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

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

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.

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);

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EF Core 7: The LINQ expression 'DbSet could not be translated when using Value Object #518

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EF Core 7: The LINQ expression 'DbSet could not be translated when using Value Object #518

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vkhorikov commented on Sep 27, 2023

PNZeml commented on Nov 24, 2023

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