I’ve been trying for quite some time to get this code to work. But it just doesn’t, I don’t understand why:

public async Task<PaginatedData<DbUser>> GetPaginatedAsync(
    int pageSize,
    int page,
    UserTypes userType,
    string fullName
)
{
    var countFacet = AggregateFacet.Create(
        "count",
        PipelineDefinition<DbUser, AggregateCountResult>.Create(
            new[] { PipelineStageDefinitionBuilder.Count<DbUser>() }
        )
    );

    var dataFacet = AggregateFacet.Create(
        "data",
        PipelineDefinition<DbUser, DbUser>.Create(
            new[]
            {
                PipelineStageDefinitionBuilder.Sort(Builders<DbUser>.Sort.Ascending(x => x.Id)),
                PipelineStageDefinitionBuilder.Skip<DbUser>((page - 1) * pageSize),
                PipelineStageDefinitionBuilder.Limit<DbUser>(pageSize),
                PipelineStageDefinitionBuilder.Project<DbUser, DbUser>(
                    Builders<DbUser>.Projection.Exclude("password")
                ),
            }
        )
    );

    var filter =
        userType == UserTypes.All
            ? Builders<DbUser>.Filter.Empty
            : Builders<DbUser>.Filter.Eq(x => x.UserType, (int)userType);
    filter &= Builders<DbUser>.Filter.Eq(x => x.IsDeleted, false);

    if (!string.IsNullOrWhiteSpace(fullName))
    {
        var regexPattern = new BsonRegularExpression($"^{fullName}", "i");
        filter &= Builders<DbUser>.Filter.Regex("full_name", regexPattern);
    }

    var aggregation = await databaseContext
        .Users.Aggregate()
        .Match(filter)
        .Facet(countFacet, dataFacet)
        .ToListAsync();

    var count =
        aggregation
            .First()
            .Facets.First(x => x.Name == "count")
            .Output<AggregateCountResult>()
            ?.FirstOrDefault()
            ?.Count ?? 0;

    var totalPages = Math.Ceiling(count / (double)pageSize);

    var data = aggregation.First().Facets.First(x => x.Name == "data").Output<DbUser>();

    var employeeData = data.Select(x => x);

    return new PaginatedData<DbUser>
    {
        CurrentPage = page,
        PageSize = pageSize,
        TotalPages = (int)totalPages,
        TotalRecords = count,
        Data = employeeData
    };
}

The amount of records is always returning as 0.

I have tried applying a Match stage at the dataFacet, and that also doesn’t work.

This is another method that does the same regex filtering:

public async Task<IEnumerable<DbUser>> SearchAheadUserAsync(UserTypes userType, string fullName)
{
    var regexPattern = new BsonRegularExpression($"^{fullName}", "i");
    var filter = Builders<DbUser>.Filter.Regex("full_name", regexPattern);

    filter &=
        userType == UserTypes.All
            ? Builders<DbUser>.Filter.Empty
            : Builders<DbUser>.Filter.Eq(x => x.UserType, (int)userType);

    var results = await databaseContext.Users.Find(filter).ToListAsync();

    return results;
}

And it works correctly, so the issue lies at the usage of facets.