查找字符串中出现频率最高的字符和次数

string str = @"dsssaa";

            var result1 = (from p in str.ToCharArray()
                      group p by p into gr
                      orderby gr.Count() descending
                      select new
                      {
                          CharKey = gr.Key,
                          CharCount = gr.Count()
                      }
                      ).FirstOrDefault();

            if (result1 != null)
            {
                Console.WriteLine("CharKey:" + result1.CharKey.ToString());
                Console.WriteLine("CharCount:" + result1.CharCount.ToString());
            }
           

            var result2 = str.ToCharArray().GroupBy(p=>p)
                .OrderByDescending(p=>p.Count())
                .Select(p=>new {CharKey=p.Key,CharCount=p.Count()})
                .FirstOrDefault();
            if (result2 != null)
            {
                Console.WriteLine("CharKey:" + result2.CharKey.ToString());
                Console.WriteLine("CharCount:" + result2.CharCount.ToString());
            }

            Dictionary<char, int> dic = new Dictionary<char, int>();
            foreach (char ch in str.ToCharArray())
            {
                if (dic.Keys.Contains(ch))
                {
                    dic[ch]++;
                }
                else
                {
                    dic.Add(ch, 1);
                }
            }

            if (dic.Keys.Count > 0)
            {
                char charKey = dic.First().Key;
                int charCount = dic.First().Value;
                foreach(var item in dic)
                {
                    if (item.Value > charCount)
                    {
                        charKey = item.Key;
                        charCount = item.Value;
                    }
                }
                Console.WriteLine("CharKey:" + charKey.ToString());
                Console.WriteLine("CharCount:" + charCount.ToString());
            }