Threadabortexception when calling showdialog in C#

Question

I have an application that parses a large XML file and builds WPF UI controls based on that content. This task usually takes about 15 - 30 seconds. In order to inform the user about a running task, I display a simple intermediate progress dialog window, like:

Thread progressDialogThread = new Thread(() =>
{
    Window window = new Window
    {
        Content = new ProgressDialog(),
        Height = 100,
        Width = 150,
        WindowStartupLocation = System.Windows.WindowStartupLocation.CenterScreen
    };
    window.ShowDialog();
});

progressDialogThread.SetApartmentState(ApartmentState.STA);
progressDialogThread.IsBackground = true;
progressDialogThread.Start();

buildUI();

progressDialogThread.Abort();

This works, but I sometimes get a ThreadAbortException on progressDialogThread.Start(), when the XML should be parsed once again.

Does anyone know a better approach to "close" the progress dialog?

Since the controls have to be built on the main UI thread, I can not use the backgroundworker...

The progress dialog itself in XAML looks like:

<UserControl x:Class="MyDialog.ProgressDialog"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:MyDialog"
        mc:Ignorable="d"
        Background="{DynamicResource MaterialDesignPaper}"
        TextElement.Foreground="{DynamicResource MaterialDesignBody}"
        Height="100" Width="150">
    <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
        <Label HorizontalAlignment="Center">Please wait</Label>
        <ProgressBar
          Style="{StaticResource MaterialDesignCircularProgressBar}"
          Value="0"
          IsIndeterminate="True" Width="40" Height="41" Margin="55,0" HorizontalAlignment="Center" VerticalAlignment="Center" />
    </StackPanel>
</UserControl>

Turn your buildUI into an async method? Have the code inside progressDialogThread store the reference to window in a shared place from where you can call .Close on it? — GSerg
– GSerg, Commented Jun 1, 2019 at 11:24
This is because you are calling Abort(), here is an example on how to use Abort() properly: link — muaz
– muaz, Commented Jun 1, 2019 at 11:44

Theraot · Accepted Answer · 2019-06-01 11:41:07Z

5

Do not abort a thread, that should be avoided.

If you want to close a Window, you call Close on it.

Oh, it is created by another thread? Alright, that is why the Window has a Dispatcher, you use BeginInvoke and it will run the callback on that thread.

In fact, there is a chance you do not need to create the Window in another thread※. You can create it in the main thread and have a background thread interact with it via BeginInvoke.

※: If you have the main thread busy and want the Window in another thread so the main thread does not block it (or viceversa), you probably should be using a BackgroundWorker (as Caius Jard suggests) instead of having a UI thread busy.

edited Jun 1, 2019 at 11:41

answered Jun 1, 2019 at 11:29

Theraot

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Comments

Caius Jard · Accepted Answer · 2019-06-01 11:14:03Z

2

Things like this are exactly what BackgroundWorker is for, and why it knows the difference between the UI thread and the work thread. Use a background worker, parse your XML file in the DoWork event handler (it will run on the background thread) and regularly report progress using the ReportProgress method while proceeding through DoWork's loop. The ProgressChanged handler code will execute on the UI thread, and it should poke the progress dialog to provide a status update on the process

answered Jun 1, 2019 at 11:14

Caius Jard

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6 Comments

PythonNoob Over a year ago

But it's not possible to add ui controls from another thread rather than the UI Thread.

Caius Jard Over a year ago

I'm not really sure what your comment means; add them to what?

Caius Jard Over a year ago

Still not making much sense

PythonNoob Over a year ago

Of course it makes sense... I want to add new controls, like TextBlock, Label etc. to a window, so you can't do this in a backgroundworker. stackoverflow.com/questions/3794420/…

Caius Jard Over a year ago

Why would you want to do that in a background worker? Surely you build your UI in design time, then you make an instance of it and show it - so show it, then start your bgworker, and let the bgworker report progress, and update the shown ui. I mean.. you can build the UI in runtime, but don't do it inside the DoWork of the background worker; do it on the main UI thread (the thing that starts the bgworker) if youre going to do it anywhere

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