C#•3y ago

✅ Combining a List inside of a Select

I have an object:

    public class BackendSuccess
    {
        [Key]
        public int id { get; set; }
        public DateTime creationDate { get; set; }
        public ICollection<Label> labels { get; set; } = new List<Label>(); // BEEEEG list of base64 encoded labels
    }

    public class BackendSuccess
    {
        [Key]
        public int id { get; set; }
        public DateTime creationDate { get; set; }
        public ICollection<Label> labels { get; set; } = new List<Label>(); // BEEEEG list of base64 encoded labels
    }

    public class BackendSuccess
    {
        [Key]
        public int id { get; set; }
        public DateTime creationDate { get; set; }
        public ICollection<Label> labels { get; set; } = new List<Label>(); // BEEEEG list of base64 encoded labels
    }

    public class BackendSuccess
    {
        [Key]
        public int id { get; set; }
        public DateTime creationDate { get; set; }
        public ICollection<Label> labels { get; set; } = new List<Label>(); // BEEEEG list of base64 encoded labels
    }

And when i want to grab them all from the database, I want them combined by

creationDate

creationDate

creationDate

creationDate using LINQ.

For example:

creationDate:2023-12-15, labels:[{1},{2}]

creationDate:2023-12-15, labels:[{1},{2}]

creationDate:2023-12-15, labels:[{1},{2}]

creationDate:2023-12-15, labels:[{1},{2}] and

creationDate:2023-12-15, labels:[{3},{4}]

creationDate:2023-12-15, labels:[{3},{4}]

creationDate:2023-12-15, labels:[{3},{4}]

creationDate:2023-12-15, labels:[{3},{4}]
would combine to create

creationDate:2023-12-15, labels:[{1},{2},{3},{4}]

creationDate:2023-12-15, labels:[{1},{2},{3},{4}]

creationDate:2023-12-15, labels:[{1},{2},{3},{4}]

creationDate:2023-12-15, labels:[{1},{2},{3},{4}]
The order of the elements in

labels

labels

labels

labels doesn't matter, I just want them combined.

Angius•12/15/23, 11:18 PM

var stuff = await _context.Labels
    .GroupBy(l => l.BackendSuccess.CreationDate)
    .Select(g => new ThingDto {
        CreationDate = g.Key,
        Labels = g.Select(l => l.Id)
    })
    .ToListasync();

var stuff = await _context.Labels
    .GroupBy(l => l.BackendSuccess.CreationDate)
    .Select(g => new ThingDto {
        CreationDate = g.Key,
        Labels = g.Select(l => l.Id)
    })
    .ToListasync();

Angius•12/15/23, 11:18 PM

Something like that?

UntoldTitanOP•12/15/23, 11:20 PM

Lemme try that

UntoldTitanOP•12/15/23, 11:29 PM

I put that in, im just converting the DateTimeDateTime to a DateOnly so that they'll actually match lol

UntoldTitanOP•12/15/23, 11:50 PM

made some changes, this is what I have now @ZZZZZZZZZZZZZZZZZZZZZZZZZ,

            return await _context.Successes
                .GroupBy(l => l.creationDate)
                .Select(p => new BackendSuccess { creationDate = p.Key, labels = (ICollection<Label>)p.Select(l => l.labels) })
                .ToListAsync();

            return await _context.Successes
                .GroupBy(l => l.creationDate)
                .Select(p => new BackendSuccess { creationDate = p.Key, labels = (ICollection<Label>)p.Select(l => l.labels) })
                .ToListAsync();

(ICollection<Label>)p.Select(l => l.labels)(ICollection<Label>)p.Select(l => l.labels) seems to be an ICollection<ICollection<>> tho, why would that be?

Angius•12/15/23, 11:51 PM

Because each success has a collection of labels, and each group will be a collection of those collections

Angius•12/15/23, 11:51 PM

That's why I went through label and not success

Angius•12/15/23, 11:51 PM

You can use .SelectMany().SelectMany() instead of .Select().Select() there

Angius•12/15/23, 11:52 PM

That'll flatten it

AAngius You can use `.SelectMany()` instead of `.Select()` there

UntoldTitanOP•12/15/23, 11:55 PM

ohhh, i didnt notice that XD

AAngius You can use `.SelectMany()` instead of `.Select()` there

UntoldTitanOP•12/15/23, 11:56 PM

ok, ty

UntoldTitanOP•12/15/23, 11:57 PM

it works!! thank you so much!