private void AddStudent() { Console.WriteLine("--- Add Student ---"); Console.WriteLine("[optional] Enter Student Name: "); string name = Console.ReadLine(); if (name == null || name == "") { Console.WriteLine("Student Name is null!"); } else { newStu.StudentName = name; } Console.WriteLine("[optional] Enter Standard ID: "); InputID(); if (id == null) { Console.WriteLine("Standard ID is null!"); } else { newStu.StandardId = id; } bl.AddStudent(newStu); Console.WriteLine("Student has been added!"); Continue(); }