Putting it together

C# course · Intermediate · Lesson 69/116

Combine the Library class with a console menu.

Putting it together with a console menu

In the final lesson we combine every piece behind a console menu. The user picks an option; if branches call either ListBooks or SearchByAuthor based on the choice. This makes every method reachable from one place.

We will simulate the menu with an int variable: int choice = 1; runs both branches in turn. In a real app you would read with Console.ReadLine, but here we keep the output deterministic by using a fixed value.

Deterministic menu output

For a testable app the output must be deterministic: every run gives the same result. To ensure this we set the menu choice to a fixed value: int choice = 1;. Then we set choice = 2; to enter the second branch too.

The first branch calls lib.ListBooks(); the second branch prints SearchByAuthor results in a foreach. So a single run shows both listing and search behavior. In a real menu, the value read from the user would run only one branch.

Exercise Call ListBooks and SearchByAuthor from a menu

In Main create a Library instance; add two books (one by Tolkien, one by Herbert). Print Console.WriteLine("Menu:") as a header. Set int choice = 1; and call if (choice == 1) lib.ListBooks();. Then set choice = 2; and inside if (choice == 2) use a foreach over lib.SearchByAuthor("Herbert") and print each result with Console.WriteLine("Found: " + b.Title).

Show example solution

"); write. int choice = 1; if (choice == 1) lib.ListBooks(); then choice = 2; if (choice == 2) { foreach (var b in lib.SearchByAuthor("Herbert")) Console.WriteLine("Found: " + b.Title); }.
Example solution:
using System;
using System.Collections.Generic;

class Book
{
    public string Title { get; set; }
    public string Author { get; set; }
    public bool IsBorrowed { get; set; }
}

class Member
{
    public string Name { get; set; }
    public int BorrowedCount { get; set; }
}

class Library
{
    private List<Book> _books = new List<Book>();
    private List<Member> _members = new List<Member>();

    public void AddBook(Book b) { _books.Add(b); }
    public void AddMember(Member m) { _members.Add(m); }

    public void ListBooks()
    {
        foreach (var b in _books)
        {
            Console.WriteLine(b.Title);
        }
    }

    public void Checkout(Member m, Book b)
    {
        if (!b.IsBorrowed)
        {
            b.IsBorrowed = true;
            m.BorrowedCount++;
        }
    }

    public void Return(Member m, Book b)
    {
        if (b.IsBorrowed)
        {
            b.IsBorrowed = false;
            m.BorrowedCount--;
        }
    }

    public List<Book> SearchByAuthor(string author)
    {
        var result = new List<Book>();
        foreach (var b in _books)
        {
            if (b.Author == author) result.Add(b);
        }
        return result;
    }
}

class Program
{
    static void Main()
    {
        var lib = new Library();
        lib.AddBook(new Book { Title = "The Hobbit", Author = "Tolkien" });
        lib.AddBook(new Book { Title = "Dune", Author = "Herbert" });
        Console.WriteLine("Menu:");
        int choice = 1;
        if (choice == 1) lib.ListBooks();
        choice = 2;
        if (choice == 2)
        {
            foreach (var b in lib.SearchByAuthor("Herbert"))
            {
                Console.WriteLine("Found: " + b.Title);
            }
        }
    }
}

The library app is ready

Congratulations! You finished the five-lesson library app. You now have Book and Member models, a Library class that manages them, a checkout flow, an author-based search and a console menu. This project shows how object-oriented C# fits together on a small example.

In the next groups we will dig deeper into generic classes and collections. You will learn how List<T> grows, how Dictionary hashes, and how to write your own iterators.

Test yourself

Which structure branches on the menu choice?
```
int choice = 1;
// ?
```
- if (choice == 1) { ... }
- foreach (choice) { ... }
- while (choice) { ... }
- return choice;
Show answer

if (choice == 1) { ... } — Correct. We branch with if based on the choice.
Match each menu piece to its job

if

Branches by choice
choice

Selection variable
ListBooks

Lists the books
SearchByAuthor

Filters by author

The equality check

if (choice ____ 1) lib.ListBooks();

Show answer

if (choice == 1) lib.ListBooks();

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Putting it together