无法使用第三方提供的类通过嵌套类型访问外部类型XXX的非静态成员

Question

This problem has been addressed in SOF in general. However, I am unable (not competent enough) to apply the suggestions to this example. I am getting the "Cannot access a non-static member of outer type 'FixClientTest.Form1' via nested type ... " error. In this case, the nested type is an instantiation of a 3rd party provided class (in this case, the open-source QuickFix/n library). I understand that the source is not really relevant but I am trying to avoid any suggestion that might have me modifying that code and don't have the knowledge to get around the problem. My goal is simply to update form controls based on information that I get in the callbacks from this library. (The code below is just a simple form with 2 buttons, one to set up the event callbacks and the other to stop them.) I would greatly appreciate any suggestions that the community might have.

Thank You.

using System;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using QuickFix;

namespace FixClientTest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        public class MyQuickFixApp : QuickFix.IApplication
        {    
            public void FromApp(QuickFix.Message msg, SessionID sessionID) { }
            public void OnCreate(SessionID sessionID) { }
            public void OnLogout(SessionID sessionID) 
            {
                Console.WriteLine("Logged out.");
            }
            public void OnLogon(SessionID sessionID) 
            {
                Console.WriteLine("Logged In.");
            }
            public void FromAdmin(QuickFix.Message msg, SessionID sessionID) 
            {
                //logListView.Items.Add(msg.ToString()); <<GENERATES ERROR!

            }
            public void ToAdmin(QuickFix.Message msg, SessionID sessionID) { }
            public void ToApp(QuickFix.Message msg, SessionID sessionID) { }
        }

        public QuickFix.Transport.SocketInitiator _Initiator = null;

        private void connectButton_Click(object sender, EventArgs e)
        {
            string file = "c:/FIX/tradeclientIB.cfg";
            try
            {
                QuickFix.SessionSettings settings = new QuickFix.SessionSettings(file);
                QuickFix.IApplication myApp = new MyQuickFixApp();
                QuickFix.IMessageStoreFactory storeFactory = new QuickFix.FileStoreFactory(settings);
                QuickFix.ILogFactory logFactory = new QuickFix.ScreenLogFactory(settings);
                _Initiator = new QuickFix.Transport.SocketInitiator(myApp, storeFactory, settings, logFactory);   
                _Initiator.Start();

            }
            catch (System.Exception err)
            {
                MessageBox.Show(err.ToString());
            }
        }

        private void stopButton_Click(object sender, EventArgs e)
        {
            _Initiator.Stop();
        }
    }
}

Answer 1

Your MyQuickFixApp class doesn't know anything about the Form1 object.

First, I'd suggest moving it out of the Form1 class. Then, I'd look at how and when the MyQuickFixApp object is created. I'm not familiar with the QuickFix library, but a quick glance at the docs suggests that creating it in a button message handler isn't the right way to do this. (In a winforms app I'd imagine you'd create it in your Program.Main method).

As for the actual error, you need to give the MyQuickFixApp object a reference to the Form1 object (probably pass it in the constructor).

public class MyQuickFixApp : QuickFix.IApplication
{
    private readonly Form1 _form1;
    public MyQuickFixApp(Form1 form)
    {
       _form1 = form;
    }

    public void FromAdmin(QuickFix.Message msg, SessionID sessionID) 
    {
        _form1.logListView.Items.Add(msg.ToString());
    }
}

Answer 2

While I was waiting for answers, I took another look at an answer provided in this link: Property is inaccessible due to its protection level When I read it again more carefully this time, I realized that Steve had posted the answer I need so it is really his answer. I needed to restructure this using events to capture the change in the form and to preserve encapsulation. It also allowed me to move my class that updated the form out of the Form class, however, it created the much-feared "cross-thread" problem. I already had an answer for this from someone else (sorry, don't have that link). I added lines to the event that updates the form to spin it off as a new thread. I've done this before and it works nicely. If anyone thinks this might be a problem, please let me know. Apologies if I've wasted anyone's time in looking at my problem but I thought I would share the mix of answers because it solves two of the biggest problems I've had since learning c#/forms.

One thing, don't get confused about this declaration: private delegate void AddLogItemDelegate(string msg); It is related to creating the thread containing the AddLogItem function and not to the creation of the event.

Thanks

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using QuickFix;

namespace FixClientTest
{

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

        public QuickFix.Transport.SocketInitiator _Initiator = null;

        private void connectButton_Click(object sender, EventArgs e)
        {
            string file = "c:/FIX/tradeclientIB.cfg";
            try
            {
                QuickFix.SessionSettings settings = new QuickFix.SessionSettings(file);
                QuickFix.IApplication myApp = new MyQuickFixApp();
                QuickFix.IMessageStoreFactory storeFactory = new QuickFix.FileStoreFactory(settings);
                QuickFix.ILogFactory logFactory = new QuickFix.ScreenLogFactory(settings);
                //QuickFix.Transport.SocketInitiator initiator = new QuickFix.Transport.SocketInitiator(myApp, storeFactory, settings, logFactory);
                _Initiator = new QuickFix.Transport.SocketInitiator(myApp, storeFactory, settings, logFactory);

                MyQuickFixApp.UpdateEvent += new MyQuickFixApp.OnUpdateEvent(AddLogItem);
                _Initiator.Start();

            }
            catch (System.Exception err)
            {
                Console.WriteLine(err.Message);
                Console.WriteLine(err.StackTrace);
                MessageBox.Show(err.ToString());
            }
        }

        private void stopButton_Click(object sender, EventArgs e)
        {
            _Initiator.Stop();
        }
        public string stuff;

        private delegate void AddLogItemDelegate(string msg);
        public void AddLogItem(string msg)
        {
            if(this.InvokeRequired)
            {
                this.Invoke(new AddLogItemDelegate(AddLogItem), new object[] { msg });
                return;
            }

            try
            {
                logListView.Items.Add(msg);
            }
            catch(Exception err)
            {
                MessageBox.Show(err.ToString());
            }
        }
    }


    public class MyQuickFixApp : QuickFix.IApplication
    {

        public delegate void OnUpdateEvent(string msg);
        public static event OnUpdateEvent UpdateEvent;

        public void FromApp(QuickFix.Message msg, SessionID sessionID) { }
        public void OnCreate(SessionID sessionID) { }
        public void OnLogout(SessionID sessionID)
        {
            Console.WriteLine("Logged out.");
        }
        public void OnLogon(SessionID sessionID)
        {
            UpdateEvent("STUFF!!");
            Console.WriteLine("Logged In.");
        }
        public void FromAdmin(QuickFix.Message msg, SessionID sessionID)
        {

        }
        public void ToAdmin(QuickFix.Message msg, SessionID sessionID) { }
        public void ToApp(QuickFix.Message msg, SessionID sessionID) { }
    }


}