IQueryableExtensionsForPaginatedResults.cs

public sealed class PaginatedResults<T>
{
    public required IReadOnlyList<T> Results { get; init; }
    public required int Page { get; init; }
    public required int PageSize { get; init; }
    public required int TotalCount { get; init; }

    public int TotalPages => (int)Math.Ceiling(TotalCount / (double)PageSize);
}

// this code assumes you want 1-indexed page numbers (instead of 0-indexed).
// if you prefer 0-indexed, remove the "- 1" and "+ 1"s below.

public static class IQueryableExtensionsForPaginatedResults
{
    public static PaginatedResults<T> ToPaginatedResults<T>(this IQueryable<T> query, int pageNumber, int pageSize)
    {
        var totalNumberOfRecords = query.Count();

        pageNumber = Math.Clamp(pageNumber - 1, 0, (int)Math.Ceiling(totalNumberOfRecords / (float)pageSize));
        
        var results = query
            .Skip(pageNumber * pageSize)
            .Take(pageSize)
            .ToList();

        return new PaginatedResults<T>()
        {
            Results = results,
            Page = pageNumber + 1,
            PageSize = pageSize,
            TotalCount = totalNumberOfRecords
        };
    }

    public static async Task<PaginatedResults<T>> ToPaginatedResultsAsync<T>(this IQueryable<T> query, int pageNumber, int pageSize, CancellationToken cancellationToken)
    {
        var totalNumberOfRecords = await query.CountAsync(cancellationToken);
        
        pageNumber = Math.Clamp(pageNumber - 1, 0, (int)Math.Ceiling(totalNumberOfRecords / (float)pageSize));

        var results = await query
            .Skip(pageNumber * pageSize)
            .Take(pageSize)
            .ToArrayAsync(cancellationToken);

        return new PaginatedResults<T>()
        {
            Results = results,
            Page = pageNumber + 1,
            PageSize = pageSize,
            TotalCount = totalNumberOfRecords
        };
    }
}