Winform Application Exits Randomly

Question

I have a Winform application which crashes randomly. The application uses HtmlAgility's WebClient to parse the html page and download the images from a web server. I try to use Try-Catch but the application does not provide me other exceptions which can tell me what causes the crash, except for "500 internal server error". Here are some information. Could anyone can help me find the problem?

Thanks,

    'ReImageApp.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_32\mscorlib\v4.0_4.0.0.0__b77a5c561934e089\mscorlib.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'ReImageApp.exe' (Managed (v4.0.30319)): Loaded 'C:\ReImageProcess\bin\Debug\ReImageApp.exe', Symbols loaded.
'ReImageApp.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Windows.Forms\v4.0_4.0.0.0__b77a5c561934e089\System.Windows.Forms.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'ReImageApp.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Drawing\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Drawing.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'ReImageApp.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System\v4.0_4.0.0.0__b77a5c561934e089\System.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'ReImageApp.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Configuration\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Configuration.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'ReImageApp.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Xml\v4.0_4.0.0.0__b77a5c561934e089\System.Xml.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'ReImageApp.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\assembly\GAC_MSIL\Microsoft.VisualStudio.Debugger.Runtime\10.0.0.0__b03f5f7f11d50a3a\Microsoft.VisualStudio.Debugger.Runtime.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
'ReImageApp.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Core\v4.0_4.0.0.0__b77a5c561934e089\System.Core.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
The thread '<No Name>' (0x27d0) has exited with code 0 (0x0).
The thread '<No Name>' (0x2148) has exited with code 0 (0x0).
The thread '<No Name>' (0x26e4) has exited with code 0 (0x0).
The thread '<No Name>' (0x2998) has exited with code 0 (0x0).
The thread '<No Name>' (0x1484) has exited with code 0 (0x0).
The thread '<No Name>' (0x239c) has exited with code 0 (0x0).
'ReImageApp.exe' (Managed (v4.0.30319)): Loaded 'C:\ReImageProcess\bin\Debug\HtmlAgilityPack.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x10e0) has exited with code 0 (0x0).
The thread '<No Name>' (0x2acc) has exited with code 0 (0x0).
The thread '<No Name>' (0x2904) has exited with code 0 (0x0).
The thread '<No Name>' (0x230c) has exited with code 0 (0x0).
The thread '<No Name>' (0xecc) has exited with code 0 (0x0).
The thread '<No Name>' (0x2adc) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x1f18) has exited with code 0 (0x0).
The thread '<No Name>' (0x24e4) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x205c) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x26c0) has exited with code 0 (0x0).
The thread '<No Name>' (0x2700) has exited with code 0 (0x0).
The thread '<No Name>' (0x1fc0) has exited with code 0 (0x0).
The thread '<No Name>' (0x2534) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2168) has exited with code 0 (0x0).
The thread '<No Name>' (0x2bd0) has exited with code 0 (0x0).
The thread '<No Name>' (0x2754) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x22e0) has exited with code 0 (0x0).
The thread '<No Name>' (0x2a50) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2bdc) has exited with code 0 (0x0).
The thread '<No Name>' (0x1c14) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x23d0) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x1174) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x11f4) has exited with code 0 (0x0).
The thread '<No Name>' (0x1ab8) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2a38) has exited with code 0 (0x0).
The thread '<No Name>' (0x2674) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x16e8) has exited with code 0 (0x0).
The thread '<No Name>' (0x2710) has exited with code 0 (0x0).
The thread '<No Name>' (0x22f0) has exited with code 0 (0x0).
The thread '<No Name>' (0xd58) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0xf34) has exited with code 0 (0x0).
The thread '<No Name>' (0x1e80) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2be4) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x1178) has exited with code 0 (0x0).
The thread '<No Name>' (0x1724) has exited with code 0 (0x0).
The thread '<No Name>' (0x2370) has exited with code 0 (0x0).
The thread '<No Name>' (0x2b90) has exited with code 0 (0x0).
The thread '<No Name>' (0x2434) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2b4c) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x26d8) has exited with code 0 (0x0).
The thread '<No Name>' (0xb2c) has exited with code 0 (0x0).
The thread '<No Name>' (0x1428) has exited with code 0 (0x0).
The thread '<No Name>' (0x1138) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x1b0) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2228) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x22c4) has exited with code 0 (0x0).
The thread '<No Name>' (0x1670) has exited with code 0 (0x0).
The thread '<No Name>' (0x166c) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2828) has exited with code 0 (0x0).
The thread '<No Name>' (0x28c0) has exited with code 0 (0x0).
The thread '<No Name>' (0x1160) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x1d14) has exited with code 0 (0x0).
The thread '<No Name>' (0x12b8) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x1b48) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2274) has exited with code 0 (0x0).
The thread '<No Name>' (0x1ca0) has exited with code 0 (0x0).
The thread '<No Name>' (0x904) has exited with code 0 (0x0).
The thread '<No Name>' (0x16f0) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2928) has exited with code 0 (0x0).
The thread '<No Name>' (0x4b8) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x261c) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x1f20) has exited with code 0 (0x0).
The thread '<No Name>' (0x2a14) has exited with code 0 (0x0).
The thread '<No Name>' (0x1ecc) has exited with code 0 (0x0).
The thread '<No Name>' (0x2814) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x27a0) has exited with code 0 (0x0).
The thread '<No Name>' (0x181c) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2a30) has exited with code 0 (0x0).
The thread '<No Name>' (0x2a18) has exited with code 0 (0x0).
The thread '<No Name>' (0x26c4) has exited with code 0 (0x0).
The thread '<No Name>' (0x11e0) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x247c) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2960) has exited with code 0 (0x0).
The thread '<No Name>' (0x262c) has exited with code 0 (0x0).
The thread '<No Name>' (0x114c) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2a80) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x254c) has exited with code 0 (0x0).
The thread '<No Name>' (0x1898) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
The thread '<No Name>' (0x2a54) has exited with code 0 (0x0).
The thread '<No Name>' (0x2a78) has exited with code 0 (0x0).
The thread '<No Name>' (0x2bc0) has exited with code 0 (0x0).
The thread '<No Name>' (0x2690) has exited with code 0 (0x0).
The thread '<No Name>' (0x201c) has exited with code 0 (0x0).
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in System.dll
A first chance exception of type 'System.IO.DirectoryNotFoundException' occurred in mscorlib.dll
The program '[10296] ReImageApp.exe: Managed (v4.0.30319)' has exited with code 0 (0x0).

