Losing values entered in the list after exiting the method (C#)

Question

Good night!

I started my learning in C# less than 3 weeks ago and I’m having trouble trying to manipulate lists. It’s a very simple console application.

I have a menu where the user selects between the options to include, edit and delete book records in the list, and also the option to print the list and clear the whole list. Each feature has a responsible method.

The problem is that when the 'Book' class records are included in the Insert() method, and when you go back to the menu and call the method to print the list, there is no output, as if the list were empty.

If I call the method to print the list within the method to include the records itself, all the values I entered in the list are displayed normally. What am I doing wrong?

                static  List <Book> Insert(){

                   List <Book>   bookList = new List<Book>();
                   Book books = new Book();

                   char reInsert;

                    do{

                    Console.Clear();

                    Console.WriteLine("Insira o titulo do livro: ");
                      
                      books.BookTitle=Console.ReadLine();

                    Console.WriteLine("Insira o nome do autor: ");
                      books.AuthorName=Console.ReadLine();
                    
                    Console.WriteLine("Insira a editora: ");
                        books.Publisher=Console.ReadLine(); 

                    Console.WriteLine("Insira o ano de lancamento: ");
                          books.ReleaseYear=Console.ReadLine();
               
                    Console.WriteLine("Insira o preco: ");
                          books.Price=decimal.Parse(Console.ReadLine());

                    Book book = new Book (books.BookTitle, books.AuthorName, books.Publisher, books.ReleaseYear, books.Price);

                    bookList.Add(book);

                    Console.WriteLine("Livro cadastrado com sucesso!");
                    Console.WriteLine("Deseja cadastrar outro livro? (S/N)");
                    reInsert=char.Parse(Console.ReadLine());
                    } while(reInsert=='s');

                    return bookList;
                                   
            }

  static void Print( List<Book> bookList){
             
             Console.Clear();

             var books = bookList.OrderBy(p => p.BookTitle);
          
                foreach(var b in books){

                    Console.WriteLine(@$"Titulo da Obra: {b.BookTitle}
                                         Autor: {b.AuthorName}
                                         Editora: {b.Publisher}
                                         Ano: {b.ReleaseYear}
                                         Valor: {b.Price}\n");
                }
                        Console.ReadLine();
                                                
                }
           }

Calling the methods:

 static bool menu = true;
        static void Main(string[] args)
        {  

            MainMenu();         
            
        }
         static void MainMenu(){
            
            do{
            Console.WriteLine("\t\t||eLib - v2.0||\n\n");

                Console.WriteLine("\t\tSelecione uma Opcao:\n");

                Console.WriteLine(@"
                
                1 - Cadastrar Livro

                2 - Editar Cadastro de Livro 

                3 - Remover um Livro

                4 - Limpar Base de Dados

                5 - Imprimir Livros Cadastrados

                6 - Sair
                
                "); 

                int index=int.Parse(Console.ReadLine());
                Options selectedOption = (Options)index;

                List<Book> bookList = new List<Book>();

                
                switch(selectedOption){

                case(Options.Insert):

                bookList =  Insert();

                break;

                case(Options.Print):

                Print(bookList);

                  break;

Hugs.

Answer 1

Note that you are creating a new list each time you select an option in the loop. To keep the desired list you should declare the list of books out of the repeat loop.

List<Book> bookList = new List<Book>();
static void MainMenu(){
    do{
        ...
    }
}

Within its function Insert, you also create a new list. Correct, in my view would be to pass your list by parameter:

static void Insert(List<Book> bookList)
{
    Book books = new Book();

    ...

    bookList.Add(book);
}

Note that the function is now of the type void because it will not return anything, just add a book to the list that was passed. The part of the switch would look like this:

switch (selectedOption)
{
    case(Options.Insert):
        Insert(livros);
        break;

    case(Options.Print):
        Print(livros);
        break;
}