// Solution Code

using System;

using System.Collections.Generic;

using System.Xml;

​

public class BookCatalog

{

    /// <summary>

    /// Reads an XML file representing a book catalog and extracts the titles of books published after the year 2000.

    /// </summary>

    /// <param name="xmlFilePath">The path to the XML file.</param>

    /// <returns>A list of book titles published after 2000. Returns an empty list if no books are found or if an error occurs.</returns>

    /// <exception cref="ArgumentException">Thrown when the input file path is null or empty.</exception>

    /// <exception cref="FileNotFoundException">Thrown when the XML file does not exist at the specified path.</exception>

    /// <exception cref="XmlException">Thrown when the XML file is invalid or malformed.</exception>

    public static List<string> GetTitlesPublishedAfter2000(string xmlFilePath)

    {

        // Validate input parameter

        if (string.IsNullOrEmpty(xmlFilePath))

        {

            throw new ArgumentException("The XML file path cannot be null or empty.", nameof(xmlFilePath));

        }

​

        if (!System.IO.File.Exists(xmlFilePath))

        {

            throw new System.IO.FileNotFoundException("The XML file does not exist.", xmlFilePath);

        }

​

        List<string> titles = new List<string>();

​

        try

        {

            XmlDocument doc = new XmlDocument();

            doc.Load(xmlFilePath);

​

            XmlNodeList bookNodes = doc.SelectNodes("/catalog/book");

​

            if (bookNodes != null)

            {

                foreach (XmlNode bookNode in bookNodes)

                {

                    XmlNode titleNode = bookNode.SelectSingleNode("title");

                    XmlNode yearNode = bookNode.SelectSingleNode("year");

​

                    if (titleNode != null && yearNode != null)

                    {

                        string title = titleNode.InnerText;

                        if (int.TryParse(yearNode.InnerText, out int year) && year > 2000)

                        {

                            titles.Add(title);

                        }

                    }

                }

            }

        }

        catch (XmlException ex)

        {

            throw new XmlException("The XML file is invalid.", ex);

        }

        catch (Exception ex)

        {

            // Handle other potential exceptions during file access or processing

            Console.WriteLine($"An error occurred: {ex.Message}");

            return new List<string>(); // Return an empty list in case of error.

        }

​

        return titles;

    }

​

    public static void Main(string[] args)

    {

        // Example usage:

        string xmlFilePath = "books.xml"; // Replace with your actual file path

​

        // Create a sample XML file (for demonstration purposes)

        string xmlContent = @"<?xml version=""1.0"" encoding=""utf-8""?>

<catalog>

  <book>

    <title>The Lord of the Rings</title>

    <author>J.R.R. Tolkien</author>

    <year>1954</year>

  </book>

  <book>

    <title>Harry Potter and the Philosopher's Stone</title>

    <author>J.K. Rowling</author>

    <year>1997</year>

  </book>

  <book>

    <title>The Hitchhiker's Guide to the Galaxy</title>

    <author>Douglas Adams</author>

    <year>1979</year>

  </book>

  <book>

    <title>The Name of the Wind</title>

    <author>Patrick Rothfuss</author>

    <year>2007</year>

  </book>

    <book>

    <title>A book after 2000</title>

    <author>An Author</author>

    <year>2020</year>

  </book>

</catalog>";

        System.IO.File.WriteAllText(xmlFilePath, xmlContent);

​

​

        try

        {

            List<string> titles = GetTitlesPublishedAfter2000(xmlFilePath);

​

            if (titles.Count > 0)

            {

                Console.WriteLine("Books published after 2000:");

                foreach (string title in titles)

                {

                    Console.WriteLine($"- {title}");

                }

            }

            else

            {

                Console.WriteLine("No books published after 2000 found.");

            }

        }

        catch (ArgumentException ex)

        {

            Console.WriteLine($"Error: {ex.Message}");

        }

        catch (System.IO.FileNotFoundException ex)

        {

            Console.WriteLine($"Error: {ex.Message}");

        }

        catch (XmlException ex)

        {

            Console.WriteLine($"Error: {ex.Message}");

        }

        catch (Exception ex)

        {

            Console.WriteLine($"An unexpected error occurred: {ex.Message}");

        }

    }

}