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The calling thread cannot access this object, because another thread owns it

I am using BackgroundWorker for my WPF application, but what is in the Worker_RunDetection function does not work and there is no interface update from Worker_ProgressShow. Worker_ProgressShow is for updating interface and Worker_RunDetection processes images from path I got from user. This application must search for text in images and tell user how many images have already been processed. What`s wrong?
UPD: I used RunWorkerCompleted and got
The calling thread cannot access this object, because another thread owns it.
Not I use Dispatcher.Invoke, but interface freeze. Progress is a component (ProgressBar).
int numberProcessed = 0;
private void MainForm_ContentRendered(object sender, EventArgs e)
{
worker = new BackgroundWorker();
worker.WorkerReportsProgress = true;
worker.DoWork += Worker_RunDetection;
worker.ProgressChanged += Worker_ProgressShow;
}
private void Worker_ProgressShow(object sender, ProgressChangedEventArgs e)
{
this.Dispatcher.Invoke(() => {
Progress.Value = Convert.ToInt32(e.UserState);
if (Progress.Value % 10 == 0)
LogTextBox.Text += $"\n{Progress.Value} images are processed";
});
}
private void Worker_RunDetection(object sender, DoWorkEventArgs e)
{
this.Dispatcher.Invoke(() => {
foreach (String imageFileName in Directory.GetFiles(PathTextBox.Text))
{
detector = new ImageProcessing(isFolder, imageFileName, pathFolder);
detector.DetectTextOnImage();
numberProcessed++;
(sender as BackgroundWorker).ReportProgress(numberProcessed);
}
});
}
private void StartButton_Click(object sender, RoutedEventArgs e)
{
if (PathTextBox.Text != "")
{
worker.RunWorkerAsync();
}
}

Problem was with the Apth taken from PathTextBox.Text.
It must not reference Controls declared in the UI Thread in the DoWork() handler of a BackGroundWorker.
Everything works fine if the task logic is separated from the UI.
Corrected code:
int numberProcessed = 0;
private void MainForm_ContentRendered(object sender, EventArgs e)
{
worker = new BackgroundWorker();
worker.WorkerReportsProgress = true;
worker.DoWork += Worker_RunDetection;
worker.ProgressChanged += Worker_ProgressShow;
}
private void Worker_ProgressShow(object sender, ProgressChangedEventArgs e)
{
Progress.Value = Convert.ToInt32(numberProcessed);
if (Progress.Value % 10 == 0)
LogTextBox.Text += $"\n{Progress.Value} images are processed";
}
private void Worker_RunDetection(object sender, DoWorkEventArgs e)
{
foreach (String imageFileName in Directory.GetFiles(e.Argument.ToString()))
{
detector = new ImageProcessing(isFolder, imageFileName, pathFolder);
detector.DetectTextOnImage();
numberProcessed++;
(sender as BackgroundWorker).ReportProgress(numberProcessed);
}
}

Why WinForm Gets Stuck with BackgroundWorker?

hi guys i tried to copy some files with this Code everything is good and the app will copy files but in copy progress i cant move my app or do anything
i tried to use thread but its not works i also use backgroundWorker but still nothing the only control that doesnt get stuck is progressBar its works fine here is my code :
public Form1()
{
InitializeComponent();
backgroundWorker1.Dispose();
backgroundWorker1.DoWork += BackgroundWorker_DoWork;
backgroundWorker1.RunWorkerCompleted += BackgroundWorker_RunWorkerCompleted;
backgroundWorker1.ProgressChanged += BackgroundWorker_ProgressChanged;
backgroundWorker1.WorkerReportsProgress = true;
backgroundWorker2.DoWork += BackgroundWorker2_DoWork;
backgroundWorker2.WorkerReportsProgress = true;
}
private void BackgroundWorker2_DoWork(object sender, DoWorkEventArgs e)
{
File.Copy(sourcePath, targetPath);
}
private void BackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 0; i < fileSize; i++)
{
int p = (i + 1) * 100 / Convert.ToInt32(fileSize);
backgroundWorker1.ReportProgress(p);
}
}
private void BackgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
}
private void BackgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
lbProgress.Text = e.ProgressPercentage.ToString();
progressBar1.Value = e.ProgressPercentage;
}
private void btnTarget_Click(object sender, EventArgs e)
{
folderBrowser = new FolderBrowserDialog();
if (folderBrowser.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
targetPath += folderBrowser.SelectedPath + #"\" + fileName;
lbTarget.Text = targetPath;
}
}
private void btnSource_Click(object sender, EventArgs e)
{
op = new OpenFileDialog();
if (op.ShowDialog() == DialogResult.OK)
{
sourcePath += op.FileName;
lbSource.Text = sourcePath;
fileInfo = new FileInfo(sourcePath);
fileSize = fileInfo.Length / 1024;
fileName = fileInfo.Name;
MessageBox.Show(string.Format("File size is: {0} KB", fileSize));
}
}
private void btnCopy_Click(object sender, EventArgs e)
{
backgroundWorker1.RunWorkerAsync();
backgroundWorker2.RunWorkerAsync();
}

