public class Solution    {        public string MostCommonWord(string paragraph, string[] banned)        {            //"a, a, a, a, b,b,b,c, c"            paragraph = paragraph.ToLower().Replace("!", " ").Replace("?", " ").Replace("'", " ").Replace(",", " ").Replace(";", " ").Replace(".", " ");            var list = paragraph.Split(' ');            var dic = new Dictionary
     
      ();            foreach (var l in list)            {                var temp = l.Trim();                if (temp.Length == 0)                {                    continue;                }                var filter = banned.Where(x => x == temp).ToList();                if (filter.Count > 0)                {                    continue;                }                if (!dic.ContainsKey(temp))                {                    dic.Add(temp, 1);                }                else                {                    dic[temp]++;                }            }            var result = dic.OrderByDescending(x => x.Value).ToList().FirstOrDefault();            return result.Key;        }    }