Parallel.ForEach
keeps on running and my program does not end. I am unable to trace where it goes after the first iteration. My guess is that gets a deadlock and keeps on doing context switching.
private void ReadInputFile()
{
var collection = new ConcurrentBag<PropertyRecord>();
var lines = System.IO.File.ReadLines(InputFileName);
int i = 0;
int RecordsCount = lines.Count();
Parallel.ForEach(lines, line =>
{
if (string.IsNullOrWhiteSpace(line))
{
return;
}
var tokens = line.Split(',');
var postalCode = tokens[0];
var country = tokens.Length > 1 ? tokens[1] : "england";
SetLabelNotifyTwoText(
string.Format(
"Reading PostCode {0} out of {1}"
i,
lines.Length));
var tempRecord = GetAllAddesses(postalCode, country);
if (tempRecord != null)
{
foreach (PropertyRecord r in tempRecord)
{
collection.Add(r);
}
}
});
}
private List<PropertyRecord> GetAllAddesses(
string postalCode,
string country = "england")
{
SetLabelNotifyText("");
progressBar1.Value = 0;
progressBar1.Update();
var records = new List<PropertyRecord>();
using (WebClient w = new WebClient())
{
var url = CreateUrl(postalCode, country);
var document = w.DownloadString(url);
var pagesCount = GetPagesCount(document);
if (pagesCount == null)
{
return null;
}
for (int i = 0; i < pagesCount; i++)
{
SetLabelNotifyText(
string.Format(
"Reading Page {0} out of {1}",
i,
pagesCount - 1));
url = CreateUrl(postalcode,country, i);
document = w.DownloadString(url);
var collection = Regex.Matches(
document,
"<div class=\"soldDetails\">(.|\\n|\\r)*?class=" +
"\"soldAddress\".*?>(?<address>.*?)(</a>|</div>)" +
"(.|\\n|\\r)*?class=\\\"noBed\\\">(?<noBed>.*?)" +
"</td>|</tbody>");
foreach (var match in collection)
{
var r = new PropertyRecord();
var bedroomCount = match.Groups["noBed"].Value;
if(!string.IsNullOrEmpty(bedroomCount))
{
r.BedroomCount = bedroomCount;
}
else
{
r.BedroomCount = "-1";
}
r.address = match.Groups["address"].Value;
var line = string.Format(
"\"{0}\",{1}",
r.address
r.BedroomCount);
OutputLines.Add(line);
Records.Add(r);
}
}
}
return Records;
}
It runs fine without Parallel.ForEach
, but using Parallel.ForEach
is in requirements.
I have debugged it and after returning from GetAllAdresses
-method first time, Step Next button halts and it just keep on debugging in the background. It doesn't come back on any bookmark I have placed.
As you said in comments, your SetLabelNotifyText
and SetLabelNotifyTwoText
methods calls Control.Invoke
.
For Control.Invoke
to work, Main thread has to be free, but in your case you seem to block the main thread by invoking Parallel.ForEach
in it.
Here is a minimal reproduction:
private void button1_Click(object sender, EventArgs e)
{
Parallel.ForEach(Enumerable.Range(1, 100), (i) =>
{
Thread.Sleep(10);//Simulate some work
this.Invoke(new Action(() => SetText(i)));
});
}
private void SetText(int i)
{
textBox1.Text = i.ToString();
}
Main thread waits for Parallel.ForEach
and worker threads waits for Main thread, and thus results in deadlock.
How to fix: Don't use Invoke
simply use BeginInvoke
or don't block the MainThread.
If this isn't the case post sscce, that will be helpful for us