【C#】比较简单地获取随机数字或者字母

弄验证码或生成appkey应该会比较常用到

纯数字的：

 public static string GetCode(int length=4)
        {
            var code = new StringBuilder();
            var random = new Random();
            while (code.Length < length)
            {
                code.Append(random.Next(0,9));
            }        
            return code.ToString();
        }

带字母的:

        public string GetAppKeyString(int length)
        {
            StringBuilder result = new StringBuilder();
            string pool = "0123456789abcdefghijklnmopqrstuvwxyz";//数字+小写字母,可以加大写
            Random random = new Random();
            while (result.Length < length)
            {
                result.Append(pool[random.Next(0, pool.Length - 1)]);
            }
            return result.ToString();
        }