Console.WriteLine("请输入截止数字？退出请输入y");            string input = Console.ReadLine();            int n = Convert.ToInt32(input);            int count = 0; //计数            for (int i = 0; i <= n; i++)            {                string str = i.ToString();//要匹配的字符串                string pattern="1"; //要匹配的正则表达式模式                MatchCollection matches = Regex.Matches(str, pattern);  //正则表达式匹配验证                count += matches.Count;  //获得匹配数量，加到计数上，                //foreach (Match NextMatch in matches) //遍历获得数量也行，不过效率低                //{                //    count++;                //}            }            Console.WriteLine("在0-{0}中1出现了"+count+"次",input);