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C# code refactoring Background worker

On .NET Windows form, I have Background worker component that works fine. I have 5 forms, that has basically same Background worker on it with same code.
Can I extract this code to other class and somehow use it, considering this is an event? This is code I have on form. It takes 20 lines of code, and it would be nice if this can be refactored. Note: as you can see, I have already put it to other class BackgroundWorkerHelper, but can I also somehow refactor this events on Background worker, so that it is in other class as well, this way code is less and reused.
private void RunBackgroundWorker(string infoLabelText, int imageIndex)
{
BackgroundWorkerHelper.Run(backgroundWorker, progressBar, infoLabelText, imageIndex);
}
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorkerHelper.DoWork(backgroundWorker);
}
private void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
BackgroundWorkerHelper.ProgressChanged(sender, e, progressBar);
}
private void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
BackgroundWorkerHelper.RunWorkerCompleted(sender, e, progressBar);
}
Note: for now I would like to avoid using user control. I know I could do it, but then you have code that handles placing user control and so on. I am still not very good in it.

Here is solution, thanks to rory who gave me idea how to do it. First, I made this class:
public class BackgroundWorkerHelper
{
private static string _infoLabelText = string.Empty;
public BackgroundWorker _BackgroundWorker;
private BarEditItem _marqueeInfo;//this is marquee progress bar
public BackgroundWorkerHelper(BarEditItem marqueeInfo)
{
_marqueeInfo = marqueeInfo;
_BackgroundWorker = new BackgroundWorker();
_BackgroundWorker.WorkerReportsProgress = true;
_BackgroundWorker.WorkerSupportsCancellation = true;
_BackgroundWorker.DoWork += backgroundWorker_DoWork;
_BackgroundWorker.ProgressChanged += backgroundWorker_ProgressChanged;
_BackgroundWorker.RunWorkerCompleted += backgroundWorker_RunWorkerCompleted;
}
public void Run(string labelText, int imageIndex)
{
_marqueeInfo.Caption = labelText;
_marqueeInfo.ImageIndex = imageIndex;
if (!_BackgroundWorker.IsBusy)
_BackgroundWorker.RunWorkerAsync();
else
_marqueeInfo.Caption = "Busy processing saving data, please wait...";
}
public void DoWork()
{
for (int i = 0; i <= 5; i++)
{
_BackgroundWorker.ReportProgress(i); // call backgroundWorker_ProgressChanged event and pass i (which is e argument e.ProgressPercentage) to update UI controls
Thread.Sleep(250);
}
}
public void ProgressChanged(object sender, ProgressChangedEventArgs e)
{
_marqueeInfo.Visibility = BarItemVisibility.Always;
}
public void RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
_marqueeInfo.Visibility = BarItemVisibility.Never;
}
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
DoWork();
}
private void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
ProgressChanged(sender, e);
}
private void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
RunWorkerCompleted(sender, e);
}
then in FORM, in class level above constructor place
private readonly BackgroundWorkerHelper _backgroundWorkerHelper;
then in Form Constructor instantiate class
_backgroundWorkerHelper = new BackgroundWorkerHelper(marqueeInfo);
and then I just call it in my form
_backgroundWorkerHelper.Run("Saving", 14);

Show busy loader while executing action

I have modified Background worker private AbortableBackgroundWorker _worker;
public class AbortableBackgroundWorker : BackgroundWorker
{
//Internal Thread
private Thread _workerThread;
protected override void OnDoWork(DoWorkEventArgs e)
{
try
{
base.OnDoWork(e);
}
catch (ThreadAbortException)
{
e.Cancel = true; //We must set Cancel property to true!
Thread.ResetAbort(); //Prevents ThreadAbortException propagation
}
}
public void Abort()
{
if (_workerThread != null)
{
_workerThread.Abort();
_workerThread = null;
}
}
}
And have method which init BgWorker
private void BusyLoader(Action doWorkAction)
{
if (_worker == null)
{
_worker = new AbortableBackgroundWorker();
_worker.WorkerReportsProgress = true;
_worker.WorkerSupportsCancellation = true;
_worker.DoWork += (sender, e) => _worker_DoWork(sender, e, doWorkAction);
_worker.RunWorkerCompleted += _worker_RunWorkerCompleted;
}
if (!_worker.IsBusy)
_worker.RunWorkerAsync();
}
private void _worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
loadingPanel.StopSpin();
_worker.Abort();
_worker.Dispose();
}
private void _worker_DoWork(object sender, DoWorkEventArgs e, Action action)
{
loadingPanel.StartSpin();
this.Dispatcher.Invoke(action);
}
When I call method BusyLoader I want to pass there Action, which should be executed and at this time busy Indicator should be shown.
I have tried It. And it seems to work but only for first call of BusyLoader. Because _worker.DoWork has the same method, as I understand.
How can I manage to change _worker.DoWork method for every new call of BusyLoader ? Or it is bad approach to pass Action like that?

You said it helped so will post comment as an answer
_worker is not null on the second call so _worker_DoWork is not redefined. Try removing and adding.

