    private readonly IMapper _mapper;
    private readonly ICompanyRepository _companyRepository;

    public EmployeesController(IMapper mapper, ICompanyRepository companyRepository)
    {
        _mapper = mapper ?? throw new ArgumentNullException(nameof(mapper));
        _companyRepository = companyRepository ?? throw new 
            ArgumentNullException(nameof(companyRepository));
    }
    [HttpPost]
    public async Task>
        CreateEmployeeForCompany(Guid companyId, EmployeeAddDto employee)
    {
        if (!await _companyRepository.CompanyExistsAsync(companyId))
        {
            return NotFound();
        }

        var entity = _mapper.Map(employee);

        _companyRepository.AddEmployee(companyId, entity);
        await _companyRepository.SaveAsync();

        var dtoToReturn = _mapper.Map(entity);

        return CreatedAtRoute(nameof(GetEmployeeForCompany), new
        {
            companyId = companyId,
            employeeId = dtoToReturn.Id
        }, dtoToReturn);
    }
}

本文原创地址：https://www.linuxprobe.com/netcore-dto-automapper.html编辑：薛鹏旭，审核员：逄增宝