Jackett/src/Jackett.Common/Models/TorznabCatType.cs

using System.Collections.Generic;
using System.Linq;

namespace Jackett.Common.Models
{
    public static partial class TorznabCatType
    {

        public static bool QueryContainsParentCategory(int[] queryCats, ICollection<int> releaseCats)
        {
            //return (from releaseCat in releaseCats
            //        select AllCats.FirstOrDefault(c => c.ID == releaseCat)
            //        into cat
            //        where cat != null && queryCats != null
            //        select cat.SubCategories.Any(c => queryCats.Contains(c.ID)))
            //    .FirstOrDefault();
            // Is equal to:

            foreach (var releaseCat in releaseCats)
            {
                var cat = AllCats.FirstOrDefault(c => c.ID == releaseCat);
                if (cat != null && queryCats != null)
                {
                    return cat.SubCategories.Any(c => queryCats.Contains(c.ID));
                }
            }

            return false;
        }

        public static string GetCatDesc(int newznabcat) =>
            AllCats.FirstOrDefault(c => c.ID == newznabcat)?.Name
            ?? string.Empty;

        public static string NormalizeCatName(string name) => name.Replace(" ", "").ToLower();

        public static TorznabCategory GetCatByName(string name) => AllCats.FirstOrDefault(c => NormalizeCatName(c.Name) == NormalizeCatName(name));
    }
}