static void Main(string[] args) { int choose = 0; BookLibrary lib = new BookLibrary(); do { Console.WriteLine("1. Add New A Book"); Console.WriteLine("2. Update A Book"); Console.WriteLine("3. Delete A Book"); Console.WriteLine("4. Print Out All Book"); Console.WriteLine("5. Quit"); while (true) { try { Console.WriteLine("YOUR CHOCE: "); choose = int.Parse(Console.ReadLine()); if (choose <= 0 || choose > 5) { Console.WriteLine("Range between 1 and 5"); throw new Exception(); } break; } catch (Exception ex) { } } switch (choose) { case 1: lib.AddNewBook(); break; case 2: int IdToUpdate = 0; while (true) { try { Console.WriteLine("Input Book's Id: "); String BookId = Console.ReadLine(); for (int i = 0; i < BookId.Length; i++) { if (!Char.IsDigit(BookId[i])) { Console.WriteLine("Please input right number"); throw new Exception(); } } IdToUpdate = int.Parse(BookId); //if (checkId(id) == true) //{ // Console.WriteLine("Your id has been registed"); // throw new Exception(); //} break; } catch (Exception ex) { //Console.WriteLine(ex.Message); } } lib.UpdateBook(IdToUpdate); break; case 3: int IdToDelete = 0; while (true) { try { Console.WriteLine("Input Book's Id: "); String BookId = Console.ReadLine(); for (int i = 0; i < BookId.Length; i++) { if (!Char.IsDigit(BookId[i])) { Console.WriteLine("Please input right number"); throw new Exception(); } } IdToDelete = int.Parse(BookId); //if (checkId(id) == true) //{ // Console.WriteLine("Your id has been registed"); // throw new Exception(); //} break; } catch (Exception ex) { //Console.WriteLine(ex.Message); } } if (lib.checkId(IdToDelete)) { Console.WriteLine(" Do you want to delete that book ( YES to delete) "); String option = Console.ReadLine(); if (option.Equals("YES", StringComparison.OrdinalIgnoreCase)) { lib.DeleteBook(IdToDelete); } } break; case 4: lib.PrintAllBook(); break; case 5: default: Console.WriteLine("Google bye "); break; } }while (choose >= 1 && choose < 5); }