计算字符串中每个字符出现的次数

 /// <summary>
        /// 计算每个字符出现的次数且打印
        /// </summary>
        /// <param name="str"></param>
        public void CharCount(string str)
        {
            Dictionary<char, int> dicCount = new Dictionary<char, int>();
            str = str.ToLower();
            foreach (char item in str.ToCharArray())
            {
                if (!Char.IsLetter(item))  
                    continue;
                if (!dicCount.ContainsKey(item))
                {
                    dicCount.Add(item, 1);
                }
                else
                {
                    dicCount[item]++;
                }
            }

            foreach (var item in dicCount.Keys)
            {
                Console.WriteLine("字符{0}:出现{1}次",item,dicCount[item]);
            }
        }