Joining a project with some crazy LINQ sorting statements and after refactoring by the team using a custom comparer we found out that it is so slow for some data that you actually think it is an infinite loop.How to fix this performance issue but still maintaining the sorting requirements?private static IEnumerable<PolicyTransactionItem<Subject>> GetSubjectsForChangeTracking(            List<PolicyTransaction> transactions)        {            var ebcidicSortComparer = new EBCDICSortComparer();            var subjects = (from t in transactions                            from s in t.PolicySubjects                            select new PolicyTransactionItem<Subject>()                            {                                Item = s,                                PolicyNumber = t.PolicyNumber,                                FromDate = t.EffectiveDate,                                ToDate = t.TermExpirationDate,                                CoverageKey = t.CoverageKey,                                AmBestNumber = t.IssuerAmBestCompanyNumber                            });            subjects = subjects                    .OrderBy(t => t.Item.FirstName, ebcidicSortComparer)                    .ThenBy(t => t.Item.MiddleName)                    .ThenBy(t => t.Item.LastName, ebcidicSortComparer)                    .ThenBy(t => t.Item.NameSuffix)                    .ThenBy(t => t.Item.DOB ?? DateTime.MaxValue)                    .ThenBy(t => t.Item.SSNFromDb, new EBCDICSortComparer(true))                    .ThenBy(t => t.Item.GenderCodeFromDb)                    .ThenBy(t => t.Item.RelationToInsuredCodeFromDb)                    .ThenBy(t => t.Item.RelationToPolicyHolderCodeFromDb)                    .ThenBy(t => t.Item.DLNumberFromDb, ebcidicSortComparer)                    .ThenBy(t => t.Item.DLStateFromDb, new EBCDICSortComparer(false))                    .ThenByDescending(t => t.FromDate)                    .ThenByDescending(t => t.ToDate).ToList();            return subjects;        }public class EBCDICSortComparer : IComparer<string>    {        public EBCDICSortComparer(bool emptyStringLast)        {            _emptyStringLast = emptyStringLast;        }        public EBCDICSortComparer()        {            _emptyStringLast = false;        }        private readonly bool _emptyStringLast;        static readonly int[] AsciiToEBCDICArray = new int[256]{                        0, 1, 2, 3, 55, 45, 46, 47, 22, 5, 37, 11, 12, 13, 14, 15,                        16, 17, 18, 19, 60, 61, 50, 38, 24, 25, 63, 39, 28, 29, 30, 31,                        64, 79,127,123, 91,108, 80,125, 77, 93, 92, 78,107, 96, 75, 97,                        240,241,242,243,244,245,246,247,248,249,122, 94, 76,126,110,111,                        124,193,194,195,196,197,198,199,200,201,209,210,211,212,213,214,                        215,216,217,226,227,228,229,230,231,232,233, 74,224, 90, 95,109,                        121,129,130,131,132,133,134,135,136,137,145,146,147,148,149,150,                        151,152,153,162,163,164,165,166,167,168,169,192,106,208,161, 7,                        32, 33, 34, 35, 36, 21, 6, 23, 40, 41, 42, 43, 44, 9, 10, 27,                        48, 49, 26, 51, 52, 53, 54, 8, 56, 57, 58, 59, 4, 20, 62,225,                        65, 66, 67, 68, 69, 70, 71, 72, 73, 81, 82, 83, 84, 85, 86, 87,                        88, 89, 98, 99,100,101,102,103,104,105,112,113,114,115,116,117,                        118,119,120,128,138,139,140,141,142,143,144,154,155,156,157,158,                        159,160,170,171,172,173,174,175,176,177,178,179,180,181,182,183,                        184,185,186,187,188,189,190,191,202,203,204,205,206,207,218,219,                        220,221,222,223,234,235,236,237,238,239,250,251,252,253,254,255                        };        public int Compare(string x, string y)        {            if (x == null)                return 1;            if (y == null)                return -1;            if (string.Equals(x, y))                return 0;            var xChars = x.ToCharArray();            var yChars = y.ToCharArray();            if (xChars.Length == 0)                return _emptyStringLast ? 1 : -1;            if (yChars.Length == 0)                return _emptyStringLast ? -1 : 1;            for (var i = 0; i < Math.Min(xChars.Length, yChars.Length); i++)            {                var charItemX = xChars[i];                var charItemY = yChars[i];                var ebcdicItemX = AsciiToEBCDICArray[charItemX];                var ebcdicItemY = AsciiToEBCDICArray[charItemY];                if (ebcdicItemX != ebcdicItemY)                    return ebcdicItemX > ebcdicItemY ? 1 : -1;            }            return x.Length.CompareTo(y.Length);        }    }[UPDATE]Debugging one by one the fields it turns out the problem is in .ThenBy(t => t.Item.SSNFromDb, new EBCDICSortComparer(true)). When I try to debug the comparer it seems that x and y are both null, always, and it turns out like a forever loop.Adding this at the top of the Compare method seems to fix the problem.if (string.IsNullOrWhiteSpace(x) &&    string.IsNullOrWhiteSpace(y))       return 0;
LINQ sorting using custom IComparer is very slow
c#;sorting;linq