NullReferenceException happens when sending message back to message dialog from BackGroundWorker

It's a C# winform .Net framework 2.0 project: The time-consuming network transferring jobs run in a BackupgroundWorker. In this backgroundwork thread, SynchronizationContext method is used to send the current job title to a message dialog in the main UI thread. However, in my code, thread racing problem happens and "NullReferenceException" is given sometime (not always, but randomly). Here is my code:
private void DoBtn_Click(object sender, EventArgs e)
{
m_msgForm = new MsgForm(); //m_msgForm is a member variable of the class, and MsgForm is a form class with a "public static SynchronizationContext synContext"
m_msgForm.UpdateMsg("starting ..."); //UpdateMsg is public method to show progress information
BackgroundWorker myBackgroundWorker = new BackgroundWorker();
myBackgroundWorker.DoWork +=new DoWorkEventHandler(myBackgroundWorker_DoWork);
myBackgroundWorker.RunWorkerCompleted +=new RunWorkerCompletedEventHandler(myBackgroundWorker_RunWorkerCompleted);
myBackgroundWorker.RunWorkerAsync(theBackgroundArgument);
m_msgForm.ShowDialog(); //show as a modal dialog
}
And in the Background worker thread:
private void myBackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
//... some code
string msgText ="doing job: " +job.Title;
RestoreMsgForm.synContext.Send(m_msgForm.UpdateMsg, msgText); //send message to m_msgForm in the UI thread
//... some code
}
The problem is : sometime the "RestoreMsgForm.synContext.Send() in the backgroundworker thread will run before m_msgForm.ShowDialog() in the UI thead.
And in this case, NullReferenceException will be throw.
How to solve this problem? thanks.
the definition of RestoreMsgForm is
public partial class RestoreMsgForm : Form
{
public static SynchronizationContext synContext;
public RestoreMsgForm()
{
InitializeComponent();
}
private void RestoreMsgForm_Load(object sender, EventArgs e)
{
synContext = SynchronizationContext.Current;
}
public void UpdateMsg(object msg)
{
msgLabel.Text = (string)msg;
}
}

See if it works like this instead:
private void DoBtn_Click(object sender, EventArgs e)
{
m_msgForm = new MsgForm(); //m_msgForm is a member variable of the class, and MsgForm is a form class with a "public static SynchronizationContext synContext"
m_msgForm.UpdateMsg("starting ..."); //UpdateMsg is public method to show progress information
BackgroundWorker myBackgroundWorker = new BackgroundWorker();
myBackgroundWorker.DoWork += new DoWorkEventHandler(myBackgroundWorker_DoWork);
myBackgroundWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(myBackgroundWorker_RunWorkerCompleted);
myBackgroundWorker.WorkerReportsProgress = true;
myBackgroundWorker.ProgressChanged += new ProgressChangedEventHandler(myBackgroundWorker_ProgressChanged);
myBackgroundWorker.RunWorkerAsync(theBackgroundArgument);
}
private void myBackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = (BackgroundWorker)sender;
worker.ReportProgress(-1);
//... some code
string msgText = "doing job: " + job.Title;
worker.ReportProgress(0, msgText);
//... some code
worker.ReportProgress(0, "...other text...");
//... some code
worker.ReportProgress(0, "...etc...");
}
void myBackgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
if (e.ProgressPercentage == -1)
{
m_msgForm.ShowDialog(); //show as a modal dialog
}
else
{
m_msgForm.UpdateMsg(e.UserState.ToString);
}
}
*Note that we have to set .WorkerReportsProgress = true for the BackgroundWorker() so we can use ReportProgress() and receive the ProgressChanged() event.

updating gui from another class c#

hey i am new to c# plz help.
i am writing a program that sorts data in a file and it is a time consuming process so i thought that i should run it in a separate thread and since it has alot of step so i made a new class for it. the problem is that i want to show the progress in the main GUI and i know for that i have to use Invoke function but the problem is that the form control variables are not accessible it this class. what should i do ??????
sample code:
public class Sorter
{
private string _path;
public Sorter(string path)
{
_path = path;
}
public void StartSort()
{
try
{
processFiles(_path, "h4x0r"); // Just kidding
}
catch (Exception e)
{
MessageBox.Show("Error: " + e.ToString(), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
private void processFiles(string Dir, string[] key)
{
/* sorting program */
}
and it is used as
public partial class Form1 : Form
{
Sorter sort;
public Form1()
{
InitializeComponent();
}
private void browseBtn_Click(object sender, EventArgs e)
{
if (folderBrowserDialog1.ShowDialog() == DialogResult.OK)
textBox1.Text = folderBrowserDialog1.SelectedPath;
}
private void startBtn_Click(object sender, EventArgs e)
{
if (startBtn.Text == "Start Sorting")
{
Thread worker = new Thread(new ThreadStart(delegate() {
sort = new Sorter(textBox1.Text);
sort.StartSort(); }));
worker.start();
}
else
MessageBox.Show("Cancel");//TODO: add cancelling code here
}
}
plz help..

