System.Data.Select.FindFirstMatchingRecord C# (CSharp) Method

        private int FindFirstMatchingRecord()
        {
            int rec = -1;
            int lo = 0;
            int hi = _index.RecordCount - 1;
            while (lo <= hi)
            {
                int i = lo + hi >> 1;
                int recNo = _index.GetRecord(i);
                int c = Evaluate(recNo);
                if (c == 0) { rec = i; }
                if (c < 0) lo = i + 1;
                else hi = i - 1;
            }
            return rec;
        }