I have a little problem with my data processing. public void ParseDetails() { for (int i = 0; i < mListAppInfo.Count; ++i) { ParseOneDetail(i); } } For 300 records, it usually takes around 13-15 minutes. I've tried to improve by using Parallel.For() but it always stop at some point. public void ParseDetails() { Parallel.For(0, mListAppInfo.Count, i => ParseOneDetail(i)); } In method ParseOneDetail(int index), I set an output log for tracking the record id which is under processing. Always hang at some point, I don't know why.. ParseOneDetail(): 89 ... ParseOneDetail(): 90 ... ParseOneDetail(): 243 ... ParseOneDetail(): 92 ... ParseOneDetail(): 244 ... ParseOneDetail(): 93 ... ParseOneDetail(): 245 ... ParseOneDetail(): 247 ... ParseOneDetail(): 94 ... ParseOneDetail(): 248 ... ParseOneDetail(): 95 ... ParseOneDetail(): 99 ... ParseOneDetail(): 249 ... ParseOneDetail(): 100 ... _ <hang at this point> Appreciate your help and suggestions to improve this. Thank you! Edit 1: update for method: private void ParseOneDetail(int index) { Console.WriteLine("ParseOneDetail(): " + index + " ... "); ApplicationInfo appInfo = mListAppInfo[index]; var htmlWeb = new HtmlWeb(); var document = htmlWeb.Load(appInfo.AppAnnieURL); // get first one only HtmlNode nodeStoreURL = document.DocumentNode.SelectSingleNode(Constants.XPATH_FIRST); appInfo.StoreURL = nodeStoreURL.Attributes[Constants.HREF].Value; } Edit 2: This is the error output after a while running as Enigmativity suggest, ParseOneDetail(): 234 ... ParseOneDetail(): 87 ... ParseOneDetail(): 235 ... ParseOneDetail(): 236 ... ParseOneDetail(): 88 ... ParseOneDetail(): 238 ... ParseOneDetail(): 89 ... ParseOneDetail(): 90 ... ParseOneDetail(): 239 ... ParseOneDetail(): 92 ... Unhandled Exception: System.AggregateException: One or more errors occurred. --- > System.Net.WebException: The operation has timed out at System.Net.HttpWebRequest.GetResponse() at HtmlAgilityPack.HtmlWeb.Get(Uri uri, String method, String path, HtmlDocum ent doc, IWebProxy proxy, ICredentials creds) in D:\Source\htmlagilitypack.new\T runk\HtmlAgilityPack\HtmlWeb.cs:line 1355 at HtmlAgilityPack.HtmlWeb.LoadUrl(Uri uri, String method, WebProxy proxy, Ne tworkCredential creds) in D:\Source\htmlagilitypack.new\Trunk\HtmlAgilityPack\Ht mlWeb.cs:line 1479 at HtmlAgilityPack.HtmlWeb.Load(String url, String method) in D:\Source\htmla gilitypack.new\Trunk\HtmlAgilityPack\HtmlWeb.cs:line 1103 at HtmlAgilityPack.HtmlWeb.Load(String url) in D:\Source\htmlagilitypack.new\ Trunk\HtmlAgilityPack\HtmlWeb.cs:line 1061 at SimpleChartParser.AppAnnieParser.ParseOneDetail(ApplicationInfo appInfo) i n c:\users\nhn60\documents\visual studio 2010\Projects\FunToolPack\SimpleChartPa rser\AppAnnieParser.cs:line 90 at SimpleChartParser.AppAnnieParser.<ParseDetails>b__0(ApplicationInfo ai) in c:\users\nhn60\documents\visual studio 2010\Projects\FunToolPack\SimpleChartPar ser\AppAnnieParser.cs:line 80 at System.Threading.Tasks.Parallel.<>c__DisplayClass21`2.<ForEachWorker>b__17 (Int32 i) at System.Threading.Tasks.Parallel.<>c__DisplayClassf`1.<ForWorker>b__c() at System.Threading.Tasks.Task.InnerInvoke() at System.Threading.Tasks.Task.InnerInvokeWithArg(Task childTask) at System.Threading.Tasks.Task.<>c__DisplayClass7.<ExecuteSelfReplicating>b__ 6(Object ) --- End of inner exception stack trace --- at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceled Exceptions) at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationTo ken cancellationToken) at System.Threading.Tasks.Parallel.ForWorker[TLocal](Int32 fromInclusive, Int 32 toExclusive, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWit hState, Func`4 bodyWithLocal, Func`1 localInit, Action`1 localFinally) at System.Threading.Tasks.Parallel.ForEachWorker[TSource,TLocal](TSource[] ar ray, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Act ion`3 bodyWithStateAndIndex, Func`4 bodyWithStateAndLocal, Func`5 bodyWithEveryt hing, Func`1 localInit, Action`1 localFinally) at System.Threading.Tasks.Parallel.ForEachWorker[TSource,TLocal](IEnumerable` 1 source, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState , Action`3 bodyWithStateAndIndex, Func`4 bodyWithStateAndLocal, Func`5 bodyWithE verything, Func`1 localInit, Action`1 localFinally) at System.Threading.Tasks.Parallel.ForEach[TSource](IEnumerable`1 source, Act ion`1 body) at SimpleChartParser.AppAnnieParser.ParseDetails() in c:\users\nhn60\document s\visual studio 2010\Projects\FunToolPack\SimpleChartParser\AppAnnieParser.cs:li ne 80 at SimpleChartParser.Program.Main(String[] args) in c:\users\nhn60\documents\ visual studio 2010\Projects\FunToolPack\SimpleChartParser\Program.cs:line 15