Automapper 表达式映射问题

Question

Expression mapping using AutoMapper.Extensions.Expression is not mapping the expression.

Here are my models:

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
}

My mappers:

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();
    }
}

Add a snippet to reproduce the issue:

static void Main(string[] args)
{
    MapperConfiguration.Configure();
    var email = "test@test.com";
    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();
}

The output of this is:

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

However, I'm expecting it to output:

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

The particular lines that aren't working as I expect are:

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

I'm using AutoMapper v8.0.0 and AutoMapper.Extensions.Expression v2.0.0

Answer 1

You forgot to configure the Expression mapping. Your setup should be:

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

I haven't really used AutoMapper, and have never used the expression mapping, but as per this github issue , the mapping appears to be backwards for expressions. Your current mapping won't work, and will crash when executing. You'll need to change the mapping to be:

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();
    }
}

Running this gives the output:

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