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Do I need to use invoke in backgroundworker progresschanged event?

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.IO;
using System.Net;
using System.Xml.Linq;
using System.Diagnostics;
using System.Management;
using System.Runtime.InteropServices;
namespace DownloadFiles
{
public partial class Form1 : Form
{
Stopwatch sw = new Stopwatch();
Stopwatch stopwatch = new Stopwatch();
string filesdirectory = "Downloaded_Files";
string mainurl = "http://www.usgodae.org/ftp/outgoing/fnmoc/models/navgem_0.5/latest_data/";
List<string> parsedlinks = new List<string>();
string path_exe = Path.GetDirectoryName(Application.LocalUserAppDataPath);
List<string> results = new List<string>();
//StreamWriter w = new StreamWriter(#"e:\monitordetector.txt");
public Form1()
{
InitializeComponent();
//DetectScreenName();
label3.Text = "";
label4.Text = "";
label5.Text = "";
label7.Text = "";
button2.Enabled = false;
button3.Enabled = false;
filesdirectory = Path.Combine(path_exe, filesdirectory);
if (!Directory.Exists(filesdirectory))
{
Directory.CreateDirectory(filesdirectory);
}
else
{
if (IsDirectoryEmpty(filesdirectory) == false)
{
button3.Enabled = true;
}
}
}
public bool IsDirectoryEmpty(string path)
{
return !Directory.EnumerateFileSystemEntries(path).Any();
}
private string downloadhtml(string url)
{
backgroundWorker1.ReportProgress(0, "Downloading Main Url");
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
request.Proxy = null;
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
StreamReader sr = new StreamReader(response.GetResponseStream());
string html = sr.ReadToEnd();
sr.Close();
response.Close();
StreamWriter w = new StreamWriter(path_exe + "\\page.html");
w.Write(html);
w.Close();
return html;
}
int Counter = 0;
int percentage = 0;
int total = 0;
int countfiletodownload = 0;
bool processStatus = false;
private void Parseanddownloadfiles()
{
downloadhtml(mainurl);
if (bgw.CancellationPending == false)
{
backgroundWorker1.ReportProgress(0, "Parsing Links");
HtmlAgilityPack.HtmlWeb hw = new HtmlAgilityPack.HtmlWeb();
HtmlAgilityPack.HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();
doc = hw.Load(path_exe + "\\page.html");
foreach (HtmlAgilityPack.HtmlNode link in doc.DocumentNode.SelectNodes("//a[#href]"))
{
string hrefValue = link.GetAttributeValue("href", string.Empty);
if (hrefValue.Contains("US"))
{
string url = "http://www.usgodae.org/ftp/outgoing/fnmoc/models/navgem_0.5/latest_data/" + hrefValue;
parsedlinks.Add(url);
if (bgw.CancellationPending == true)
return;
}
}
countfiletodownload = parsedlinks.Count;
total = parsedlinks.Count;
backgroundWorker1.ReportProgress(0, "Downloading Files");
processStatus = true;
for (int i = 0; i < parsedlinks.Count && bgw.CancellationPending == false; i++)
{
try
{
using (WebClient client = new WebClient())
{
sw.Start();
Uri uri = new Uri(parsedlinks[i]);
string filename = parsedlinks[i].Substring(71);
//client.DownloadFile(parsedlinks[i], filesdirectory + "\\" + filename);
client.DownloadFileAsync(uri, filesdirectory + "\\" + filename);
Counter += 1;
percentage = Counter * 100 / total;
string filenametoreport = filename.Substring(1);
countfiletodownload--;
backgroundWorker1.ReportProgress(percentage, filenametoreport);//countfiletodownload, filenametoreport);
}
}
catch (Exception err)
{
string error = err.ToString();
}
}
}
}
/*void client_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
// Calculate download speed and output it to labelSpeed.
if (label12.InvokeRequired)
{
label12.Invoke(new MethodInvoker(delegate
{
label12.Text = string.Format("{0} kb/s", (e.BytesReceived / 1024d / sw.Elapsed.TotalSeconds).ToString("0.00"));
}));
}
// Update the progressbar percentage only when the value is not the same.
if (progressBar1.InvokeRequired)
{
progressBar1.Invoke(new MethodInvoker(delegate
{
progressBar1.Value = e.ProgressPercentage;
}));
}
// Show the percentage on our label.
if (label13.InvokeRequired)
{
label13.Invoke(new MethodInvoker(delegate
{
label13.Text = e.ProgressPercentage.ToString() + "%";
}));
}
// Update the label with how much data have been downloaded so far and the total size of the file we are currently downloading
if (label14.InvokeRequired)
{
label14.Invoke(new MethodInvoker(delegate
{
label14.Text = string.Format("{0} MB's / {1} MB's",
(e.BytesReceived / 1024d / 1024d).ToString("0.00"),
(e.TotalBytesToReceive / 1024d / 1024d).ToString("0.00"));
}));
}
}*/
/*void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
{
// Reset the stopwatch.
sw.Reset();
if (e.Cancelled == true)
{
MessageBox.Show("Download has been canceled.");
}
else
{
//MessageBox.Show("Download completed!");
}
}*/
private void Form1_Load(object sender, EventArgs e)
{
}
BackgroundWorker bgw;
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
bgw = (BackgroundWorker)sender;
if (bgw.CancellationPending == true)
{
return;
}
else
{
Parseanddownloadfiles();
}
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
if (e.UserState.ToString() == "Downloading Main Url")
{
label3.Text = e.UserState.ToString();
}
if (e.UserState.ToString() == "Parsing Links")
{
label3.Text = e.UserState.ToString();
}
if (e.UserState.ToString() == "Downloading Files")
{
label7.Text = countfiletodownload.ToString();//parsedlinks.Count.ToString();
label3.Text = e.UserState.ToString();
}
if (processStatus == true)
{
if (e.UserState.ToString() != "Downloading Files")
{
label4.Text = e.UserState.ToString();
label7.Text = countfiletodownload.ToString();
progressBar1.Value = e.ProgressPercentage;
/*using (var bitmap = new Bitmap(this.Width, this.Height))
{
this.DrawToBitmap(bitmap, new Rectangle(0, 0, bitmap.Width, bitmap.Height));
bitmap.Save(#"e:\screens\ss.gif" + countscreenshots, System.Drawing.Imaging.ImageFormat.Gif);
countscreenshots += 1;
}*/
}
}
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Error != null)
{
string fff = null;
}
label3.Text = "Operation Cancelled";
button1.Enabled = true;
}
private void button2_Click(object sender, EventArgs e)
{
label3.Text = "Cancelling Operation";
backgroundWorker1.CancelAsync();
button2.Enabled = false;
timer1.Stop();
stopwatch.Stop();
stopwatch.Reset();
}
private void button1_Click(object sender, EventArgs e)
{
label3.Text = "";
label4.Text = "";
label7.Text = "";
backgroundWorker1.RunWorkerAsync();
timer1.Start();
stopwatch.Start();
button1.Enabled = false;
button2.Enabled = true;
}
private void button3_Click(object sender, EventArgs e)
{
Process.Start(filesdirectory);
}
private void timer1_Tick(object sender, EventArgs e)
{
label5.Text = string.Format("{0:hh\\:mm\\:ss}", stopwatch.Elapsed);
}
}
}
for some reason the code inside the event make the whole application to not to be async. If I comment the code not to use it then it's async working fine.
I also want to use the client_DownloadProgressChanged that now is not in use to show and display the downloading infos.
Like speed time using progressBar info per current file download and info for overall progress download.

