Birleştirme

"); yaz. int choice = 1; if (choice == 1) lib.ListBooks(); sonra choice = 2; if (choice == 2) { foreach (var b in lib.SearchByAuthor("Oğuz Atay")) Console.WriteLine("Ara: " + b.Title); } yaz.
Örnek çözüm:
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 = "Çalıkuşu", Author = "Reşat Nuri" });
        lib.AddBook(new Book { Title = "Tutunamayanlar", Author = "Oğuz Atay" });
        Console.WriteLine("Menü:");
        int choice = 1;
        if (choice == 1) lib.ListBooks();
        choice = 2;
        if (choice == 2)
        {
            foreach (var b in lib.SearchByAuthor("Oğuz Atay"))
            {
                Console.WriteLine("Ara: " + b.Title);
            }
        }
    }
}