Question

Class:

[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, InstanceContextMode = InstanceContextMode.PerSession)]
public class MainService : IChat
{
    IChatCallback ChatCallback = OperationContext.Current.GetCallbackChannel<IChatCallback>();
    Chat chat = new Chat(this);
    public void ShowChat()
    {
        chat.Show();
    }
    public void SendInstantMessage(string user, string message)
    {
        chat.RaiseMsgEvents(user, message);
        ChatCallback.InstantMessage(user, message);
    }
 }

Form:

public partial class Chat : Form
{
    MainService service;

    public Chat(MainService service)
    {
        InitializeComponent();
        OnMsgReceivedEvent += new OnMsgReceived(callback_OnMsgReceivedEvent);
        this.service = service;
    }

    private void btnSend_Click(object sender, EventArgs e)
    {
        service.SendInstantMessage("Admin", txtMsg.Text);
    }
 }

The mainForm use the class like this:

 public partial class Form1 : Form
 {
    ServiceHost host;
    public Form1()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        host = new ServiceHost(typeof(WCF_Server.MainService));
        host.Open();
    }
 }

In the main form, i just pass the class, no initializing, but in the class when ShowChat() called i need to show the chat form and get to this class method so i can send messages.

Answer 1

.NET is an object oriented language. In fact, every class is an object.

The error you are getting is because you’re instantiating an object with “this” on the global level.

UPDATE

Based on your update you could do the following and it will work. You might want to refactor this some more to ensure that it’s not going to break any business rules etc.

[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, InstanceContextMode = InstanceContextMode.PerSession)]
public class MainService : IChat
{
    IChatCallback ChatCallback = OperationContext.Current.GetCallbackChannel<IChatCallback>();
    //Changed this to be just a declaration. This will be null,
    // as there is no object yet, this is really just a pointer to nothing.
    //This tells the system that you might/are planning to use an object called 
    //chat, but it doesn't exist yet.
    Chat chat;

    // Get your default constructor going. This will create the actual chat object, allowing the rest of your class to access it.
    public MainService()
    {
         //instantiate it! (or as some of our co-ops say "We're newing it")
         chat = new Chat(this);
    }

    //now that chat is actually instantiated/created you can use it.
    public void ShowChat()
    {
        chat.Show();
    }
    public void SendInstantMessage(string user, string message)
    {
        chat.RaiseMsgEvents(user, message);
        ChatCallback.InstantMessage(user, message);
    }
 }

This is just a personal pet peeve, but having a function parameter the same name as a global variable is… well for me a no no. I noticed this on your Chat.Chat(MainService) function.