Game Score Tracker C#

```csharp
using System;
using System.Collections.Generic;
using System.Linq;

public class GameScoreTracker
{
    private Dictionary<string, int> playerScores;

    public GameScoreTracker()
    {
        playerScores = new Dictionary<string, int>();
    }

    public void AddPlayer(string playerName)
    {
        if (!playerScores.ContainsKey(playerName))
        {
            playerScores[playerName] = 0;
            Console.WriteLine($"Player '{playerName}' added.");
        }
        else
        {
            Console.WriteLine($"Player '{playerName}' already exists.");
        }
    }

    public void UpdateScore(string playerName, int scoreChange)
    {
        if (playerScores.ContainsKey(playerName))
        {
            playerScores[playerName] += scoreChange;
            Console.WriteLine($"Score updated for '{playerName}'. New score: {playerScores[playerName]}");
        }
        else
        {
            Console.WriteLine($"Player '{playerName}' not found.");
        }
    }

    public void DisplayScores()
    {
        if (playerScores.Count == 0)
        {
            Console.WriteLine("No players in the game.");
            return;
        }

        Console.WriteLine("Current Scores:");
        foreach (var player in playerScores.OrderByDescending(x => x.Value))
        {
            Console.WriteLine($"{player.Key}: {player.Value}");
        }
    }

    public string GetWinner()
    {
        if (playerScores.Count == 0)
        {
            return "No players in the game.";
        }

        var winner = playerScores.OrderByDescending(x => x.Value).FirstOrDefault();
        return $"The winner is '{winner.Key}' with a score of {winner.Value}!";
    }

    public static void Main(string[] args)
    {
        GameScoreTracker tracker = new GameScoreTracker();

        while (true)
        {
            Console.WriteLine("\nGame Score Tracker Menu:");
            Console.WriteLine("1. Add Player");
            Console.WriteLine("2. Update Score");
            Console.WriteLine("3. Display Scores");
            Console.WriteLine("4. Get Winner");
            Console.WriteLine("5. Exit");

            Console.Write("Enter your choice: ");
            string choice = Console.ReadLine();

            switch (choice)
            {
                case "1":
                    Console.Write("Enter player name: ");
                    string playerName = Console.ReadLine();
                    tracker.AddPlayer(playerName);
                    break;
                case "2":
                    Console.Write("Enter player name: ");
                    string updatePlayerName = Console.ReadLine();
                    Console.Write("Enter score change: ");
                    if (int.TryParse(Console.ReadLine(), out int scoreChange))
                    {
                        tracker.UpdateScore(updatePlayerName, scoreChange);
                    }
                    else
                    {
                        Console.WriteLine("Invalid score change. Please enter a number.");
                    }
                    break;
                case "3":
                    tracker.DisplayScores();
                    break;
                case "4":
                    Console.WriteLine(tracker.GetWinner());
                    break;
                case "5":
                    Console.WriteLine("Exiting...");
                    return;
                default:
                    Console.WriteLine("Invalid choice. Please try again.");
                    break;
            }
        }
    }
}
```