HotChocolate get value of not queried field

I'm using HotChocolate 13. Here is my model FArticle (the field ArRef is my id):

public partial class FArticle
{
    public string ArRef { get; set; } = null!;

    public string? SomeValue { get; set; }

    public static void ConfigureModelBuilder(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<FArticle>(entity =>
        {
            entity.HasIndex(e => e.ArRef, "UKA_F_ARTICLE_AR_Ref").IsUnique();
            entity.Property(e => e.SomeValue)
                .HasMaxLength(69)
                .IsUnicode(false)
                .HasColumnName("SomeValue");
            entity.Property(e => e.ArRef)
                .HasMaxLength(19)
                .IsUnicode(false)
                .HasColumnName("AR_Ref");
        });
    }
}

My Query:

public class Query
{
    [UseFArticleMapping]
    [UseOffsetPaging(MaxPageSize = 100, IncludeTotalCount = true, DefaultPageSize = 20)]
    [UseProjection]
    [UseFiltering]
    [UseSorting]
    public IEnumerable<FArticle> GetFArticles([Service] DbContext context) =>
        context.FArticles;
}

As you can see I added my own middleware UseFArticleMapping.

Now when I launch the query:

{
    fArticles(
        skip: 0
        take: 1
    ) {
        items {
            someValue
        }
    }
}

I can access my list of FArticle with my middleware UseFArticleMapping:

public class UseFArticleMappingAttribute : ObjectFieldDescriptorAttribute
{
    public UseFArticleMappingAttribute([CallerLineNumber] int order = 0)
    {
        Order = order;
    }

    protected override void OnConfigure(
        IDescriptorContext context,
        IObjectFieldDescriptor descriptor,
        MemberInfo member
    )
    {
        descriptor.Use(next => async middlewareContext =>
        {
            await next(middlewareContext);
            object? result = middlewareContext.Result;
            // https://stackoverflow.com/a/68459545/6824121
            if (result is CollectionSegment<FArticle> fArticles)
            {
                foreach (var fArticle in fArticles.Items)
                {
                    fArticle.ArRef // fArticle.ArRef is null
                }
            }
        });
    }
}

But as I didn't specify the arRef in the query (only someValue) fArticle.ArRef returns null.

How can I tell HotChocolate to load ArRef without adding arRef in my query so I can access it in my middleware ?

You need to use IsProjected

public partial class FArticle
{
    [IsProjected(true)]
    public string ArRef { get; set; } = null!;
}