C#•2y ago

✅ ef core can't translate a query

query:

var username = "some username";
var user = await _db.Users
            .FirstOrDefaultAsync(u => u.Username.Value == username);

var username = "some username";
var user = await _db.Users
            .FirstOrDefaultAsync(u => u.Username.Value == username);

UserConfiguration:

public void Configure(EntityTypeBuilder<UserEntity> builder)
    {
        builder.HasKey(u => u.Id);
        
        builder.Property(u => u.Username)
            .HasConversion(
                u => u.Value, 
                value => new Username(value));

        builder.Property(u => u.Password)
            .HasConversion(
                p => p.Value,
                value => Password.FromValue(value));
    }

public void Configure(EntityTypeBuilder<UserEntity> builder)
    {
        builder.HasKey(u => u.Id);
        
        builder.Property(u => u.Username)
            .HasConversion(
                u => u.Value, 
                value => new Username(value));

        builder.Property(u => u.Password)
            .HasConversion(
                p => p.Value,
                value => Password.FromValue(value));
    }

Password VO:

public class Password
{
    public string Value { get; private set; }
    private readonly IPasswordHasher _passwordHasher;

    private Password(string value)
    {
        Value = value;
        _passwordHasher = null!;
    }
    
    private Password(string value, IPasswordHasher passwordHasher)
    {
        _passwordHasher = passwordHasher;
        Value = value;
    }

    public static Password Create(string value, IPasswordHasher passwordHasher)
    {
        Validate(value);

        return new(passwordHasher.GetHash(value), passwordHasher);
    }

    public static Password FromValue(string value)
    {
        return new Password(value);
    }

    public void Update(string newValue)
    {
        Validate(newValue);

        Value = _passwordHasher.GetHash(newValue);
    }
    
    private static void Validate(string value)
    {
        if (value.Length is not (<= 100 and >= 8))
            throw new Exceptions.InvalidPasswordLengthException();
    }
}

public class Password
{
    public string Value { get; private set; }
    private readonly IPasswordHasher _passwordHasher;

    private Password(string value)
    {
        Value = value;
        _passwordHasher = null!;
    }
    
    private Password(string value, IPasswordHasher passwordHasher)
    {
        _passwordHasher = passwordHasher;
        Value = value;
    }

    public static Password Create(string value, IPasswordHasher passwordHasher)
    {
        Validate(value);

        return new(passwordHasher.GetHash(value), passwordHasher);
    }

    public static Password FromValue(string value)
    {
        return new Password(value);
    }

    public void Update(string newValue)
    {
        Validate(newValue);

        Value = _passwordHasher.GetHash(newValue);
    }
    
    private static void Validate(string value)
    {
        if (value.Length is not (<= 100 and >= 8))
            throw new Exceptions.InvalidPasswordLengthException();
    }
}

10 Replies

demndevOP•2y ago

and the UserEntity:

public class UserEntity : EntityBase
{
    public Username Username { get; }
    public Password Password { get; } // TODO: work with password hashing
    private List<NoteEntity> _notes = new();
    public IEnumerable<NoteEntity> Notes => _notes.AsReadOnly();
    
    public UserEntity(Password password, Username username)
    {
        Password = password;
        Username = username;
    }

    public bool Authenticate(Username username, Password password)
    {
        return Username.Value == username.Value && Password.Value == password.Value;
    }

public class UserEntity : EntityBase
{
    public Username Username { get; }
    public Password Password { get; } // TODO: work with password hashing
    private List<NoteEntity> _notes = new();
    public IEnumerable<NoteEntity> Notes => _notes.AsReadOnly();
    
    public UserEntity(Password password, Username username)
    {
        Password = password;
        Username = username;
    }

    public bool Authenticate(Username username, Password password)
    {
        return Username.Value == username.Value && Password.Value == password.Value;
    }

what am i doing wrong? exception:

The LINQ expression 'DbSet<UserEntity>()
    .Where(u => u.Username.Value == __username_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'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

The LINQ expression 'DbSet<UserEntity>()
    .Where(u => u.Username.Value == __username_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'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

i also tried using .HasColumnName, but it didn't help

JakenVeina•2y ago

why in the world is Username its own class? or struct? u.Username.Value is invalid Username is not an entity type you've registered with EF, so it doesn't know how to navigate .Value and the value conversion you've defined doesn't help all that does is tell EF to store that column as a string, and how to convert the two back and forth as yhey go to and from the database

jcotton42•2y ago

smells of DDD

    private List<NoteEntity> _notes = new();
    public IEnumerable<NoteEntity> Notes => _notes.AsReadOnly();

    private List<NoteEntity> _notes = new();
    public IEnumerable<NoteEntity> Notes => _notes.AsReadOnly();

what's up with this? @demndev you're trying to be wayyyyyy too clever with your entities some cleverness is fine, like in my Discord bots I have a value converter for Snowflake that converts it to/from ulong but generally your database entities should just be data no cleverness

demndevOP•2y ago

it's a value object yes, it's something like DDD

jcotton42•2y ago

you can set up a value converter but then you need to use Username opaquely i.e. just do someUsername == anotherUsername not someUsername.Value == anotherUsername.Value

demndevOP•2y ago

okay… what is a value converter and how can i set up it?

jcotton42•2y ago

it's the HasConversion stuff you're already doing so if the drop the .Value stuff, it should all work

demndevOP•2y ago

thanks!

jcotton42•2y ago

remember, EF isn't actually running the expressions you give it it's translating them to SQL so it's looking for a column to act on and your Username column doesn't have a Value property in the database

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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✅ ef core can't translate a query