You're updating the progress bar faster than the UI can update, for every single byte of the file being copied in a tight loop. You're flooding the UI thread with pointless work.
Remove backgroundWorker1, it's not doing anything useful anyway. If you don't have a way to track the progress (which you don't with File.Copy), just use a progress bar without progress (set Style to Marquee).

For testing I created a simple winform application with a button, a label and a background worker and added the following corresponding events:
private void OnBackgroundWorkerDoWork(object sender, DoWorkEventArgs e)
{
var worker = (BackgroundWorker)sender;
for (int i = 0; i < 10; i++)
{
Thread.Sleep(500);
worker.ReportProgress(i * 10);
}
}
private void OnBackgroundWorkerProgressChanged(object sender, ProgressChangedEventArgs e)
{
labelProgress.Text = e.ProgressPercentage.ToString();
}
private void OnBackgroundWorkerRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
labelProgress.Text = "Done";
}
private void OnButtonProgressClick(object sender, System.EventArgs e)
{
backgroundWorker.RunWorkerAsync();
}
Works as expected.

Could You try to update Your DoWork to this:
private void BackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
int mainProgress = 0;
for (int i = 0; i < fileSize; i++)
{
int calculatedProgress = (i + 1) * 100 / Convert.ToInt32(fileSize);
if(calculatedProgress > mainProgress)
{
mainProgress = calculatedProgress;
backgroundWorker1.ReportProgress(mainProgress);
}
}
}
maybe You are doing so many updates that simply Window Thread is all the time updating only progress and don't have a time to make anything else?

Updating progressbar through backgroundworker in method

My programm (in C# using Windows Forms) is reading and parsing large amounts of Data and I'm using a Backgroundworker which calls those global methods (reading and parsing). I'd like to keep the user updated on how long it's going to take, so the Backgroundworker is supposed to display what action its doing and has a progressbar that should fill for every individual action too.
Unfortunately, I can't get it to work, as the progressbar just doesn't update at all and just stays empty.
Here is what I have so far:
private void InitializeBackgroundWorker()
{
backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork);
backgroundWorker1.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted);
backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
}
private void buttonParse_Click(object sender, EventArgs e)
{
DescriptionLabel.Visible = true;
progressBar1.Visible = true;
backgroundWorker1.RunWorkerAsync();
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar1.Value = e.ProgressPercentage;
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = sender as BackgroundWorker;
Methods.ParsePerfusionData(backgroundWorker1); //Also tried using 'worker' here, but didnt work either
}
And in the method it looks like that:
public static void ParsePerfusionData(BackgroundWorker worker)
{
for (int i = 2; i < Globals.DataList.Count; i++)
{
worker.ReportProgress(i / amount * 100);
rest of the code etc.
}
}
Can I not use a backgroundworker in a global method like that? Thanks in advance!

