Retrieving a value in one class that is set in another

Question

I hope you are all doing well.

I've been having a small issue in a task for university, I have a variable in a class named Alpha where I want the value to be changed to what is entered by the user. For the second class named Charlie, I want to use the same value entered by the user. I understand why my work doesn't work but I have no idea if I am missing something fundamental to make it work.

This is just toy code and isn't my actual work however, this is an accurate reflection of the issue I'm having.

    class Alpha
    {
        public string message = "hello.";

        public void Bravo()
        {
            Charlie charlie = new Charlie();

            Console.WriteLine("Enter message here:");
            message = Console.ReadLine();

            Console.WriteLine("Alpha() says, " + message + ".");

            charlie.Delta();
        }
    }

    class Charlie
    {
        public void Delta()
        {
            Alpha alpha = new Alpha();

            Console.WriteLine("Charlie() says, " + alpha.message);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Alpha alpha = new Alpha();
            alpha.Bravo();
        }
    }

Answer 1

you need to pass the alpha instance to charlie

    charlie.Delta(this);

and

    public void Delta(Alpha alpha)
    {

        Console.WriteLine("Charlie() says, " + alpha.message);
    }

this is because you can have multiple different alphas with different messages. In your currebt code you creat a new alpha that has nothing to do with the one that called charlie.delta.

Another possibility is to have static data. In this case there is only one occurrence of it

class Alpha
{
    public static string message = "hello.";
    .....

    public void Bravo()
    {
        Charlie charlie = new Charlie();

        Console.WriteLine("Enter message here:");
        Alpha.message = Console.ReadLine();

        Console.WriteLine("Alpha() says, " + message + ".");

        charlie.Delta();
    }
}

and

    public void Delta()
    {
     

        Console.WriteLine("Charlie() says, " + Alpha.message);
    }

Answer 2

You could also extract the code to read/write the message in a third class and pass it as a dependency to Alpha and Charlie.

class Message
{
    private string _message = "hello.";

    public void Read()
    {
        Console.WriteLine("Enter message here:");
        _message = Console.ReadLine();
    }

    public void Write(string from)
    {
        Console.WriteLine($"{from}() says ,{_message}");
    }
}

And then update the rest like:

class Alpha
{
    private readonly Message _message;
    private readonly Charlie _charlie;

    public Alpha(Message message)
    {
        _message = message;
        _charlie = new Charlie(message);
    }

    public void Bravo()
    {
        _message.Write(nameof(Alpha));
        _charlie.Delta();
    }
}

class Charlie
{
    private readonly Message _message;

    public Charlie(Message message)
    {
        _message = message;
    }

    public void Delta()
    {
        _message.Write(nameof(Charlie));
    }
}

class Program
{
    static void Main(string[] args)
    {
        Message message = new Message();
        message.Read();
        
        Alpha alpha = new Alpha(message);
        alpha.Bravo();
    }
}