C#•7mo ago

✅ ERROR: The calling thread cannot access this object because a different thread owns it.

Hey, I'm getting this error The calling thread cannot access this object because a different thread owns it. from the following method when trying to add a Run element to a RichTextBox I've tried Googling a ton and even tried ChatGPT to see if it could fix it for me, all answers point to use chatRichTextBox.Dispatcher.Invoke but it still fails, any ideas?

private void AddChatMessage(string username, string message, System.Drawing.Color usernameColor)
{
    System.Windows.Media.Color mediaColor = System.Windows.Media.Color.FromArgb(usernameColor.A, usernameColor.R, usernameColor.G, usernameColor.B);

    var usernameRun = new Run(username)
    {
        Foreground = new SolidColorBrush(mediaColor),
        FontWeight = FontWeights.Bold
    };
    var messageRun = new Run(": " + message)
    {
        Foreground = Brushes.White
    };

    var paragraph = new Paragraph();
    paragraph.Inlines.Add(usernameRun);
    paragraph.Inlines.Add(messageRun);

    // Ensure the UI update is done on the UI thread
    chatRichTextBox.Dispatcher.Invoke(() =>
    {
        chatRichTextBox.Document.Blocks.Add(paragraph);
        chatRichTextBox.ScrollToEnd();
    });
}

private void AddChatMessage(string username, string message, System.Drawing.Color usernameColor)
{
    System.Windows.Media.Color mediaColor = System.Windows.Media.Color.FromArgb(usernameColor.A, usernameColor.R, usernameColor.G, usernameColor.B);

    var usernameRun = new Run(username)
    {
        Foreground = new SolidColorBrush(mediaColor),
        FontWeight = FontWeights.Bold
    };
    var messageRun = new Run(": " + message)
    {
        Foreground = Brushes.White
    };

    var paragraph = new Paragraph();
    paragraph.Inlines.Add(usernameRun);
    paragraph.Inlines.Add(messageRun);

    // Ensure the UI update is done on the UI thread
    chatRichTextBox.Dispatcher.Invoke(() =>
    {
        chatRichTextBox.Document.Blocks.Add(paragraph);
        chatRichTextBox.ScrollToEnd();
    });
}

10 Replies

leowest•7mo ago

Instead of using a ricthtextbox, you could use a itemscontrol, u create a datatemplate add some scrolling then you can use an ObservableCollection<Message> and instead of all that u would just add items to the Observable collection and it would update your ui This is just an idea:

<Grid Margin="10">
    <ScrollViewer VerticalScrollBarVisibility="Auto">
        <ItemsControl ItemsSource="{Binding Messages}">
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <TextBlock>
                        <Run Foreground="{Binding UsernameColor}" FontWeight="Bold" Text="{Binding Username}" />
                        <Run Foreground="{Binding MessageColor}" Text=": " />
                        <Run Foreground="{Binding MessageColor}" Text="{Binding Message}" />
                    </TextBlock>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </ScrollViewer>
</Grid>

<Grid Margin="10">
    <ScrollViewer VerticalScrollBarVisibility="Auto">
        <ItemsControl ItemsSource="{Binding Messages}">
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <TextBlock>
                        <Run Foreground="{Binding UsernameColor}" FontWeight="Bold" Text="{Binding Username}" />
                        <Run Foreground="{Binding MessageColor}" Text=": " />
                        <Run Foreground="{Binding MessageColor}" Text="{Binding Message}" />
                    </TextBlock>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </ScrollViewer>
</Grid>

And by adding items to:

public ObservableCollection<ChatMessage> Messages { get; set; } = new ObservableCollection<ChatMessage>();

public ObservableCollection<ChatMessage> Messages { get; set; } = new ObservableCollection<ChatMessage>();

It would populate the ItemsControl https://wpf-tutorial.com/list-controls/itemscontrol/

Delicious CakeOP•7mo ago

That's an excellent example! Unfortunately it still gives me this error when I try to add the messages :( Line:

ChatHistoryCollection.Add(new ChatMessage { UsernameColour= new SolidColorBrush(mediaColor), Username = username, Message = message });

Error:

System.NotSupportedException: 'This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread.'

leowest•7mo ago

yes now u have to use the dispatcher because you're calling it from a different thread

Delicious CakeOP•7mo ago

Am I doing something wrong in the MainWindow constructor?

public MainWindow()
{
    InitializeComponent();
    _synthesizer = new SpeechSynthesizer();
    InitializeTwitchClient();
    DataContext = this;
}

public MainWindow()
{
    InitializeComponent();
    _synthesizer = new SpeechSynthesizer();
    InitializeTwitchClient();
    DataContext = this;
}

Ah okay I'll give that a go first Like this?

Application.Current.Dispatcher.Invoke(() =>
{
    ChatHistoryCollection.Add(new ChatMessage { UsernameColour = new SolidColorBrush(mediaColor), Username = username, Message = message });
});

Application.Current.Dispatcher.Invoke(() =>
{
    ChatHistoryCollection.Add(new ChatMessage { UsernameColour = new SolidColorBrush(mediaColor), Username = username, Message = message });
});

leowest•7mo ago

should work ChatHistoryCollection is a public property right?

Delicious CakeOP•7mo ago

That worked! Not getting the colour I expected from the username though, that might be cause either converting it wrong or grabbing the wrong value from TwitchLib's OnMessageReceivedArgs

leowest•7mo ago

yeah I wouldn't know about that I never used that lib and if u want the messages order to be inverted just change it to Insert(0, new ChatMessage.... instead of Add then u avoid having to scroll unless u want to see old messages

Delicious CakeOP•7mo ago

Amazing, thank you for the help :)

leowest•7mo ago

no worries, $close

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✅ ERROR: The calling thread cannot access this object because a different thread owns it.