Update:

Here is the main lib -

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.IO;
using System.Threading;
using System.Configuration;
using System.ComponentModel;
using System.Text.RegularExpressions;
using HtmlAgilityPack;
using System.Drawing;
using ImageManipulation;
using System.Drawing.Imaging;

namespace ReImageApp
{
    class DownLoadImages
    {
        TextWriter tw2;
        object objLocker = new object();
        Dictionary<string, string> dc = new Dictionary<string, string>();
        private Queue<string> _downloadImageUrls = new Queue<string>();
        private Queue<string> _loggerQueue = new Queue<string>();

        public DownLoadImages()
        {

        }

        public DownLoadImages(TextWriter tw)
        {
            tw2 = tw;
        }

        public void AddImage2Queue(string url, string path)
        {
            _downloadImageUrls.Enqueue(url);
            dc.Add(url, path);
        }


        public void RunHtmlAgilityPackThread(string url)
        {
            try
            {
                Thread.Sleep(Convert.ToInt16(ConfigurationManager.GetAppSetting("PauseTime")) * 1000);
                WebClient linkclient = new WebClient();
                linkclient.DownloadDataCompleted += DownloadDataCompleted;
                linkclient.DownloadDataAsync(new Uri(url), url);
            }
            catch (Exception ex)
            {
                    _loggerQueue.Enqueue("Error in RunHtmlAgilityPackThread for url -- " + url + "  " + (ex.InnerException == null? "" : ex.InnerException.Message));
            }
        }