No*, you do not need to Invoke in a BackgroundWorker's ProgressChanged event. DoWork is run on a background thread but the thread that executes the code inside ProgressChanged (and the other event handlers on a backgroundworker) is done by the thread that created the backgroundworker, which should be the same as the thread that created the other ui controls and hence no Invokation required
*Having said this, pay close attention to the part where I said that BGW will run the ProgressChanged event using the thread that created the BGW. In most cases this will be the UI thread.. if you've used a thread other than the UI thread to create the BGW then YES, invokation would be required. Create the BGW on the UI thread along with all your other controls, if you want a simple life. For the rest of my advice I'll assume this is what you've done.
I wasn't able to understand exactly your problem, but remember that it's the UI thread that runs the event handler. If you send that thread off doing some long task or blocking operation as part of your efforts to update the labels in the UI then it will make the application seem hung. You must let the UI thread complete the code in the event handler as soon as possible. If it will need to access data that is from a long or blocking operation, either have the DoWork calculate the data before it raises its progress, or use another method to avoid blocking the UI thread, like async task pattern
Note that Invoke and blocking the ui are completely different things. Windows controls may only be accessed by the thread they were created with. If another thread wants to access the control, it should use Invoke to cause the ui thread to do the work instead. This is a very different thing to the notion of not jamming up your ui by using the UI thread to read 50 gigabytes from a slow server and not using something that lets it quickly get back to its job of processing window messages and keeping the app responsive

