Can't update text box in UI from server thread

Question

I trying to write a server program with UI on c#. the server is called from background worker->saparated thread. In the server' i have to update the UI about what cient connected on what prot, and also some other parameters. I understand that i have to use the Invoke and i read about it, but somehow i can't implement it on my code. So here is my code, thanks ahead for any help:

enter code here


using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Runtime.InteropServices;
using System.Net.Sockets;
using System.Threading;
using System.IO;
using System.Configuration;
using System.Collections;



namespace WindowsFormsApplication1
{


    public partial class ServerAppMainDisplay : Form
    {
        public Int32 local_port = 40000;
        public int StopOrSrart = 0;
        public string localIP = "?";
        public string myHostName = "?";
        public string ServerIP = "Server IP: ";
        public string DefaultPort = "Listening on default port: ";
        public string MachineName = "Machine Name: ";
        public static bool ThrdState = false;
        public static bool TxtBoxVsblty = false; 

        public ServerAppMainDisplay()
        {
            InitializeComponent();
            textBox2.Text = DefaultPort;
            textBox1.Text = ServerIP;
            textBox3.Text = MachineName;
            textUpdate.ShowDialogs();
        }



        private void UpdateText(string text)
        {
            // Set the textbox text
            textBox5.Text = text;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            myHostName = Dns.GetHostName().ToString();
            localIP = Dns.Resolve(myHostName).AddressList[0].ToString();
            textBox1.Text = ServerIP + localIP;
            textBox3.Text = MachineName + myHostName;
            textBox2.Text = DefaultPort + local_port.ToString();
            backgroundWorker1.RunWorkerAsync();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            //Data Log txt
        }

        private void button3_Click(object sender, EventArgs e)
        {
            //Data Log Excel
        }

        private void button4_Click(object sender, EventArgs e)
        {
            DialogResult dialogResult = MessageBox.Show("Are you sure you want to stop server application?",
                "Stop server application", MessageBoxButtons.YesNo);
            if (dialogResult == DialogResult.Yes)
            {
                textBox2.Text = DefaultPort;
                textBox1.Text = ServerIP;
                textBox3.Text = MachineName;
                myTCPServer.thread.Abort();
                myTCPServer.listener.Stop();
                myTCPServer.DefSoc.Dispose();
                for (int i = 1; i < 10; i++)
                {
                    if (myTCPServer.Connection[i].portFlag)
                    {
                        myTCPServer.Connection[i].slistener.Stop();
                        myTCPServer.Connection[i].socket.Dispose();
                    }
                }
                ThrdState = true;
                TxtBoxVsblty = false;
            }
            if (dialogResult == DialogResult.No) return;
        }

        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            myTCPServer.myMain();
        }

        private void button5_Click(object sender, EventArgs e)
        {
            DialogResult dialogResult = MessageBox.Show("Are you sure you want to exit server window application?",
                "Exit server window application", MessageBoxButtons.YesNo);
            if (dialogResult == DialogResult.Yes)
            {
                backgroundWorker1.Dispose();
                backgroundWorker1.CancelAsync();
                myTCPServer.thread.DisableComObjectEagerCleanup();
                myTCPServer.thread.Abort();
                this.Close();
                Application.Exit();
            }
            if (dialogResult == DialogResult.No) return;
        }

    }
    public class myTCPServer
    {
        public static Socket DefSoc;
        public static Thread thread = new Thread(new ThreadStart(Service));
        public static TcpListener listener;
        public struct Connection_s
        {
            public int port;
            public bool portFlag;
            public Socket socket;
            public TcpListener slistener;
        };
        public static myTCPServer.Connection_s[] Connection = new myTCPServer.Connection_s[10];
        public const int DefaultPort = 40000;

        public static void myMain()
        {
            if (!WindowsFormsApplication1.ServerAppMainDisplay.ThrdState)
                myTCPServer.thread.Start();
            else
            {
                myTCPServer.thread = new Thread(new  ThreadStart(Service));
                myTCPServer.thread.Start();
            }
        }
        public static void Service()
        {

            for (int i = 1; i < 10; i++)
            {
                Connection[i].portFlag = false;
                Connection[i].port = DefaultPort + i;
            }
            myTCPServer.listener = new TcpListener(DefaultPort);
            myTCPServer.DefSoc = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            while (true)
            {
                byte[] SndBfr;
                string str;
               myTCPServer.listener.Start();
               if (myTCPServer.listener.Pending())
                {
                    DefSoc = myTCPServer.listener.AcceptSocket();
                for (int i = 1; i < 10; i++)
                {

