XamlParseException was unhandled.

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Hi there. I faced the problem debugging my WPF-WCF simple chat application. There's an exception like:

XamlParseException was unhandled. 'The invocation of the constructor on type 'ChatGUI.MainWindow' that matches the specified binding constraints threw an exception.' Line number '3' and line position '9'.

I see that's a XAML exception, so here's the XAML code listing:

XML

<Window x:Class="ChatGUI.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="35*" />
            <RowDefinition Height="35" />
        </Grid.RowDefinitions>
        <TextBox Height="Auto" HorizontalAlignment="Stretch" Margin="6,6,6,6" Name="textBoxChatPane" VerticalAlignment="Stretch" Width="Auto" Grid.Row="0" />
        <TextBox Height="23" HorizontalAlignment="Stretch" Margin="6,6,6,6" Name="textBoxEntryField" VerticalAlignment="Stretch" Width="Auto" Grid.Row="1" KeyDown="textBoxEntryField_KeyDown" />
    </Grid>
</Window>

Have you ever seen the same problem? I would be glad to see every useful advice.
Thanks in advance.

Posted 5-Jan-12 11:24am

valecoder

Updated 5-Jan-12 17:12pm

Mehdi Gholam

v2

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valecoder 5-Jan-12 17:50pm

The same cs class:

namespace ChatGUI
{
///

/// Interaction logic for MainWindow.xaml
///

public partial class MainWindow : Window
{
private ChatBackend.ChatBackend _backend;

public MainWindow()
{
InitializeComponent();
_backend = new ChatBackend.ChatBackend(this.DisplayMessage);
}

public void DisplayMessage(ChatBackend.CompositeType composite)
{
string username = composite.Username == null ? "" : composite.Username;
string message = composite.Message == null ? "" : composite.Message;
textBoxChatPane.Text += (username + ": " + message + Environment.NewLine);
}

private void textBoxEntryField_KeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Return || e.Key == Key.Enter)
{
_backend.SendMessage(textBoxEntryField.Text);
textBoxEntryField.Clear();
}
}
}
}

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Espen Harlinn · Accepted Answer · 2012-01-05T12:01:00

Solution 1

My guess is that this line:
_backend = new ChatBackend.ChatBackend(this.DisplayMessage);
throws an exception.

Try setting a breakpoint on the line and debug your application.

If you open the App.xaml, you'll see that the ChatGUI.MainWindow is referenced there.

Best regards
Espen Harlinn

Posted 5-Jan-12 12:01pm

Espen Harlinn

Comments

valecoder 5-Jan-12 18:09pm

Yep. I've just done that. And the point is in this line.

Wendelius 5-Jan-12 18:11pm

Spot on, +5.

Perhaps it's a personal problem but I find the error handling in XAML window constructors a bit annoying. It would be nice if the debugger would actually stop on the problem statement when an unhandled exception is raised regardless of the compile settings but...

Espen Harlinn 5-Jan-12 18:16pm

Thanks Mika!
You can change the behaviour using Mainmenu->Debug->Exceptions

Wendelius 5-Jan-12 18:22pm

Yes, but id I remember correctly, this doesn't apply for release builds, even if run from Visual Studio :)

Espen Harlinn 5-Jan-12 18:24pm

So that's what you meant by "regardless of the compile settings" :)

Wendelius 5-Jan-12 18:57pm

Yes :)

valecoder 5-Jan-12 18:14pm

Yeah. Thanks a lot.

Espen Harlinn 5-Jan-12 18:17pm

Nice that it worked out :)

valecoder 5-Jan-12 18:18pm

Sorry for delay :)

Joezer BH 18-Feb-14 8:19am

5ed!

Espen Harlinn 18-Feb-14 8:22am

Thank you :-)

Joezer BH 18-Feb-14 8:52am

Fact is that you hit the spot in this answer, google would reveal that there are scores of questions about the exact same exception and many can be answered simply by noticing what happens right after the "InitializeComponent();".
Any code that will throw an exception there will probably result in the same "XamlParseException was unhandled. 'The invocation of the constructor on type 'ChatGUI.MainWindow' that matches the specified binding constraints threw an exception.' Line number '3' and line position '9'." notice...

I think it's worth publishing this fact as a CP Tip.

Cheers, Canny