C# BackgroundWorker ProgressChanged doesn't get fired until end of function

I have a method in my class that has some loops inside.
Main purpose of this method is converting some files so I put a progressbar in my form that should get updated after each file has been converted.
I tried every possible combination and I read everything I could but I couldn't solve this issue.
void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
converterProgressBar.Value = e.ProgressPercentage;
}
is called only after the main loop of my method has been executed.
This is my method:
public string Convert()
{
convertBtn.Enabled = false;
bw.WorkerReportsProgress = true;
bw.WorkerSupportsCancellation = true;
bw.DoWork += new DoWorkEventHandler(bw_DoWork);
bw.ProgressChanged += new ProgressChangedEventHandler(bw_ProgressChanged);
bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
totalCount = files.length;
bw.RunWorkerAsync();
if (!Directory.Exists(folder))
{
Directory.CreateDirectory(folder);
}
foreach (string file in files)
{
countFile++;
if (chk.Checked)
{
class1.DoJob();
}
using (// some code))
{
using (//some other code))
{
try
{
using (// again some code)
{
// job executing
}
}
catch (exception
{
}
}
}
convertedVideosL.Text = txtToUpdate;
convertedVideosL.Refresh();
}
countFile = countFile + 1;
MessageBox.Show("Done");
countFile = -1;
return outputFile;
}
And here are the BackgroundWorker Event Handlers:
void bw_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 0; i <= totalCount; i++)
{
if (bw.CancellationPending)
{
e.Cancel = true;
}
else
{
int progress = Convert.ToInt32(i * 100 / totalCount);
(sender as BackgroundWorker).ReportProgress(progress, i);
}
}
}
void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
converterProgressBar.Value = e.ProgressPercentage;
}
void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Cancelled == false)
{
convertedVideosL.Text = "Finished!";
}
else
{
convertedVideosL.Text = "Operation has been cancelled!";
}
}
But I cannot get to update the progress bar for every file that is converted.
It waits for the foreach loop to end and then calls bw_ProgressChanged.
If I put RunWorkerAsync() inside the foreach loop an exception is thrown that says the BackgroundWorker is busy and cannot execute other tasks.
It seems to me obvious that DoWork() only executes a for loop then it shouldn't be aware of the conversion going on but ProgressChanged should be fired by ReportProgress(progress,i).
Could please someone explain me why and help me with a solution?
Thanks!

