Getting list of Ids from collection throws Unable to cast object of type 'LiteDB.ObjectId' to type 'System.String'

[ssteiner]

Version
LiteDb 5.0.21 on Win11 2023H2 on .NET 8.0.7

Describe the bug

Here's my object model:

public class PhoneBookCategory
{
    public string Id { get; set; }

    public string Name { get; set; }
}

Then I populate my DB as follows:

PhoneBookCategory category1 = new()
{
    Id = ObjectId.NewObjectId().ToString(),
    Name = "Category1"
};
PhoneBookCategory category2 = new()
{
    Id = ObjectId.NewObjectId().ToString(),
    Name = "Category2"
};
PhoneBookCategory category3 = new()
{
    Id = ObjectId.NewObjectId().ToString(),
    Name = "special Subcategory3"
};

database.GetCollection<PhoneBookCategory>().Insert(category1);
database.GetCollection<PhoneBookCategory>().Insert(category2);
database.GetCollection<PhoneBookCategory>().Insert(category3);

And I'm trying to fetch the list of Ids

var accessibleObjects = database.GetCollection().Query().Select(x => x.Id).ToList();

When I run this, it throws

Unable to cast object of type 'LiteDB.ObjectId' to type 'System.String'. at at LiteDB.LiteQueryable1.<ToEnumerable>b__27_1(BsonValue x) at System.Linq.Enumerable.SelectEnumerableIterator2.ToList()
at LiteDB.LiteQueryable1.ToList() at LiteDbTest.LiteDbContext.<>c__DisplayClass21_01.b__0(LiteDatabaseContext context)
at LiteDbTest.LiteDbContext.PerformDatabaseOperation[T](Func`2 myFunc, IUserInformation userInfo, String methodName)

What I would expect is to get a List containing all Ids in my database.

If I remove the ToList(), it runs fine. If I replace ToList() with .FirstOrDefault(), it runs fine.

[Vernizze]

Hi! I have a same problem in a same environment configuration of ssteiner, but not in cast to string but to long.

My stack trace:

Unable to cast object of type 'LiteDB.ObjectId' to type 'System.Int64'.- at lambda_method168(Closure, Object, Object) at LiteDB.BsonMapper.DeserializeObject(EntityMapper entity, Object obj, BsonDocument value) at LiteDB.BsonMapper.Deserialize(Type type, BsonValue value) at LiteDB.LiteQueryable 1.<ToEnumerable>b__27_2(BsonDocument x) at System.Linq.Enumerable.SelectEnumerableIterator 2.MoveNext() at System.Linq.Enumerable.<Any>g__WithEnumerator|36_0[TSource](IEnumerable 1 source) at System.Linq.Enumerable.Any[TSource](IEnumerable 1 source)

[ssteiner]

@Vernizze : did you ever look in the database directly? I had the lingering feeling that in my case, I had a messed up value in the database. And since the IEnumerable only gets evaluated when I access the data, that would explain why it threw on ToList()

As I was using exclusive DB access mode, I never looked at the data.

[Joy-less]

I run this code in the upstream repository and it works fine:

using Xunit;

namespace LiteDB.Tests.Issues;

public class Issue2527_Tests
{
    [Fact]
    public void Test() 
    {
        using LiteDatabase database = new(new ConnectionString()
        {
            Filename = "Demo.db",
        });

        PhoneBookCategory category1 = new()
        {
            Id = ObjectId.NewObjectId().ToString(),
            Name = "Category1"
        };
        PhoneBookCategory category2 = new()
        {
            Id = ObjectId.NewObjectId().ToString(),
            Name = "Category2"
        };
        PhoneBookCategory category3 = new()
        {
            Id = ObjectId.NewObjectId().ToString(),
            Name = "special Subcategory3"
        };

        database.GetCollection<PhoneBookCategory>().Insert(category1);
        database.GetCollection<PhoneBookCategory>().Insert(category2);
        database.GetCollection<PhoneBookCategory>().Insert(category3);

        var accessibleObjects = database.GetCollection<PhoneBookCategory>().Query().Select(x => x.Id).ToList();
    }

    public class PhoneBookCategory
    {
        public string Id { get; set; }
        public string Name { get; set; }
    }
}

Changing string to long also works. Maybe your database IDs are corrupted or the issue got fixed. Please send more info if you still have the issue @ssteiner @Vernizze.

[ssteiner]

I wasn't able to create a repro sample that you could run - as I said in my previous post, I suspect I had some data corruption somewhere.