Question

I have a Form with two ListBoxes on them. I have removeFromBoxWaiting that watches for creating of new files in a directory.
Once a file is created it prints it out and then it should add the name of the file into the list box.
My problem is that the list box does not get updated. Items actually have been added but they do not show and i have tried update() as well but it didn’t work. So any tips will be appreciated. Thanks in advance.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Text;
using System.Windows.Forms;
using DevExpress.XtraBars;
using System.Threading;
using System.Configuration;

namespace PrntToKitchen
{
public partial class PrintFiles : DevExpress.XtraBars.Ribbon.RibbonForm
{
    FileSystemWatcher filesWatcher = new FileSystemWatcher();

    public void barButtonItem1_ItemClick(object sender, ItemClickEventArgs e)
    {          
        MessageBox.Show(e.Item.Name);
        if (Properties.Settings.Default[e.Item.Name + "Read"].ToString().Length > 1 && Properties.Settings.Default[e.Item.Name + "ExtIn"].ToString().Length > 1)
        {
            filesWatcher.Path = Properties.Settings.Default[e.Item.Name + "Read"].ToString();
            filesWatcher.Created += new System.IO.FileSystemEventHandler(eventG);
            //filesWatcher.Deleted += new System.IO.FileSystemEventHandler(addToBoxFinished);
            filesWatcher.EnableRaisingEvents = true;                    
        }
    }

    public void eventG(object sender, FileSystemEventArgs e)
    {
        string CurrentPrinter = "";
        string findPrt = e.FullPath.Substring(0, e.FullPath.Length-(e.Name.Length + 1));
        string findPrtExt = e.Name.Substring(e.Name.LastIndexOf("."));

        for (int i = 1; i <= Properties.Settings.Default.NumberOfPrinters; i++)
        {
            string testPrt = Properties.Settings.Default["Printer" + i + "Read"].ToString();
            string testExt = Properties.Settings.Default["Printer" + i + "ExtIn"].ToString();

            if (testPrt == findPrt && testExt == findPrtExt)
            {
                CurrentPrinter = "Printer" + i.ToString();
                POSPrinter printer = new POSPrinter(Properties.Settings.Default["Printer" + i + "Port"].ToString(), (int)Properties.Settings.Default["Printer" + i + "Speed"]);
                addToBoxWaiting(e.FullPath.ToString());
                string file = e.FullPath;
                printer.BeginPrint();
                printer.PrintFile(file);
                printer.EndPrint();
                printer.Dispose();
                if ((bool)Properties.Settings.Default[CurrentPrinter + "Delete"])
                {
                    IsFileLocked(file);
                    System.IO.File.Delete(file);
                }
                else
                {
                    System.IO.File.Move(file, Properties.Settings.Default[CurrentPrinter + "Store"] + "\\" + e.Name + Properties.Settings.Default[CurrentPrinter + "ExtOut"]);
                }
                removeFromBoxWaiting(e.FullPath.ToString());
                addToBoxFinished(e.FullPath.ToString());
                busy = false;
                break;
            }
        }
    }

    void addToBoxWaiting(string text)
    {
        listBox1.Items.Add(text);

    }

    void removeFromBoxWaiting(string text)
    {
        listBox1.Items.Remove(text);
    }

    public void addToBoxFinished(string destination)
    {
       listBox2.Items.Add(destination);

    }

}

}

Answer 1

I believe your problem is that you are trying to add/remove listbox items while iterating through a loop (and both this actions are happening on UI thread). You should move your for loop into a separate thread, and your addToBoxWaiting method will then look like this:

private void AddToListBox(string item)
{
    MethodInvoker del = delegate
    {
        listBox1.Items.Add(item);
    };
    BeginInvoke(del);
}

Edit. Added thread code.

    public void eventG(object sender, FileSystemEventArgs e)
    {
        Thread eventThread = new Thread(ThreadProcEventG);
        eventThread.Start(e);
    }

    private void ThreadProcEventG(object eventArgs)
    {
        var e = (FileSystemEventArgs)eventArgs;
        string CurrentPrinter = "";
        string findPrt = e.FullPath.Substring(0, e.FullPath.Length-(e.Name.Length + 1));
        string findPrtExt = e.Name.Substring(e.Name.LastIndexOf("."));

        for (int i = 1; i <= Properties.Settings.Default.NumberOfPrinters; i++)
        {
            string testPrt = Properties.Settings.Default["Printer" + i + "Read"].ToString();
            string testExt = Properties.Settings.Default["Printer" + i + "ExtIn"].ToString();

            if (testPrt == findPrt && testExt == findPrtExt)
            {
                CurrentPrinter = "Printer" + i.ToString();
                POSPrinter printer = new POSPrinter(Properties.Settings.Default["Printer" + i + "Port"].ToString(), (int)Properties.Settings.Default["Printer" + i + "Speed"]);
                addToBoxWaiting(e.FullPath.ToString());
                string file = e.FullPath;
                printer.BeginPrint();
                printer.PrintFile(file);
                printer.EndPrint();
                printer.Dispose();
                if ((bool)Properties.Settings.Default[CurrentPrinter + "Delete"])
                {
                    IsFileLocked(file);
                    System.IO.File.Delete(file);
                }
                else
                {
                    System.IO.File.Move(file, Properties.Settings.Default[CurrentPrinter + "Store"] + "\\" + e.Name + Properties.Settings.Default[CurrentPrinter + "ExtOut"]);
                }
                removeFromBoxWaiting(e.FullPath.ToString());
                addToBoxFinished(e.FullPath.ToString());
                busy = false;
                break;
            }
        }
    }