CODEWITHSUNDEEP
c#wpfbackgroundworker
Anchit Pancholi
Anchit Pancholi

Reputation: 1204

C# WPF UI Freeze Issue MultiThreading

I have code like below and i am facing UI Hung issue, there is no direct way to reproduce it. its occurring randomly 1 out 10 times. I am not able to identify what is causing issue.

I have below button click code which will show a child window:-

private void processCart_Click(object sender, RoutedEventArgs e)
{
    // processcart is Child Window Like Dialog To Open on Top Of Main Window
    processcart = new ProcessCart();

    processcart.Closed += ProcessCart_OnClosed;

    // Disable Parent Window 
    this.Dispatcher.Invoke(new Action(() =>
    {
        try
        {
            this.IsEnabled = false;
        }
        catch (Exception ex)
        { }
    }));

    processcart.Owner = Window.GetWindow(this);

    // Openning Child Window
    processcart.Show();
}

private void ProcessCart_OnClosed(object sender, EventArgs e)
{
    // On Child Window Close Doing some UI Update on Main Window
    totalChangeAmount.Dispatcher.Invoke(new Action(() =>
    {
        try
        {
            totalChangeAmount.Text = XFuelMath.roundingTwo(cart.ChangeTotal) + "";
        }
        catch
        { }
    }));

    // Starting Background Worker Thread for Database operation.
    if (!bgwTransaction.IsBusy)
    {
        bgwTransaction.RunWorkerAsync(cart);
    }
}

private void bgwTransaction_DoWork(object sender, DoWorkEventArgs e)
{
    // Doing some database operation but no UI Operation 

    // I dont know if i can call task inside background worker. 
    Task.Run(() => DeleteCurrentTicketDataFromDB(dataList, false)); 

    // Calling another background worker inside it 
    if (!bgwPrintRecipt.IsBusy)
    {
        bgwPrintRecipt.RunWorkerAsync();
    }
}

private void bgwPrintRecipt_DoWork(object sender, DoWorkEventArgs e)
{
    // Sending Data to printer 
}

private void bgwPrintRecipt_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    // No Ui Operation Here 
}

private void bgwTransaction_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    // Some UI Operation 
    totalSurcharge.Dispatcher.Invoke(() =>
    {
        totalSurcharge.Text = "0";
    });

    saleNumber.Dispatcher.Invoke(() => { });

    saleDataGrid.Dispatcher.Invoke(new Action(() =>
    {
        try
        {
            saleDataGrid.ItemsSource = currentSharedTicketCollection;
            saleDataGrid.Items.Refresh();

            if (isautoscroll && item!=null)
            {
                saleDataGrid.ScrollIntoView(item, saleDataGrid.Columns[0]);
                saleDataGrid.SelectedItem = item;
            }
        }
    }));

    // Enable the parent window Again 
    this.Dispatcher.Invoke(new Action(() =>
    {
        try
        {
            this.IsEnabled = true;
        }
        catch (Exception ex)
        { }
    }));
}

I am not sure if i am calling BackgroundWorker inside do DoWork and RunWorkerCompleted. Please guide me what i need to change in this code?

Upvotes: 0

Views: 1693

Answers (1)

Alois Kraus
Alois Kraus

Reputation: 13535

You should remove the Dispatcher call in your processCart_Click handler this will execute in the same UI thread and is not necessary at all unless you have several WPF windows in different threads created.

Besides that you should attach a debugger to the hung process and see where it hangs. If you have no debugger installed on the machine where it is executed you can right click in Task Manager and create a dump file. That file can be loaded into Visual Studio.

If your application is a 32 bit application executing on Windows x64 you need to close task manager and start the one from C:\Windows\SysWOW64\Taskmgr.exe to take a 32 bit dump on 64 bit Windows. If you do not do this you cannot load it into VS with managed call stacks.

Upvotes: 1

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