Whether the length intercepted by the string class contains a number

 Enter the ID number, intercept birthday, output//370303199003053330//console.write ("Please enter the ID number:");            String id = console.readline (); if (ID. Length = =)//{//String year = ID.            Substring (6,4); String month = ID.            Substring (10,2); String day = ID.            Substring (12,2);            Console.WriteLine ("Your Birthday is:" +year+ "year" +month+ "month" +day+ "Day"); }//else//{//Console.WriteLine ("Wrong input!")            ");            }//console.readline (); Mailbox format//1. There is only one @//2. Cannot start with @//[email protected] and. Cannot be together//[emai            L protected] At least one of them.            5. Cannot end with.//console.write ("Please enter your email account:");            String mail = Console.ReadLine (); bool a = mail.            Contains ("@"); if (a = = true)//{//int b = mail.            IndexOf ("@"); int c = mail.     LastIndexOf ("@");       if (b = = c)//{//if (b! = 0)//{// String mail1 = mail.            Substring (b); if (mail1.            Contains (".")) {//int d = mail1.            IndexOf ("."); if (d! = 1)//{//int e = Mail1.            LastIndexOf ("."); if (E! = Mail1. LENGTH-1)//{//Console.WriteLine ("email format entered correctly!            ");                        }//else//{// Console.WriteLine ("Wrong input!            ");            }//}//Else//{ Console.WriteLine ("Wrong input!            ");           //                } }//else//{//Console.WriteLine (" Wrong input!            "); }//}//Else//{//CONSOLE.W Riteline ("Wrong input!            "); }//}//Else//{//Console.WriteLine ("Wrong input!")            "); }//}//else//{//Console.WriteLine ("Wrong input!")            ");            }//string s = "abcdefghijklmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ0123456789"; Random Number class//random ran = new random ();//Initialize//double a = ran.            Next (10); int B = ran.            Next (s.length);            Console.WriteLine (a);            Console.ReadLine ();            Random out verification code, control the input, judge whether the correct//string s = "abcdefghijklmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ0123456789"; Random ran = newRandom ();            String Biao = ""; for (int i = 1; I <= 4; i++)//{//Biao + = S.substring (ran.            Next (s.length), 1);            }//console.writeline (Biao);            Console.Write ("Please enter the Verification Code:");            String shu = Console.ReadLine (); if (Shu. ToLower () = = Biao. ToLower ())//{//Console.WriteLine ("Input correct!")            "); }//else//{//Console.WriteLine ("Input Error!            ");            }//console.readline ();            Console.clear ();            Console.WriteLine ("123");            Console.ReadLine ();            string s = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";            Random ran = new random ();            for (;;)                {String A = ""; for (int i = 1; I <= 4; i++) {A + = S.substring (RAN).                Next (s.length), 1); } COnsole.                WriteLine (a);                Console.WriteLine ("Please enter the Verification Code:");                String B = Console.ReadLine ();                    if (b.tolower () = = A.tolower ()) {Console.WriteLine ("input correct");                Break                    } else {console.clear ();                Console.WriteLine ("Input Error"); }} console.readline ();

Whether the length intercepted by the string class contains a number