c# - Automapper 表达式映射问题

Question

使用 AutoMapper.Extensions.Expression 的表达式映射未映射表达式。

这是我的模型:

public class UserDto
{
    public int Id { get; set; }
    public User User { get; set; }
    //other info
}

public class User
{
    public string Email { get; set; }
    //other info
}


public class UserEntity
{
    public int Id { get; set; }
    public string Email { get; set; }
    //other info
}

我的映射器:

public static class MapperConfiguration
{
    public static void Configure()
    {
        Mapper.Initialize(cfg =>
        {
            cfg.AddProfile(new UserDtoProfile());
        });
    }
}

internal class UserDtoProfile : Profile
{
    public UserDtoProfile()
    {
        CreateMap<UserDto, UserEntity>()
            .ForMember(dest => dest.Id, opt => opt.MapFrom(src => src.Id))
            .ForMember(dest => dest.Email, opt => opt.MapFrom(src => src.User.Email));

        CreateMap<UserEntity, UserDto>()
            .ForMember(dest => dest.Id, opt => opt.MapFrom(src => src.Id))
            .ForMember(dest => dest.User, opt => opt.MapFrom(src => Mapper.Map<UserEntity>(src)));

        CreateMap<UserEntity, User>()
           .ForMember(dest => dest.Email, opt => opt.MapFrom(src => src.Email)).ReverseMap();
    }
}

添加一个代码片段来重现该问题:

static void Main(string[] args)
{
    MapperConfiguration.Configure();
    var email = "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="85f1e0f6f1c5f1e0f6f1abe6eae8" rel="noreferrer noopener nofollow">[email protected]</a>";
    Expression<Func<UserDto, bool>> filterExpression = x => x.User.Email == email;
    var expression = Mapper.Map<Expression<Func<UserEntity, bool>>>(filterExpression);
    Console.WriteLine("Old Expression : " + filterExpression.Body);
    Console.WriteLine("New Expression : " + expression.Body);
    Console.Read();
}

其输出是:

Old Expression : (x.User.Email == "asd")
New Expression : (x.User.Email == "asd")

但是，我希望它输出:

Old Expression : (x.User.Email == "asd")
New Expression : (x.Email == "asd")

未按我预期工作的特定行是:

Expression<Func<UserDto, bool>> filterExpression = x => x.User.Email == email;
var expression = Mapper.Map<Expression<Func<UserEntity, bool>>>(filterExpression);

我正在使用 AutoMapper v8.0.0 和 AutoMapper.Extensions.Expression v2.0.0

Answer 1

您忘记配置表达式映射。您的设置应该是:

Mapper.Initialize(cfg =>
{
    cfg.AddExpressionMapping();
    cfg.AddProfile(new UserDtoProfile());
});

我还没有真正使用过AutoMapper，也从未使用过表达式映射，但是按照this github issue ，表达式的映射似乎是向后的。您当前的映射将不起作用，并且在执行时会崩溃。您需要将映射更改为:

internal class UserDtoProfile : Profile
{
    public UserDtoProfile()
    {
        CreateMap<UserDto, UserEntity>()
            .ForMember(dest => dest.Id, opt => opt.MapFrom(src => src.Id))
            .ForMember(dest => dest.Email, opt => opt.MapFrom(src => src.User.Email))
            .ReverseMap();

        CreateMap<UserEntity, User>()
           .ForMember(dest => dest.Email, opt => opt.MapFrom(src => src.Email)).ReverseMap();
    }
}

运行此命令会给出输出:

Old Expression : (x.User.Email == "asd")
New Expression : (x.Email == "asd")