Currently the conversion is not executed by the instance of the BackgroundWorker type. The conversion should be called from the DoWork event handler.
Please consider extracting the conversion-related functionality:
if (!Directory.Exists(folder))
{
Directory.CreateDirectory(folder);
}
foreach (string file in files)
{
// Details...
}
into the separate method. After that just call the method from the DoWork event handler.
Pseudo-code to demonstrate the idea:
public void StartConversion()
{
...
TWorkerArgument workerArgument = ...;
worker.RunWorkerAsync(workerArgument);
// No message box here because of asynchronous execution (please see below).
}
private void BackgroundWorkerDoWork(object sender, DoWorkEventArgs e)
{
// Get the BackgroundWorker that raised this event.
BackgroundWorker worker = sender as BackgroundWorker;
e.Result = Convert(worker, (TWorkerArgument)e.Argument);
}
private static TWorkerResult Convert(BackgroundWorker worker, TWorkerArgument workerArgument)
{
if (!Directory.Exists(folder))
{
Directory.CreateDirectory(folder);
}
foreach (string file in files)
{
// Details...
worker.ReportProgress(percentComplete);
}
return ...;
}
private void BackgroundWorkerRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
// Show the message box here if required.
}
Please replace the TWorkerArgument and TWorkerResult types appropriately.
Also, please refer to the example which uses the BackgroundWorker class for the additional details: How to: Implement a Form That Uses a Background Operation, MSDN.

Background Worker to populate combobox in windows form application

I want to implement background worker in my windows application.
Currently I am using button event handler to load the combo box with data. As the query hangs the user interface, i would like to implement background worker as that the query runs in different thread. I have never used this background worker in any of my application. I did some research on this and still unable to implement this. Any help or advice will be greatly appreciated.
This is how my button event handler looks like
private void button6_Click(object sender, EventArgs e)
{
if (comboBox1.SelectedItem.ToString() == "All")
{
findAllUser();
}
else
{
//Do Something!!!
}
}
findAllUser() will fetch all the user from active directory which normally takes time and makes the UI unresponsive. Code for findAllUser() looks like this.
public void findAllUser()
{
System.DirectoryServices.DirectoryEntry entry = new System.DirectoryServices.DirectoryEntry("LDAP://DC=xyz, DC=com");
System.DirectoryServices.DirectorySearcher mySearcher = new System.DirectoryServices.DirectorySearcher(entry);
mySearcher.Filter = "(&(objectClass=user))";
foreach (System.DirectoryServices.SearchResult resEnt in mySearcher.FindAll())
{
try
{
System.DirectoryServices.DirectoryEntry de = resEnt.GetDirectoryEntry();
comboBox2.Items.Add(de.Properties["GivenName"].Value.ToString() + " " + de.Properties["sn"].Value.ToString() + " " + "[" + de.Properties["sAMAccountName"].Value.ToString() + "]");
}
catch (Exception)
{
// MessageBox.Show(e.ToString());
}
}
}
Below is how the background worker looks now..all empty
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
}
Any advice how can i implement the code above so that the background worker will populate the combobox2 with the active directory user list.

