EF Core 7: The LINQ expression 'DbSet could not be translated when using Value Object

[pantonis]

EF COre The LINQ expression 'DbSet could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'.

I have the following Name ValueObject:

 public class Name : ValueObject
 {
     public string Value { get; private set; }

     protected Name()
     {
     }

     private Name(string value)
     {
         Value = value;
     }

     public static Result<Name> Create(string name)
     {
         name = (name ?? string.Empty).Trim();

         if (string.IsNullOrEmpty(name))
             return Result.Failure<Name>("Name should not be empty");

         if (name.Length > 128)
             return Result.Failure<Name>("Name is too long");

         return Result.Success(new Name(name));
     }

     protected override IEnumerable<IComparable> GetEqualityComponents()
     {
         yield return Value;
     }
 }

and the following table

public class Team
{
    public int Id { get; private set; }
    public Name Name { get; private set; }
}

and in my dbcontext

 modelBuilder.Entity<Team>(x =>
 {
     x.Property(p => p.Name)
         .IsRequired()
         .HasConversion(p => p.Value, p => Name.Create(p).Value)
         .HasMaxLength(128);
 }

When I try to run the following

 var teamQuery = await (from team in dbContext.Team.AsNoTracking()
                        where team.Name.Value.Contains(input.SearchText)
                        select new 
                        {
                            Id = team.Id,
                            Name = team.Name.Value,
                        }).ToListAsync();

I get the following error:

 - The LINQ expression 'DbSet<Team>()
    .Where(t => t.Name.Value.Contains(__input_SearchText_0))' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync

[Vladimir Khorikov]

It most likely doesn't like the Name.Value part.

LINQ queries don't work well, both in EF and NH, so you'd need to come up with some workaround, unfortunately.

[Pavel Zemlianikin]

It is working with the ComplexProperty mapping feature from EF Core 8.

var hostBuilder = Host.CreateEmptyApplicationBuilder(new() { Args = args });

hostBuilder.Logging.AddConsole().SetMinimumLevel(LogLevel.Debug);

hostBuilder.Services.AddDbContext<SampleDbContext>(b =>  b.UseNpgsql(connectionString);

var host = hostBuilder.Build();

var sampleDbContext = host.Services.GetRequiredService<SampleDbContext>();

var teams = sampleDbContext.Set<Team>();

teams.AddRange(new Team {Name = new("some1")}, new Team {Name = new("anothersome")}, new Team {Name = new("newone")});

sampleDbContext.SaveChanges();

var teamDtos = await teams.AsNoTracking().Where(x => x.Name.Value.Contains("some"))
    .Select(x => new {x.Id, Name = x.Name.ToString()}).ToListAsync();

host.Services.GetRequiredService<ILogger<DbContext>>()
    .LogDebug("Fetched teams: {@Teams}", teamDtos);

public class SampleDbContext(DbContextOptions options) : DbContext(options) {
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) { }

    protected override void OnModelCreating(ModelBuilder b) {
        b.UseIdentityByDefaultColumns();

        b.Entity<Team>(static e => {
            e.ToTable("teams");

            e.HasKey(x => x.Id)
                .HasName("teams_pk");

            e.Property(x => x.Id).HasColumnName("id");

            // This one            
            var name = e.ComplexProperty(x => x.Name).IsRequired();
            name.Property(x => x.Value).HasColumnName("name").IsRequired();
        });
    }
}

public class Team {
    public long Id { get; init; }

    public required Name Name { get; init; } 
}

public class Name(string value) : SimpleValueObject<string>(value);