Prevent Automapper creating object property with null values

Question

I'm using Automapper with EF Core. EF entities:

public class Team
{
    public Guid? Id { get; set; }

    public string Name { get; set; }

    public Guid? OrganizationId { get; set; }

    public Organization Organization { get; set; }
}

public class Organization
{
    public Guid Id { get; set; }

    public string Name { get; set; }

    public ICollection<Team> Teams { get; set; }
}

And corresponding DTOs:

public class TeamDto
{
    public Guid? Id { get; set; }

    public string Name { get; set; }

    public OrganizationDto Organization { get; set; }
}

public class OrganizationDto
{
    public Guid? Id { get; set; }

    public string Name { get; set; }
}

Type mappings:

cfg.CreateMap<Organization, OrganizationDto>();

cfg.CreateMap<TeamDto, Team>()
    .ForMember(teamEntity => teamEntity.Organization, opt => opt.Ignore())
    .ForMember(teamEntity => teamEntity.OrganizationId, opt => opt.MapFrom(
        orgDto => orgDto == null ? null : orgDto.Id))
    .ReverseMap();

When I try to map from Team entity -> dto, when Organization is null on Team entity, TeamDto has non null Organization property with null values. e.g.

var team = new Team
{
    Name = "New Team"
};

// team.Organization is null as well as team.OrganizationId
var teamDto = s_mapper.Map<TeamDto>(team);

This is not desirable, as I want TeamDto's Organization property to be null. I tried to configure this mapping via ForMember but it didn't take effect:

cfg.CreateMap<TeamDto, Team>()
    .ForMember(teamEntity => teamEntity.Organization, opt => opt.Ignore())
    .ForMember(teamEntity => teamEntity.OrganizationId, opt => opt.MapFrom(
        orgDto => orgDto == null ? null : orgDto.Id))
    .ReverseMap()
    .ForMember(teamDto => teamDto.Organization, opt => opt.MapFrom(
        teamEntity => teamEntity.Organization == null ? null : new OrganizationDto
    {
        Id = teamEntity.Organization.Id,
        Name = teamEntity.Organization.Name
    }));

How can I configure this to have Organization property be set to null when source is also null.

One way I can achieve this is by using AfterMap, but I'm looking for a solution that can be applied to all such cases without specifying AfterMap for each case.

AutoMapper v. 9.0.0

Lucian Bargaoanu · Accepted Answer · 2021-01-14 12:01:34Z

5

Sometimes ReverseMap just gets in the way, as it seems to be the case here. You can always avoid it and simply create the reverse map explicitly.

answered Jan 14, 2021 at 12:01

Lucian Bargaoanu

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Comments

Marcilio Oliveira · Accepted Answer · 2022-07-08 16:13:44Z

0

You can use the Null Substitution funcionallity into the ForMember..

https://docs.automapper.org/en/stable/Null-substitution.html

In my case, when try to load a null entity using ITyperConverter, the NullSubstitue comes in on the ForMember just like this, other wise de ReverseMap creates a instance with null values.

return mapping.ForMember(property, opt => { 
                opt.NullSubstitute(null);
                opt.MapFrom(mapFrom);
            });

answered Jul 8, 2022 at 16:13

Marcilio Oliveira

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