C# .net Form1.visible from different class and thread

Question

I'm working on a client server application and this all works fine but since I programmed it so that when the client gets response from the server this is handled in a different class and thread. I would like to switch form1.Visible to be false from there (after login is successful). I tried many things like:

Trying to pass the form instance but was not able to get it there since the code happens as a reply from the server.

Making a function in Form1 that hides it and starts form2. this failed because I can't start that part from a different thread.

Finding the active form and hide that did not work either since I was not allowed to do that from a different thread.

How can i do something simple as hiding a form from a different class and thread?

the code:

public class ClientHandleData
{
    public static ByteBuffer playerBuffer;
    private delegate void Packet_(byte[] data);
    private static Dictionary<long, Packet_> packets = new Dictionary<long, Packet_>();
    private static long pLength;

    public static void InitMessages()
    {
        Console.WriteLine("Initializing network messages..");
        packets.Add((long)ServerPackets.SLoginCheckRes, Packet_Login_response);
    }

    public static void HandleData(byte[] data)
    {
        byte[] Buffer;
        Buffer = (byte[])data.Clone();

        if (playerBuffer == null) playerBuffer = new ByteBuffer();
        playerBuffer.WriteBytes(Buffer);

        if (playerBuffer.Count() == 0)
        {
            playerBuffer.Clear();
            return;
        }

        if (playerBuffer.Length() >= 8)
        {
            pLength = playerBuffer.ReadLong(false);
            if (pLength <= 0)
            {
                playerBuffer.Clear();
                return;
            }
        }

        if (playerBuffer.Length() >= 8)
        {
            pLength = playerBuffer.ReadLong(false);
            if (pLength <= 0)
            {
                playerBuffer.Clear();
                return;
            }
        }

        while (pLength > 0 & pLength <= playerBuffer.Length() - 8)
        {
            if (pLength <= playerBuffer.Length() - 8)
            {
                playerBuffer.ReadLong();
                data = playerBuffer.ReadBytes((int)pLength);
                HandleDataPackets(data);
            }
            pLength = 0;

            if (playerBuffer.Length() >= 8)
            {
                pLength = playerBuffer.ReadLong(false);
                if (pLength < 0)
                {
                    playerBuffer.Clear();
                    return;
                }
            }
        }
    }

    public static void HandleDataPackets(byte[] data)
    {
        long packetnum; ByteBuffer buffer; Packet_ packet;
        buffer = new ByteBuffer();
        buffer.WriteBytes(data);
        packetnum = buffer.ReadLong();
        buffer = null;

        if (packetnum == 0) return;

        if (packets.TryGetValue(packetnum, out packet))
        {
            packet.Invoke(data);
        }
    }

    private static void Packet_Login_response(byte[] data)
    {
        long packetnum; ByteBuffer buffer;
        buffer = new ByteBuffer(); ;
        buffer.WriteBytes(data);
        packetnum = buffer.ReadLong();
        string msg = buffer.ReadString();

        if(msg == "Wrong password")
        {
            System.Windows.Forms.MessageBox.Show("Wachtwoord is incorrect.");
        }
        else if(msg == "Wrong username")
        {
            System.Windows.Forms.MessageBox.Show("Gebruikersnaam is incorrect.");
        }
        else if(msg == "Login succes")
        {
            //here i want form1.visible to be false.
        }
    }
}

This script triggers when I click a login button on Form1. that starts loginclick on my networkmanager and that sends the data to the server. when the server replies the above code will run.

Answer 1

Your architecture is wrong. You have to have a reference to form1 somewhere. Possibly it should be as a interface.

In worst case scenario, you could pass it to ClientHandleData like:

public class ClientHandleData
{
  public static Form LoginForm { get; set; }
}

And at the beginning of your app:

ClientHandleData.LoginForm = form1;

And then if you want to close form from a different thread you should use Invoke:

static void DoHideLoginForm()
{
    LoginForm.Visible = false;
}

static void HideLoginForm()
{
    if(LoginForm.InvokeRequired)
        LoginForm.Invoke(new Action(() => DoHideLoginForm()));
    else
        DoHideLoginForm();
}

And then you just call HideLoginForm when you want to hide it. This code first checks if you're in a different thread (InvokeRequired) and calls DoHideLoginForm from a proper thread.

But your architecture is bad and it can bring you to more and more problems. I think that this should be done more like this:

• You should have a login controller class

• You should have login interface and login form, like

  public interface ILoginView: IDisposable
  {
      string Login {get; set;}
      string Pass {get; set;}
  
      DialogResult ShowDialog();
  }
  

Then your loginForm (form1) should implement this interface:

class LoginForm: Form, ILoginView
{
    //here go Login and Pass properties
}

And your controller should be like this:

class LoginController
{
    ILoginView loginView;

    public LoginController(ILoginView loginView)
    {
        this.loginView = loginView;
    }

    public async Task<bool> Login()
    {
        loginView.ShowDialog();
        bool result = await DoYourLoginProcedure(loginView.Login, loginView.Pass);
        if(result)
        {
           loginView.Hide(); //or possibly Dispose
        }
    }
}

And then in your entry point:

LoginForm loginForm = new LoginForm();
LoginController contr = new LoginController(loginForm);
if(!contr.Login())
  //exit application

Of course this is not ideal solution, but this is the way you should go. Read about MVC, IoC (inversion of control) and DI (dependency injection)