The easiest way would be to have your findAllUser method build a list of items that need to be added to the combo box, and then have the RunWorkerCompleted method populate the combo box. For example, modify your findAllUser like this:
private List<string> items;
public void findAllUser()
{
items = new List<string>();
System.DirectoryServices.DirectoryEntry entry =
new System.DirectoryServices.DirectoryEntry("LDAP://DC=xyz, DC=com");
System.DirectoryServices.DirectorySearcher mySearcher =
new System.DirectoryServices.DirectorySearcher(entry);
mySearcher.Filter = "(&(objectClass=user))";
foreach (System.DirectoryServices.SearchResult resEnt in mySearcher.FindAll())
{
try
{
System.DirectoryServices.DirectoryEntry de = resEnt.GetDirectoryEntry();
items.Add(de.Properties["GivenName"].Value.ToString() + " " +
de.Properties["sn"].Value.ToString() + " " + "[" +
de.Properties["sAMAccountName"].Value.ToString() + "]");
}
catch (Exception)
{
// MessageBox.Show(e.ToString());
}
}
}
Then, have your DoWork call findAllUser to do the actual work.
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
findAllUser();
}
And finally, have your RunWorkerCompleted populate the combo box:
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
foreach (var item in items)
{
comboBox2.Items.Add(item);
}
}
If you want to show progress, then you need to call ReportProgress from time to time while the worker is doing its business. Since you don't know exactly how long the process will take or exactly how many users it will find, you can't really report accurate progress. In that case, you have to guess. Since you say it takes "like 30 seconds," then you can use that as the 100% mark. So you start a StopWatch when the worker starts its processing, and update every half second or so. Modify your findAllUser function like this:
public void findAllUser()
{
const int ExpectedTime = 30000; // 30,000 milliseconds
// stopwatch keeps track of elapsed time
Stopwatch sw = Stopwatch.StartNew();
// Create a timer that reports progress at 500 ms intervals
System.Timers.Timer UpdateTimer;
UpdateTimer = new System.Threading.Timer(
null,
{
var percentComplete = (100 * sw.ElapsedMilliseconds) / ExpectedTime;
if (percentComplete > 100) percentComplete = 100;
ReportProgress(percentComplete);
// Update again in 500 ms if not already at max
if (percentComplete < 100)
UpdateTimer.Change(500, Timeout.Infinite);
}, 500, Timeout.Infinite);
items = new List<string>();
// rest of findAllUser here
// dispose of the timer.
UpdateTimer.Dispose();
}
And then, in your ProgressChanged event handler, update your progress bar.
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
// Update the progress bar with the value from e.ProgressPercentage
}
Again, because you don't know exactly how long things are going to take, you make an estimate. Above, I estimated 30 seconds, and the code blindly assumes that if 15 seconds have gone by, then it's half done.
Note that I create the timer as a one-shot and re-initialize it after every tick. I do this because I want to prevent concurrent updates. The timer fires on a separate thread, and the ReportProgress method marshals the call to the ProgressChanged event to the UI thread. If the UI thread is busy with other things, then another timer event could come in and you could end up with a bunch of threads all trying to marshal calls to the UI. Probably not a problem in this case because we're only talking a maximum of 60 calls (two calls per second for 30 seconds), but in general it's a good idea to prevent that kind of thing from happening.

Place your code on the backgroundWorker1_DoWork. But I suggest you either use Thread or Task Parallel Library
If you're on .NET 4.0, use the TPL.
You can do it like this:
Task runner = new Task(() =>
{
// do process here
});
runner.Start();
of if you're on older frameworks, use the Thread like this.
Thread thread = new Thread(() =>
{
// do process here
});
thread.IsBackground = true;
thread.Start();
read more about the TPL and Thread.

Using BackgroundWorker is convenient because it automagically invokes the ProgressChanged and RunworkerCompleted event handlers in the UI thread. You can use it like below.
private void AddItem(DirectoryEntry de)
{
comboBox2.Items.Add(de.Properties["GivenName"].Value.ToString() + " " + de.Properties["sn"].Value.ToString() + " " + "[" + de.Properties["sAMAccountName"].Value.ToString() + "]");
}
private void button6_Click(object sender, EventArgs e)
{
if (comboBox1.SelectedItem.ToString() == "All")
{
this.backgroundWorker1.RunWorkerAsync();
}
else
{
//Do Something!!!
}
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
// Bind to the users container.
DirectoryEntry entry = new DirectoryEntry("LDAP://CN=xyz,DC=com");
// Create a DirectorySearcher object.
DirectorySearcher mySearcher = new DirectorySearcher(entry);
try
{
// Create a SearchResultCollection object to hold a collection of SearchResults
// returned by the FindAll method.
SearchResultCollection result = mySearcher.FindAll();
int count = result.Count;
for(int i = 0; i < count; i++)
{
SearchResult resEnt = result[i];
try
{
DirectoryEntry de = resEnt.GetDirectoryEntry();
BeginInvoke(new Action<DirectoryEntry>(AddItem), de);
}
catch (Exception)
{
// MessageBox.Show(e.ToString());
}
this.backgroundWorker1.ReportProgress(i / count);
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
this.progressBar1.Value = e.ProgressPercentage;
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
this.progressBar1.Value = 100;
}