                    if (Connection[i].portFlag == false)
                    {
                        Thread.Sleep(10);
                        str = "<" + Connection[i].port as string;
                        SndBfr = System.Text.Encoding.UTF8.GetBytes(str);
                        DefSoc.Send(SndBfr);
                        Thread.Sleep(10);
                        Connection[i].slistener = new TcpListener(Connection[i].port);
                        Connection[i].slistener.Start();
                        Connection[i].socket = Connection[i].slistener.AcceptSocket();
                        Connection[i].portFlag = true;
                        yourTextBox.Invoke(new UpdateTextCallback(this.UpdateText), 
                            new object[]{”Text generated on non-UI thread.”});
                        DefSoc.Disconnect(true);
                        DefSoc.Dispose();
                        myTCPServer.listener.Stop();
                        myTCPServer.listener = new TcpListener(DefaultPort);
                        myTCPServer.DefSoc = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                        break;
                    }
                    }
                }
                Thread.Sleep(10);
                for (int i = 1; i < 10; i++)
                {
                    if (Connection[i].portFlag == true)
                    {
                        int SndRslt = 0;

                        str = DateTime.Now.ToString(@"MM\/dd\/yyyy h\:mm tt");
                        try
                        {
                            SndRslt = Connection[i].socket.Send(System.Text.Encoding.UTF8.GetBytes("+" + str));
                        }
                        catch (SocketException) { }
                        if (SndRslt <= 0)
                        {
                            try
                            {
                                Connection[i].portFlag = false;
                                Connection[i].socket.Disconnect(true);
                                Connection[i].slistener.Stop();
                            }
                            catch (SocketException) { }
                        }
                    }
                }
            }
        }
    }
}

Answer 1

Change your UpdateText(string text) to this:

    private void UpdateText(string text)
    {
        if(textBox5.InvokeRequired)
        {
           Action a = () => UpdateText(text);
           Invoke(a);
        }
        else 
          textBox5.Text = text;
    }

This will invoke the textbox if required.

Invoke From MSDN

The Invoke method searches up the control's parent chain until it finds a control or form that has a window handle if the current control's underlying window handle does not exist yet. If no appropriate handle can be found, the Invoke method will throw an exception. Exceptions that are raised during the call will be propagated back to the caller.

Answer 2

Invoke a delegate to the function that updates the UI and use InvokeRequired in the function to check if the delegate needs to be called.

Example:

Imports System.Management



  Private watcher As New ManagementEventWatcher
//delegate to udater UI function
  Delegate Sub SetItemCallback(ByVal item As ListViewItem)

  Private item1 As ListViewItem

  Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    Dim query As New WqlEventQuery("Win32_ProcessStartTrace")
    watcher.Query = query
    AddHandler watcher.EventArrived, AddressOf EventWorker
    watcher.Start()

  End Sub

  'This method start when event arrived. It's invoked from another thead. (not UI thread)

  Public Sub EventWorker(ByVal sender As Object, ByVal e As System.Management.EventArrivedEventArgs)

    Try

      Dim mbo As ManagementBaseObject = e.NewEvent

      For Each p As PropertyData In mbo.Properties

        item1 = New ListViewItem(p.Name)

        If p.Value IsNot Nothing Then : item1.SubItems.Add(p.Value.ToString)

        Else : item1.SubItems.Add(String.Empty)

        End If

        'updates de UI

        Me.SetItem(item1)


      Next

    Catch ex As Exception

      Console.WriteLine(ex.Message)

    End Try

  End Sub

  'If InvokeRequired (no UI thread) create the delegate and invoke it else update the UI
  Private Sub SetItem(ByVal itm As ListViewItem)

    If Me.ListView1.InvokeRequired Then

      Dim d As New SetItemCallback(AddressOf SetItem)

      Me.Invoke(d, New Object() {itm})

    Else

      ListView1.Items.Add(itm)

    End If

  End Sub

  Private Sub Form1_FormClosed(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed

    watcher.Stop()

  End Sub

Answer 3

You should go for "MethodInvoker" for cross-thread [Moreover, to ensure the "Method" executes on GUI thread]

Maybe this could help:

MethodInvoker method = delegate{
        yourTextBox.Text = "the text you need";
    };
if (InvokeRequired) // You may skip this
    BeginInvoke(method);