今天下午写两个函数，还是比较通用的~~~

        /**//// <summary>
        /// 产生由英文和数字组成的指定个数的随机数
        /// </summary>
        /// <param name="number">产生随机数的个数</param>
        /// <returns>指定个数的随机英数字符串</returns>
        public static string GetRandomCode(int number)
        {
            string[] arrList = new string[] {"0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F","G",
                                            "H","I","J","K","L","M","N","O","P","Q","R","S","T","U","W","X","Y","Z"} ;
            StringBuilder sb = new StringBuilder("") ;
            Random random = new Random() ;

            for( int i = 0 ; i < number ; i++ )
            {
                sb.Append(arrList[(int)random.Next(0,arrList.Length)]) ;
            }

            return sb.ToString() ;
        }

        /**//// <summary>
        /// 判断号码是联通，移动，电信中的哪个,在使用本方法前，请先验证号码的合法性
        /// 规则：前三位为130-133 联通 ；前三位为135-139或前四位为1340-1348 移动； 其它的应该为电信
        /// </summary>
        /// <param name="mobile">要判断的号码</param>
        /// <returns>返回相应类型：1代表联通；2代表移动；3代表电信</returns>
        public static int GetMobileType(string mobile) 
        {
            string[] chinaUnicom  = new string[] {"130","131","132","133"} ;
            string[] chinaMobile1 = new string[] {"135","136","137","138","139"} ;
            string[] chinaMobile2 = new string[] {"1340","1341","1342","1343","1344","1345","1346","1347","1348"} ;

            bool bolChinaUnicom  = (Array.IndexOf(chinaUnicom,mobile.Substring(0,3)) >= 0) ;
            bool bolChinaMobile1 = (Array.IndexOf(chinaMobile1,mobile.Substring(0,3)) >=0) ;
            bool bolChinaMobile2 = (Array.IndexOf(chinaMobile2,mobile.Substring(0,4)) >=0) ;

            if (bolChinaUnicom)
                return 1  ;//联通

            if ( bolChinaMobile1 || bolChinaMobile2 )
                return 2 ; //移动
            
            return 3 ; //其他为电信
        }

注：有朋友建议，第二方法用正则表达式实现更好，确实不错，下面把第二方法的新实现贴上:

        /**//// <summary>
        /// 判断号码是联通，移动，电信中的哪个,在使用本方法前，请先验证号码的合法性
        /// 规则：前三位为130-133 联通 ；前三位为135-139或前四位为1340-1348 移动； 其它的应该为电信
        /// </summary>
        /// <param name="mobile">要判断的号码</param>
        /// <returns>返回相应类型：1代表联通；2代表移动；3代表电信</returns>
        public static int GetMobileType(string mobile)
        {
            if (IsChinaUnicomNumber(mobile))
                return 1 ;

            if (IsChinaMobileNumber(mobile))
                return 2 ;

            return 3 ;
        }

        //是否是联通的号码 测试通过
        private static bool IsChinaUnicomNumber(string mobile)
        {
            string sPattern = "^(130|131|132|133)[0-9]{8}";
            bool isChinaUnicom = Regex.IsMatch(mobile,sPattern) ;

            return isChinaUnicom ;
        }

        //是否是移动的号码 测试通过
        private static bool IsChinaMobileNumber(string mobile) 
        {
            string sPattern = "^(135|136|137|138|139|1340|1341|1342|1343|1344|1345|1346|1347|1348)[1-9]{7,8}" ;

            return Regex.IsMatch(mobile,sPattern) ;
        }