/// <summary>

       /// 判断输入的字符串是否只包含数字和英文字母

       /// </summary>

       /// <param name="input"></param>

       /// <returns></returns>

       public static bool IsNumAndEnCh(string input)

       {

           string pattern = @"^[A-Za-z0-9]+$";

           Regex regex = new Regex(pattern);

           return regex.IsMatch(input);

       }