Add an Event to your class that is doing the multi-threaded work, that triggers when the progress changes. Have your form subscribe to this event and update the progress bar.
Note ProgressEventArgs is a little class that inherits EventArgs and has an Integer for the progress.
// delegate to update progress
public delegate void ProgressChangedEventHandler(Object sender, ProgressEventArgs e);
// Event added to your worker class.
public event ProgressChangedEventHandler ProgressUpdateEvent
// Method to raise the event
public void UpdateProgress(object sender, ProgressEventArgs e)
{
ProgressChangedEventHandler handler;
lock (progressUpdateEventLock)
{
handler = progressUpdateEvent;
}
if (handler != null)
handler(sender, e);
}

I would recommend you read up on the BackgroundWorker class. It is exactly for the problem you are trying to solve and makes things a lot easier than doing manual threading yourself.
Brief Example
public Form1()
{
InitializeComponent();
backgroundWorker.WorkerReportsProgress = true;
backgroundWorker.WorkerSupportsCancellation = true;
backgroundWorker.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker_ProgressChanged);
}
void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar1.Value = e.ProgressPercentage;
}
private void btnStart_Click(object sender, EventArgs e)
{
if (!backgroundWorker.IsBusy)
backgroundWorker.RunWorkerAsync();
}
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 1; i < 101; ++i)
{
if (backgroundWorker.CancellationPending)
{
e.Cancel = true;
break;
}
else
{
//Sort Logic is in here.
Thread.Sleep(250);
backgroundWorker.ReportProgress(i);
}
}
}
private void btnCancel_Click(object sender, EventArgs e)
{
if (backgroundWorker.IsBusy && backgroundWorker.WorkerSupportsCancellation)
backgroundWorker.CancelAsync();
}

You could do something like this:
public delegate void StatusReporter(double progressPercentage);
public class MainClass
{
public void MainMethod()
{
Worker worker = new Worker(ReportProgress);
ThreadStart start = worker.DoWork;
Thread workThread = new Thread(start);
workThread.Start();
}
private void ReportProgress(double progressPercentage)
{
//Report here!!!
}
}
public class Worker
{
private readonly StatusReporter _reportProgress;
public Worker(StatusReporter reportProgress)
{
_reportProgress = reportProgress;
}
public void DoWork()
{
for (int i = 0; i < 100; i++ )
{
// WORK, WORK, WORK
_reportProgress(i);
}
}
}

There are a few option available to solve this sort of issue. In any case, you will have to fiddle with Invoke to get the UI to update.
You could...
...add an event that fires on your new class which your UI can listen to, and Invoke as applicable - you'd still need to pass the data to your worker class (by constructor, properties, method call, etc)
...keep the method as a method on your form, and pas that to start your new thread from (after all, a new thread doesn't have to be starting in a different class)
...change the access modifiers on your controls to be (say) internal such that any class within the same assembly can Invoke changes to the controls, or read from them.
...make your worker class a child of the form it needs to access - it can then see the privates of its parent, as long as it is passed a reference to the instance.

Communicate Between two threads

I have sth like that. It's giving me error. I cut out all unneeded parts of code. It is giving me this error
The calling thread cannot access this object because a different thread owns it.
public partial class MainWindow : Window
{
BackgroundWorker worker;
Grafik MainGrafik;
double ProgressBar
{
set { this.progressBarMain.Value = value; }
}
public MainWindow()
{
InitializeComponent();
worker = new BackgroundWorker();
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
MainGrafik = new Grafik();
MainGrafik.ProgressUpdate +=
new Grafik.ProgressUpdateDelegate(MainGrafik_ProgressUpdate);
worker.RunWorkerAsync();
}
void MainGrafik_ProgressUpdate(double progress)
{
ProgressBar = progress;
}
void worker_DoWork(object sender, DoWorkEventArgs e)
{
while(true)
{
MainGrafik.Refresh();
Thread.Sleep(2000);
}
}
}
class Grafik
{
public delegate void ProgressUpdateDelegate(double progress,
DateTime currTime);
public event ProgressUpdateDelegate ProgressUpdate;
public void Refresh()
{
ProgressUpdate(5); // Just for testing
}
}

You can't update UI objects from another thread. They have to be updated in the UI thread. Try adding this code to the MainGrafik_ProgressUpdate(double progress)
void MainGragfik_ProgressUpdate(double progress)
{
if (InvokeRequired)
{
BeginInvoke((MethodIvoker)(() =>
{
MainGragfik_ProgressUpdate(progress);
}));
return;
}
ProgressBar = progress;
}

The thread firing the ProgressUpdate event is your BackgroundWorker. The ProgressUpdate event handlers are likely running on that thread, and not the UI thread.

in short call this on the form in the context of your other thread's execution:
void MainGrafik_ProgressUpdate(object sender, EventArgs e) {
Action<T> yourAction =>() yourAction;
if(yourForm.InvokeRequired)
yourForm.Invoke(yourAction);
else yourAction;
}
Or with MethodInvoker (blank delegate)
void MainGrafik_ProgressUpdate(object sender, EventArgs e) {
MethodInvoker invoker = delegate(object sender, EventArgs e) {
this.ProgressBar = whatever progress;
};
}