You can use below logic to implement background worker for your code.
var startListenerWorker = new BackgroundWorker();
startListenerWorker.DoWork += new DoWorkEventHandler(this.StartListenerDoWork);
startListenerWorker.RunWorkerAsync();
private void StartListenerDoWork(object sender, DoWorkEventArgs doWorkEventArgs)
{
// Your logic to load comboBox will go here for running your query
}
you can also implement thread to have your logic run on a separate thread.

Creating a multi-thread webdownload via WebClient / BeginInvoke Method

I have actually the following code:
private Stopwatch _sw;
public void DownloadFile(string url, string fileName)
{
string path = #"C:\DL\";
Thread bgThread = new Thread(() =>
{
_sw = new Stopwatch();
_sw.Start();
labelDownloadAudioStatusText.Visibility = Visibility.Visible;
using (WebClient webClient = new WebClient())
{
webClient.DownloadFileCompleted +=
new AsyncCompletedEventHandler(DownloadCompleted);
webClient.DownloadProgressChanged +=
new DownloadProgressChangedEventHandler(DownloadStatusChanged);
webClient.DownloadFileAsync(new Uri(url), path + fileName);
}
});
bgThread.Start();
}
void DownloadStatusChanged(object sender, DownloadProgressChangedEventArgs e)
{
this.BeginInvoke((MethodInvoker) delegate
{
int percent = 0;
if (e.ProgressPercentage != percent)
{
percent = e.ProgressPercentage;
progressBarDownloadAudio.Value = percent;
labelDownloadAudioProgress.Content = percent + "%";
labelDownloadAudioDlRate.Content =
(Convert.ToDouble(e.BytesReceived)/1024/
_sw.Elapsed.TotalSeconds).ToString("0.00") + " kb/s";
Thread.Sleep(50);
}
});
}
private void DownloadCompleted(object sender, AsyncCompletedEventArgs e)
{
this.BeginInvoke((MethodInvoker) delegate
{
labelDownloadAudioDlRate.Content = "0 kb/s";
labelDownloadAudioStatusText.Visibility = Visibility.Hidden;
});
}
My problem is that in a previous version without the outer thread, the whole GUI freezes sporadically and the GUI is liquid when the download is finished. So I googled around and found this: https://stackoverflow.com/a/9459441/2288470
An answer was to pack everything into a separate thread which performs the interaction with DownloadFileAsync, but I got the fault, that the BeginInvoke method can not be found.

When using WPF, the BeginInvoke method is not exposed by the Window class, like it is for Form in WinForms. Instead you should use Dispatcher.BeginInvoke.
Working code:
private Stopwatch _sw;
public void DownloadFile(string url, string fileName)
{
string path = #"C:\DL\";
Thread bgThread = new Thread(() =>
{
_sw = new Stopwatch();
_sw.Start();
labelDownloadAudioStatusText.Visibility = Visibility.Visible;
using (WebClient webClient = new WebClient())
{
webClient.DownloadFileCompleted +=
new AsyncCompletedEventHandler(DownloadCompleted);
webClient.DownloadProgressChanged +=
new DownloadProgressChangedEventHandler(DownloadStatusChanged);
webClient.DownloadFileAsync(new Uri(url), path + fileName);
}
});
bgThread.Start();
}
void DownloadStatusChanged(object sender, DownloadProgressChangedEventArgs e)
{
Dispatcher.BeginInvoke((MethodInvoker) delegate
{
int percent = 0;
if (e.ProgressPercentage != percent)
{
percent = e.ProgressPercentage;
progressBarDownloadAudio.Value = percent;
labelDownloadAudioProgress.Content = percent + "%";
labelDownloadAudioDlRate.Content =
(Convert.ToDouble(e.BytesReceived)/1024/
_sw.Elapsed.TotalSeconds).ToString("0.00") + " kb/s";
Thread.Sleep(50);
}
});
}
private void DownloadCompleted(object sender, AsyncCompletedEventArgs e)
{
Dispatcher.BeginInvoke((MethodInvoker) delegate
{
labelDownloadAudioDlRate.Content = "0 kb/s";
labelDownloadAudioStatusText.Visibility = Visibility.Hidden;
});
}