        private void DownloadDataCompleted(object sender,
            DownloadDataCompletedEventArgs e)
        {
            var url = (string)e.UserState;

            try
            {
                byte[] dbytes = e.Result;

                string responseStr = System.Text.Encoding.ASCII.GetString(dbytes);
                HtmlAgilityPack.HtmlDocument document = new HtmlAgilityPack.HtmlDocument();
                document.LoadHtml(responseStr);

                if (document.DocumentNode != null)
                {
                    IList<string> ilImages = (document.DocumentNode.Descendants("img").Select(x => x.Attributes["src"].Value).Distinct().ToList());

                    if (ilImages.Count == 0)
                    {
                            _loggerQueue.Enqueue("Warning (contains not image) in RunHtmlAgilityPackThread-- " + url);

                        return;
                    }

                    GetImageUrls(ilImages, url);
                }
                else
                {
                        _loggerQueue.Enqueue("Warning (No Html doc node) in RunHtmlAgilityPackThread -- " + url);
                        return;
                }
            }
            catch (WebException wx)
            {
                    _loggerQueue.Enqueue("Error in RunHtmlAgilityPackThread -- " + (wx.InnerException == null ? "" : wx.InnerException.Message) + " url --" + url);
            }
            catch (Exception ex)
            {
                    _loggerQueue.Enqueue("Error in RunHtmlAgilityPackThread -- " + (ex.InnerException == null ? "" : ex.InnerException.Message) + " url --" + url);
            }
        }


        private void GetImageUrls(IList<string> imgs, string url){
                    string url1, path;

                    try
                    {
                        for (int i = 0; i < imgs.Count; i++)
                        {
                            url1 = imgs[i].Replace("&amp;", "&");

                            if (url1.ToLower().Contains("image1") || url1.ToLower().Contains("image2"))
                            {
                                lock (objLocker)
                                {
                                    path = GetPath(url1, url);
                                    if (url1 != null)
                                    {
                                        _downloadImageUrls.Enqueue(url1);
                                        if (path != null)
                                            dc.Add(url1, path);
                                    }
                                }
                                DownloadFile();

                            }
                        }
                    }
                    catch (Exception ex)
                    {
                            _loggerQueue.Enqueue("Error in GetImageUrls -- " + (ex.InnerException == null ? "" : ex.InnerException.Message));
                    }
            }

        public void DownloadFile()
        {
            if (_downloadImageUrls.Any())
            {
                try
                {
                            WebClient imageclient = new WebClient();
                            imageclient.DownloadFileCompleted += client_DownloadFileCompleted;

                            var url = _downloadImageUrls.Dequeue();
                            string FileName = dc[url];

                            CreateDirectory(Path.GetDirectoryName(FileName));
                            imageclient.DownloadFileAsync(new Uri(url), FileName, FileName + " " + url);
                }
                catch (Exception ex)
                {
                        _loggerQueue.Enqueue("Error in DownloadFile -- " + (ex.InnerException == null ? "" : ex.InnerException.Message));
                }
                return;
            }

            // End of the download
            return;
        }

        private void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
        {
            string filenameurl = string.Empty;

            try
            {
                filenameurl = (string)e.UserState;

                _loggerQueue.Enqueue(filenameurl);

                if (e.Error != null)
                {
                    _loggerQueue.Enqueue("Error in client_DownloadFileCompleted -- " + (e.Error.InnerException == null ? "" : e.Error.InnerException.Message));
                }
                if (e.Cancelled)
                {
                    // handle cancelled scenario
                }
            }
            catch (Exception ex)
            {
            }

            try
            {
                while(_loggerQueue.Count>0)
                    tw2.WriteLine(_loggerQueue.Dequeue());