When i < amount then i / amount * 100 = 0 * 100 = 0.
Simply use i * 100 / amount instead.
Also make sure backgroundWorker1.WorkerReportsProgress = true

You can only report progress between distinct operations. That means either:
using a very modern class that supports this level of reporting. Such a classs might not exist for your case.
reverse engineering parts of the code down to the loop you want to make reporting on. Usually the loop that itterates over files or the like.
GUI updates must be contained to RunWorkerCompelted and ProgressReport events. And depending on how often updates happen, ProgressReport may have to be kept to only updating a progress bar.
Here some old code I wrote with BackgroundWorker wich should get you started:
#region Primenumbers
private void btnPrimStart_Click(object sender, EventArgs e)
{
if (!bgwPrim.IsBusy)
{
//Prepare ProgressBar and Textbox
int temp = (int)nudPrim.Value;
pgbPrim.Maximum = temp;
tbPrim.Text = "";
//Start processing
bgwPrim.RunWorkerAsync(temp);
}
}
private void btnPrimCancel_Click(object sender, EventArgs e)
{
if (bgwPrim.IsBusy)
{
bgwPrim.CancelAsync();
}
}
private void bgwPrim_DoWork(object sender, DoWorkEventArgs e)
{
int highestToCheck = (int)e.Argument;
//Get a reference to the BackgroundWorker running this code
//for Progress Updates and Cancelation checking
BackgroundWorker thisWorker = (BackgroundWorker)sender;
//Create the list that stores the results and is returned by DoWork
List<int> Primes = new List<int>();
//Check all uneven numbers between 1 and whatever the user choose as upper limit
for(int PrimeCandidate=1; PrimeCandidate < highestToCheck; PrimeCandidate+=2)
{
//Report progress
thisWorker.ReportProgress(PrimeCandidate);
bool isNoPrime = false;
//Check if the Cancelation was requested during the last loop
if (thisWorker.CancellationPending)
{
//Tell the Backgroundworker you are canceling and exit the for-loop
e.Cancel = true;
break;
}
//Determin if this is a Prime Number
for (int j = 3; j < PrimeCandidate && !isNoPrime; j += 2)
{
if (PrimeCandidate % j == 0)
isNoPrime = true;
}
if (!isNoPrime)
Primes.Add(PrimeCandidate);
}
//Tell the progress bar you are finished
thisWorker.ReportProgress(highestToCheck);
//Save Return Value
e.Result = Primes.ToArray();
}
private void bgwPrim_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
pgbPrim.Value = e.ProgressPercentage;
}
private void bgwPrim_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
pgbPrim.Value = pgbPrim.Maximum;
this.Refresh();
if (!e.Cancelled && e.Error == null)
{
//Show the Result
int[] Primes = (int[])e.Result;
StringBuilder sbOutput = new StringBuilder();
foreach (int Prim in Primes)
{
sbOutput.Append(Prim.ToString() + Environment.NewLine);
}
tbPrim.Text = sbOutput.ToString();
}
else
{
tbPrim.Text = "Operation canceled by user or Exception";
}
}
#endregion

Running a progress bar using Background Controller in c#

I don't have a thorough knowledge about controlling threads in c#. I want to create a progress bar while running a method.
I have two forms:
Form1 is the form which show up as you run the app. It has a button called btnScrape. When it is clicked the method should be called, the form with the progress bar should show up. Form1 should be disabled to the user until the progress bar is completed.
ProgressBarForm - this has the progress bar and a label.
The code is as follows.
//In Form1.cs I have a button.
private void btnScrape_Click(object sender, EventArgs e)
{
//gather data for folloeing parameters from the form.
Controller cntrlr = new Controller(urlFilePath, destinationPath, destinationfilename,cmbDepth.SelectedIndex);
cntrlr.Vmain(); // this is the method in controller class. while this is running i want show the progress bar.
}
// in Contrller class
class Controller{
List<string> urlList = null;
URLFileReader urlFileReader = null;
HTTPWorker httpWorker = null;
SourceReader srcreader = null;
ReportWriter reportWriter = null;
string urlFilePath, destinationPath, destinationFileName;
int depth;
public Controller(string urlFilePath,string destinationPath,string destinationFileName,int depth)
{
this.urlFilePath = urlFilePath;
this.destinationPath = destinationPath;
this.destinationFileName = destinationFileName;
this.urlList = new List<string>();
this.urlFileReader = new URLFileReader();
this.httpWorker = new HTTPWorker(this.destinationPath);
this.reportWriter = new ReportWriter(this.destinationPath,this.destinationFileName);
this.srcreader = new SourceReader(this.reportWriter);
this.depth = depth;
}
//this is the method
public void Vmain(){
this.urlFileReader.ReadURL(urlFilePath);
this.urlList = urlFileReader.geturlList();
string pageSrc;
foreach (string requestUrl in urlList)
{
//do sruff for requestUrl
//the progressbar should move as the urlList iterate.
//additionally i want the label on the top of progress bar to display the current "requestUrl"
//as the urlList is over i want quit from the progressbar window and come back to Form1. Till the progrss bar is completed Form1 should be disabled for the user.
}
}
}
Please explain what is happening there and give a working code if you can. Thank you in advance. There were not any perfect answer that worked for me, even though I spent two days for this. I tried with BackgroundWorkerand threads. But no solution found. :(

