统计字符出现的次数

        static void ReturnShowCOunt(string inputStr)
        {
            if (string.IsNullOrEmpty(inputStr))
                throw new ArgumentNullException("inputStr");

            for (int i = 0; i < inputStr.Length; i++)
            {
                int flag = 0;
                int count = 1;

                for (int j = 0; j < i; j++)
                {
                    if (inputStr[i] == inputStr[j])
                    {
                        flag = 1;
                        break;
                    }                    
                }

                if (flag == 1)
                    continue;

                for (int k = i + 1; k < inputStr.Length; k++)
                {
                    if (inputStr[i] == inputStr[k])
                        count++;
                }

                Console.WriteLine("{0}:{1}", inputStr[i], count);
            }
        }