Invoke method and BeginInvoke method is implemented on System.Windows.Forms.Control Class. If you are not writing code in such as Form Class, you cannot use this method. To resolve this problem, inherit your Job Class from System.Windows.Forms.Control Class, then you could use BeginInvoke method. Please note that you have to create instance on main thread.
public class JobClass : System.Windows.Forms.Control {
.....
}

cross-thread calls?

This is mt first time trying to write a not web based program, and my first time writing anything in C#.
I need a program that monitors folders, but I can't get it to work.
I have used the example from this post Using FileSystemWatcher with multiple files but is trying to make it a form.
My current problem comes in the ProcessQueue function where fileList apparently is defined in another thread.
Whenever a file is actually submitted to the watched folder I get an error that using fileList is a cross thread call
Can anyone explain this error to me, and how to fix it?
namespace matasWatch
{
public partial class Form1 : Form
{
private int n = 1;
private bool isWatching = false;
private List<string> filePaths;
private System.Timers.Timer processTimer;
private string watchedPath;
private FileSystemWatcher watcher;
public Form1()
{
filePaths = new List<string>();
watchedPath = "C:\\Users\\username\\Desktop\\test";
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
if (!isWatching)
{
button1.Text = "Stop";
isWatching = true;
watcher = new FileSystemWatcher();
watcher.Filter = "*.*";
watcher.Created += Watcher_FileCreated;
watcher.Error += Watcher_Error;
watcher.Path = watchedPath;
watcher.IncludeSubdirectories = true;
watcher.EnableRaisingEvents = true;
}
else {
button1.Text = "Watch";
isWatching = false;
watcher.EnableRaisingEvents = false;
watcher.Dispose();
watcher = null;
}
}
private void Watcher_Error(object sender, ErrorEventArgs e)
{
// Watcher crashed. Re-init.
isWatching = false;
button1_Click(sender, e);
}
private void Watcher_FileCreated(object sender, FileSystemEventArgs e)
{
filePaths.Add(e.FullPath);
if (processTimer == null)
{
// First file, start timer.
processTimer = new System.Timers.Timer(2000);
processTimer.Elapsed += ProcessQueue;
processTimer.Start();
}
else{
// Subsequent file, reset timer.
processTimer.Stop();
processTimer.Start();
}
}
private void ProcessQueue(object sender, ElapsedEventArgs args)
{
try
{
fileList.BeginUpdate();
foreach (string filePath in filePaths)
{
fileList.Items.Add("Blaa");
}
fileList.EndUpdate();
filePaths.Clear();
}
finally
{
if (processTimer != null)
{
processTimer.Stop();
processTimer.Dispose();
processTimer = null;
}
}
}
}
}

I assume that fileList is a windows forms control. The ProcessQueue method is called from a timer thread which is by default a background thread. The fileList control resides in the UI thread. You need to use the Invoke() method of the form passing it in a delegate the updates the fileList control.
Invoke(new Action(() =>
{
fileList.BeginUpdate();
foreach (string filePath in filePaths)
{
fileList.Items.Add("Blaa");
}
fileList.EndUpdate();
filePaths.Clear();
}));

Try using System.Windows.Forms.Timer instead of System.Timers.Timer so the timer tick event is executed on the UI thread.
See here for more details.