Threadpool.cs not found in win form

Question

i want write a chatroom with c# and Tcp but i have Threadpool.cs not found error.

how to can i fix this ? this is my code.

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 System.Net;
using System.Net.Sockets;
using System.Threading;

namespace Client
{
    public partial class Client : Form
    {
        Socket socClient = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

        public Client()
        {
            InitializeComponent();
        }

        private void btnConnect_Click(object sender, EventArgs e)
        {
            IPEndPoint ipServer = new IPEndPoint(IPAddress.Parse(txtIp.Text), int.Parse(txtPort.Text));
            socClient.Connect(ipServer);
        }
    }
}

you have the error in the screenshot. looks like you are accessing the ui components from a different thread. — EylM, Aug 16 '22 at 15:41
Does this answer your question? [Solve a cross-threading Exception in WinForms](https://stackoverflow.com/questions/5868783/solve-a-cross-threading-exception-in-winforms) — AliSalehi, Aug 16 '22 at 15:52
no when i use ``` socClient.Connect(ipServer); ``` i have this error. this not a ui |: @EylM — MahdiKarami, Aug 16 '22 at 15:54
That screenshot is because you have "Just My Code" debugging unticked in the Visual Studio options. "threadpool.cs" is not relevant here, it's the cross-threading that's the problem — Charlieface, Aug 16 '22 at 18:52

score 1 · Accepted Answer · answered Aug 16 '22 at 16:15

In Your Server Side Form1

you tried to update your list box from another thread so you faced this issue

on other to solve it you have to change your code from this :

void Accept(IAsyncResult res)
{
    socClient = socServer.EndAccept(res);
    listMessage.Items.Add("Client Connected...");
}

to this

        private delegate void UpdateListDelegate();
        void Accept(IAsyncResult res)
        {
            socClient = socServer.EndAccept(res);
            listMessage.Invoke(new UpdateListDelegate(() =>
            {
                listMessage.Items.Add("Client Connected...");
            }));
        }

so the main key is to Invoke your element whenever you are not working with main UI Thread.

`IAsyncResult` is ancient, you should use `Task` along with `async` `await` instead — Charlieface, Aug 16 '22 at 18:51
@Charlieface i agree,thats just another topic to talk about, just tried to give him the fastest solution based on his own code :D — AliSalehi, Aug 16 '22 at 20:20

score 0 · Answer 2 · answered Aug 16 '22 at 20:44

Your problem is that you have a cross-thread call. You can hack around that by using Invoke. But I would strongly advise you to switch to async await, which will maintain the current context.

 public partial class Client : Form
 {
     Socket socClient;

     public Client()
     {
         InitializeComponent();
     }

     private async void btnConnect_Click(object sender, EventArgs e)
     {
         socClient = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
         IPEndPoint ipServer = new IPEndPoint(IPAddress.Parse(txtIp.Text), int.Parse(txtPort.Text));
         await socClient.ConnectAsync(ipServer);
     }
 }

I also suggest you think about whether you want to use raw sockets, as it's much easier to use TcpClient.

Threadpool.cs not found in win form

2 Answers2