AutoMapper ForMember method breaks the functionality of mapping

Question

I want to use AutoMapper in my .Net 6 APIs to convert the entity model User to DTO model UserDTO.
The User model class is:

public class User : BaseEntity
{
  public Guid Id { get; set; }
  public string FirstName { get; set; } = null!;
  public string LastName { get; set; } = null!;
  public string Avatar { get; set; } = null!;
  public string Email { get; set; } = null!;
  public ICollection<Book>? FavoriteBooks { get; set; }
}

And the UserDTO is a record as follows:

public record UserDTO(Guid Id, string FullName, string Avatar, string Email);

I have added the required package AutoMapper.Extensions.Microsoft.DependencyInjection v.12.0.0, and the configuration steps are given below:
1- Create MappingProfile that inherits from the Profile class

public class MappingProfiles : Profile
{
  public MappingProfiles()
  {
    CreateMap<User, UserDTO>()
      .ForMember(
          dest => dest.FullName,
          opt => opt.MapFrom(src => string.Join(" ", src.FirstName, src.LastName))
      );
  }
}

2- Register the service in Program.cs file:

builder.Services.AddAutoMapper(typeof(Program));

3- Use the mapper as an injected service inside Service project:

public IEnumerable<UserDTO> GetAllUsers(bool trackChanges)
{
   var users = _repository.User.GetAllUsers(trackChanges);
   return _mapper.Map<IEnumerable<UserDTO>>(users);
}

When I call the GetAllUsers method in postman, I get the following error:

Error mapping types.
Mapping types:
List -> IEnumerable

After a few days of struggling and searching, I realized that the .ForMember() method breaks the functionality of the profile class. In other words, if I change the UserDTO record:

public record UserDTO(Guid Id, string FirsName, string Avatar, string Email);

the FullName filed changed to FirstName to have compatibility with the User model. Also change the MappingProfile class:

public class MappingProfiles : Profile
{
  public MappingProfiles()
  {
    CreateMap<User, UserDTO>();
  }
}

the GetAllUsers method works as expected. So to conclude, if I add the .ForMember() method to the constructor of the MappingProfile class as in documentation, it breaks the functionality of the CreatMap method.

How should I use the .ForMember() method to map the User model to the corresponding DTO? Is this method obsolete? Is there any replacement for this method?

Answer 1

I found 2 solutions:

Solution 1:
I created a method to get the full name of the user. The method name should be prefixed with get:

The naming convention can cover simpler examples where the source object has a property, method, or method with a “Get” as a prefix with the same name as the property of a destination object.

so I have modified the User model class and added the following method:

public class User : BaseEntity
{
    ... // User model properties
    public string GetFullName() => $"{this.FirstName} {this.LastName}";
}

and removed the .ForMemeber()` method from the profile class:

public MappingProfiles()
{
    CreateMap<User, UserDTO>();
}

Solution 2:
It seems that .ForMember() is obsolete, I have found an alternative for that, .ForCtorParam():

public MappingProfiles()
{
    CreateMap<User, UserDTO>()
      .ForCtorParam(
          "FullName",
          opt => opt.MapFrom(src => string.Join(" ", src.FirstName, src.LastName))
      );
}

In these ways, I have converted my User model class to UserDTO.