static void ModifyClass() { int choice, id; string choiceTry, idTry; while (true) { while (true) { while (true) { Console.WriteLine("Please Enter Class ID: "); idTry = Console.ReadLine(); try { id = Int32.Parse(idTry); if (icb.ClassIsExists(id)) { break; } else { Console.WriteLine("This ID Is Not Exists! "); } } catch (Exception e) { Console.WriteLine("Please Enter A Number!"); continue; throw; } } Console.WriteLine( "////////////////////////////////////////////////////////////////////////////////////" + "\n" + "/* Modify Class */" + "\n" + "/* */" + "\n" + "/* */" + "\n" + "/* 1. Change Class ID */" + "\n" + "/* 2. Change Class Name */" + "\n" + "/* 3. Change Class Teacher Belong */" + "\n" + "/* 4. Exit */" + "\n" + "/* */" + "\n" + "/* Please Enter The Number */" + "\n" + "/* */" + "\n" + "////////////////////////////////////////////////////////////////////////////////////" + "\n"); choiceTry = Console.ReadLine(); try { choice = Int32.Parse(choiceTry); break; } catch (Exception e) { Console.WriteLine("Please Enter A Number!"); continue; throw; } } if (choice == 1) { int newId; string newIdTry; while (true) { Console.WriteLine("Please Enter The New ID of Class: "); newIdTry = Console.ReadLine(); try { newId = Int32.Parse(newIdTry); if (icb.ChangeClassId(id, newId)) { Console.WriteLine("Class ID Changed Successful!"); } else { Console.WriteLine("Class ID Changed Error, New Class ID is Already Exists!"); } break; } catch (Exception e) { Console.WriteLine("Class ID Must Be A Number! "); continue; throw; } } } else if (choice == 2) { string newName; Console.WriteLine("Please Enter The New Name of Class: "); newName = Console.ReadLine(); icb.ChangeClassName(id, newName); Console.WriteLine("Class Name Changed Successful!"); } else if (choice == 3) { int newTeacherId; string newTeacherIdTry; while (true) { Console.WriteLine("Please Enter The Teacher ID: "); newTeacherIdTry = Console.ReadLine(); try { newTeacherId = Int32.Parse(newTeacherIdTry); if (itb.TeacherIsExists(newTeacherId)) { icb.ChangeClassTeacherBelong(id, newTeacherId); Console.WriteLine("Changed Class Teacher Belong Successful!"); } else { Console.WriteLine("The Teacher ID Is Not Exists!"); } break; } catch (Exception e) { Console.WriteLine("Teacher ID Must Be A Number!"); continue; throw; } } } else if (choice == 4) { break; } else { Console.WriteLine("This Choice is Not Exists! "); } Work(); } }