Friends Database, Using Files - C# Programming Exercise

// Importing necessary namespaces for file handling and basic C# functionalities
using System; // For basic Console operations
using System.IO; // For file handling
using System.Collections.Generic; // For using the List collection

public class Friend
{
    // Properties to store friend's details
    public string Name { get; set; } // Name of the friend
    public string PhoneNumber { get; set; } // Phone number of the friend
    public string Email { get; set; } // Email address of the friend

    // Constructor to initialize the friend's details
    public Friend(string name, string phoneNumber, string email)
    {
        Name = name;
        PhoneNumber = phoneNumber;
        Email = email;
    }

    // Method to return a string representation of the friend's data
    public override string ToString()
    {
        return $"{Name},{PhoneNumber},{Email}"; // Format the friend data to CSV (comma-separated)
    }

    // Static method to create a Friend object from a CSV formatted string
    public static Friend FromString(string str)
    {
        string[] parts = str.Split(','); // Split the string by commas
        return new Friend(parts[0], parts[1], parts[2]); // Return a new Friend object
    }
}

public class FriendsDatabase
{
    // List to store all friends
    private List friends;

    // File path to save and load friends data
    private string fileName;

    // Constructor that initializes the friends list and file name
    public FriendsDatabase(string fileName)
    {
        this.fileName = fileName;
        this.friends = new List();
        LoadFromFile(); // Attempt to load data from file at the start of the session
    }

    // Method to load friends from file if the file exists
    private void LoadFromFile()
    {
        if (File.Exists(fileName)) // Check if the file exists
        {
            string[] lines = File.ReadAllLines(fileName); // Read all lines from the file

            foreach (string line in lines)
            {
                if (!string.IsNullOrWhiteSpace(line)) // Skip empty lines
                {
                    friends.Add(Friend.FromString(line)); // Add each friend to the list
                }
            }
        }
    }

    // Method to save the current list of friends to the file
    public void SaveToFile()
    {
        using (StreamWriter writer = new StreamWriter(fileName))
        {
            foreach (var friend in friends)
            {
                writer.WriteLine(friend.ToString()); // Write each friend to the file
            }
        }
    }

    // Method to add a new friend to the database
    public void AddFriend(string name, string phoneNumber, string email)
    {
        friends.Add(new Friend(name, phoneNumber, email)); // Add the new friend to the list
    }

    // Method to display all friends in the database
    public void DisplayFriends()
    {
        if (friends.Count == 0)
        {
            Console.WriteLine("No friends to display."); // Notify if no friends are present
        }
        else
        {
            foreach (var friend in friends)
            {
                Console.WriteLine($"Name: {friend.Name}, Phone: {friend.PhoneNumber}, Email: {friend.Email}");
            }
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        string fileName = "friendsDatabase.txt"; // Define the file name to save/load data

        FriendsDatabase database = new FriendsDatabase(fileName); // Initialize the database with the file name

        while (true)
        {
            // Display the menu options
            Console.WriteLine("\nFriends Database");
            Console.WriteLine("1. Add Friend");
            Console.WriteLine("2. Display All Friends");
            Console.WriteLine("3. Exit");
            Console.Write("Choose an option: ");
            string choice = Console.ReadLine(); // Read user input

            if (choice == "1")
            {
                // Ask for friend's details to add
                Console.Write("Enter friend's name: ");
                string name = Console.ReadLine();
                Console.Write("Enter phone number: ");
                string phone = Console.ReadLine();
                Console.Write("Enter email address: ");
                string email = Console.ReadLine();

                // Add the new friend to the database
                database.AddFriend(name, phone, email);
                Console.WriteLine("Friend added successfully.");
            }
            else if (choice == "2")
            {
                // Display all friends
                database.DisplayFriends();
            }
            else if (choice == "3")
            {
                // Save data to file before exiting
                database.SaveToFile();
                Console.WriteLine("Data saved. Exiting the program...");
                break; // Exit the program
            }
            else
            {
                Console.WriteLine("Invalid option. Please try again.");
            }
        }
    }
}