                DownloadFile();
            }
            catch (Exception ex)
            {
                _loggerQueue.Enqueue("Error in tw2.WriteLine -- " + (ex.InnerException == null? "" : ex.InnerException.Message));
            }
            //mre.Set();
        }


        private string GetPath(string url, string origUrl)
        {
            string strDestRoot = (string)ConfigurationManager.GetAppSetting("DestRoot");
            StringBuilder sb = new StringBuilder(strDestRoot);
            StringBuilder sbFile = new StringBuilder();
            string strTableOrChart;
            string strConcept;
            string strSTCode;
            string strCYCode;
            string strGridCount;
            string strMSCode;

            try
            {
                string[] strParam0 = origUrl.Replace("&amp;", "&").Replace("&quot;", "").Split(new string[] { "?", "_Type=", "&Parameter1=", "&Parameter2=", "&" }, StringSplitOptions.RemoveEmptyEntries);

                string[] strParam = url.Replace("&amp;", "&").Replace("&quot;", "").Split(new string[] { "?", "_Type=", "&Parameter1=", "&Parameter2=", "&" }, StringSplitOptions.RemoveEmptyEntries);

                strTableOrChart = strParam[1];
                sb.Append(@"\");
                sb.Append(strTableOrChart);

                strConcept = strParam0[2];
                sb.Append(@"\");
                sb.Append(strConcept);
                CreateDirectory(sb.ToString());
                sb.Append(@"\");
                sb.Append(strConcept);
                strSTCode = strParam[4];


                if (url.Contains("ImageCYTables?Table_Type=") || url.Contains("CYImage?Chart_Type="))
                {
                    strCYCode = strParam[5].Replace("Selected_CYCde=", "");
                    sb.Append(strCYCode);
                }
                else if (url.Contains("MSImage?Chart_Type=") || url.Contains("ImageMSTable?Table_Type="))
                {
                    strMSCode = strParam[5].Replace("Selected_MSCde=", "");
                    sb.Append(strMSCode);
                }
                else if (url.Contains("ImageTableMGrids?Table_Type="))
                {
                    if (strParam.Length > 5)
                    {
                        strGridCount = strParam[5].Replace("Parameter3=", "_");
                        sb.Append(strGridCount);
                    }
                    else
                        sb.Append(strSTCode);
                }
                else if (url.Contains("ImageCYTable_MGrids?Table_Type="))
                {
                    strCYCode = strParam[5].Replace("Selected_CYCde=", "");
                    strGridCount = strParam[6].Replace("Parameter3=", "_");
                    sb.Append(strCYCode);
                    sb.Append(strGridCount);
                }
                else
                    sb.Append(strSTCode);

                sb.Append(".png");
                return sb.ToString().Replace("\"", "");
            }
            catch (Exception ex)
            {
                //lock (tw2)
                {
                    _loggerQueue.Enqueue("Error in getpath -- " + (ex.InnerException == null ? "" : ex.InnerException.Message));
                }
                return null;
            }
        }

        private bool CreateDirectory(string path)
        {
            lock (objLocker)
            {
                if (!Directory.Exists(path))
                {
                    // Try to create the directory.
                    DirectoryInfo di = Directory.CreateDirectory(path);
                    return false;
                }
                else
                    return true;
            }
        }
    }
}

The Part to use the lib is -

                var doImages = GetDownLoadImagesThread();

                foreach (var aURL in iAllUrls.Distinct())
                {
                    doImages.Value.RunHtmlAgilityPackThread(aURL.Replace("&", "&").Replace("\"",""));
                }


private ThreadLocal<DownLoadImages> GetDownLoadImagesThread()
{
    TextWriter tw2 = new StreamWriter(CreateURLFile(2));
    tw2 = TextWriter.Synchronized(tw2);

    return new ThreadLocal<DownLoadImages>(() => new DownLoadImages(tw2));
}

Answer 1

"500 internal server error" is a server-side error. The error is occurring on your server, and it's sending a result 500 to your client. This causes an exception in the WinForms client. Your WinForms client is not coded with sufficient exception handling. Improve the exception handling on the client to gracefully handle exceptions. Look at your server to determine why the 500 error is occurring.