I have a record AuthResult with a class object User in it:

public record AuthResult(
    User User,
    string Token);


public class User
{
    public Guid Id { get; set; } = Guid.NewGuid();
    public string UserName { get; set; } = null!;
    public string Email { get; set; } = null!;
    public string Password { get; set; } = null!;
}

Which I want to map to a flat record AuthResponse:

public record AuthResponse(
    Guid Id,
    string UserName,
    string Email,
    string Token);

Mapping:

_mapper.Map<AuthResponse>(authResult)

Configurations I tried:

CreateMap<User, AuthResponse>();

// Gives "AuthResponse does not have a matching constructor with a parameter named 'Token'" exception
CreateMap<AuthResult, AuthResponse>()
    .ForCtorParam(ctorParamName: nameof(AuthResponse.Token), opt => opt.MapFrom(src => src.Token))
    .AfterMap((src, dest, context) => context.Mapper.Map(src.User, dest));

// Gives "AuthResponse needs to have a constructor with 0 args or only optional args."
CreateMap<AuthResult, AuthResponse>().IncludeMembers(src => src.User);

// Gives "AuthResponse needs to have a constructor with 0 args or only optional args."
CreateMap<AuthResult, AuthResponse>()
    .ConvertUsing((wrapper, destination, context) =>
        context.Mapper.Map<AuthResponse>(wrapper.User));

Am I missing something or that impossible to do with the AutoMapper?

CodePudding user response：

The other answer does work. It also requires you to change your mapping every time the record or class changes their structure/constructors.

If you want to create the map once, and never touch it again even when your entities change, I can think of two alternatives:

1. Match the properties in your record with the nested class, like so:

// Include the word 'User' to reflect the nested AuthResult.User
public record AuthResponse(
    Guid UserId, 
    string UserUserName,
    string UserEmail,
    string Token);

// This makes the mapping extremely straightforward:
cfg.CreateMap<AuthResult, AuthResponse>();

2. Or, allow your record to be created with a 0-arg constructor (respecting the error you saw)

public record AuthResponse(
    Guid Id = default,
    string UserName = default!,
    string Email = default!,
    string Token = default!);

// This allows you to use the following
cfg.CreateMap<User, AuthResponse>();
cfg.CreateMap<AuthResult, AuthResponse>()
   .IncludeMember(src => src.User);
   /* If the above doesn't work, try instead: */
   //.AfterMap((src, dest, context) => context.Mapper.Map(src.User, dest));

The 2nd option will likely be negligibly less efficient.

CodePudding user response：

I tried the following code, and it seems to work,

IConfigurationProvider configuration = new MapperConfiguration(cfg =>
            cfg.CreateMap<AuthResult, AuthResponse>()
               .ForCtorParam(ctorParamName: nameof(AuthResponse.Id), m => m.MapFrom(s => s.User.Id))
               .ForCtorParam(ctorParamName: nameof(AuthResponse.UserName), m => m.MapFrom(s => s.User.UserName))
               .ForCtorParam(ctorParamName: nameof(AuthResponse.Email), m => m.MapFrom(s => s.User.Email)));

var mapper = configuration.CreateMapper();

var result = mapper.Map<AuthResponse>(new AuthResult(new User { UserName = "Test", Email = "sas" }, "token"));