今天下午寫兩個函數，還是比較通用的~~~

        /**//// <summary>
        /// 產生由英文和數字組成的指定個數的隨機數
        /// </summary>
        /// <param name="number">產生隨機數的個數</param>
        /// <returns>指定個數的隨機英數字符串</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>
        /// 判斷號碼是聯通，移動，電信中的哪個,在使用本方法前，請先驗證號碼的合法性
        /// 規則：前三位爲130-133 聯通 ；前三位爲135-139或前四位爲1340-1348 移動； 其它的應該爲電信
        /// </summary>
        /// <param name="mobile">要判斷的號碼</param>
        /// <returns>返回相應類型：1代表聯通；2代表移動；3代表電信</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  ;//聯通

            if ( bolChinaMobile1 || bolChinaMobile2 )
                return 2 ; //移動
            
            return 3 ; //其他爲電信
        }

注：有朋友建議，第二方法用正則表達式實現更好，確實不錯，下面把第二方法的新實現貼上:

        /**//// <summary>
        /// 判斷號碼是聯通，移動，電信中的哪個,在使用本方法前，請先驗證號碼的合法性
        /// 規則：前三位爲130-133 聯通 ；前三位爲135-139或前四位爲1340-1348 移動； 其它的應該爲電信
        /// </summary>
        /// <param name="mobile">要判斷的號碼</param>
        /// <returns>返回相應類型：1代表聯通；2代表移動；3代表電信</returns>
        public static int GetMobileType(string mobile)
        {
            if (IsChinaUnicomNumber(mobile))
                return 1 ;

            if (IsChinaMobileNumber(mobile))
                return 2 ;

            return 3 ;
        }

        //是否是聯通的號碼 測試通過
        private static bool IsChinaUnicomNumber(string mobile)
        {
            string sPattern = "^(130|131|132|133)[0-9]{8}";
            bool isChinaUnicom = Regex.IsMatch(mobile,sPattern) ;

            return isChinaUnicom ;
        }

        //是否是移動的號碼 測試通過
        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) ;
        }