In the main form you could use this code:
private Progressfrm _loadForm;
private void ShowProgress()
{
ToggleForm();
_loadForm = new Progressfrm();
_loadForm.ShowDialog();
var tcheck = new Thread(CheckLoadedProgress);
tcheck.Start();
//do stuff here
}
private void CheckLoadedProgress()
{
while (_loadForm.IsAccessible) { }
ToggleForm();
}
private void ToggleForm()
{
Invoke(new Action(() => Enabled = !Enabled));
}
private void btnScrape_Click(object sender, EventArgs e)
{
var tform = new Thread(ShowProgress);
tform.Start();
}
Then the Progress-Form will appear until it is filled:
private ProgressBar _progressBar;
private void Progressfrm_Shown(object sender, EventArgs e)
{
_progressBar = new ProgressBar { Size = new Size(100, 20), Location = new Point(10, 10) };
Controls.Add(_progressBar);
_progressBar.Show();
Refresh();
LoadProgress();
}
private void LoadProgress()
{
while (_progressBar.Value < 100)
{
_progressBar.Value++;
Thread.Sleep(100);
}
Close();
}
On this Form you have to add the Event Shown and add the code like in my example. Hope this helps.

Use BackgroundWorker class to output progressBar and statusLabel changes:
BackgroundWorker bgw;
private void btnScrape_Click(object sender, EventArgs e)
{
bgw = new BackgroundWorker();
bgw.WorkerReportsProgress = true;
bgw.DoWork += new DoWorkEventHandler(bgw_DoWork);
bgw.ProgressChanged += new ProgressChangedEventHandler(bgw_ProgressChanged);
bgw.RunWorkerAsync();
}
void bgw_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 1; i <= 100; i++)
{
Thread.Sleep(100);
bgw.ReportProgress(i);
}
}
private void bgw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar1.Value = e.ProgressPercentage;
}
This is only an example how to update controls in an asynchron way.

Background Worker Issue

Edit: I solved the problem by creating the background worker by creating it in code instead of dragging and dropping in design.
Now I know how to use a background worker.
Question
It's my first time using a BGWorker, so here's my issue...
The cursor doesn't change to "Wait".
The progress bar doesn't update.
RunWorkerCompleted isn't invoked.
But the textbox does update.
Am I doing something wrong ?
The Code
using System;
using System.ComponentModel;
using System.Windows.Forms;
namespace BGWorker
{
public partial class Main : Form
{
public Main()
{
InitializeComponent();
progressBar1.Minimum = 0;
progressBar1.Value = 0;
progressBar1.Maximum = 100;
}
private void button1_Click(object sender, EventArgs e)
{
Cursor.Current = Cursors.WaitCursor;
backgroundWorker1.RunWorkerAsync();
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 1; i <= 100; i++)
{
textBox1.AppendText(i.ToString());
textBox1.AppendText("\n");
backgroundWorker1.ReportProgress(i);
}
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar1.Value = e.ProgressPercentage;
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Error != null)
{
label1.Text = e.Error.Message;
}
else
{
label1.Text = "All Done !";
Cursor.Current = Cursors.Default;
}
}
}
}
Thanks.

I agree with pst.
Always create your worker in the code behind - dragging and dropping on the form is never a good idea
You never access UI elements from the DoWork. You can only do this from the ReportProgress and RunWorker Completed Events
Your if statement segment should contain your most common path with the least common path in the else.
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
StringBuilder sb = new StringBuilder();
for (int i = 1; i <= 100; i++)
{
sb.AppendLine(i.ToString());
backgroundWorker1.ReportProgress(i);
}
e.Result = sb.ToString();
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Error == null)
{
textbox1.Text = e.Result.ToString();
label1.Text = "All Done !";
Cursor.Current = Cursors.Default;
}
else
{
label1.Text = e.Error.Message;
}
}