Debugging WPF databinding issues

Lately due to switching teams and project I've been doing much more WPF than before. I cannot say I have fully mastered the learning curve yet but I'm getting better and it is an interesting journey.

Occasionally the data bindings does not work as expected and then it is nice to get more information about them in order to figure out what went wrong.

The following is useful when you want to know why a particular binding is misbehaving (or rather you want to know where you screwed up...)

xmlns:diagnostics="clr-namespace:System.Diagnostics;assembly=WindowsBase"

ItemsSource="{Binding <snip>, diagnostics:PresentationTraceSources.TraceLevel=High}"

The above information and MUCH more is presented by Beatriz Stollnitz

(This post is also a 'reminder to self')

Enumerating XAML (BAML) files in an Assembly

I wanted to play around with XAML Pages, and wanted an application that automagically showed me a list of all included (embedded) XAML files in an assembly without me doing more than adding the XAML file to the project.

This turned out to be tricky until you got it...

Well, it is simple when you know how to do it, but until then you'll have some googling to do. (At least that is  my experience)

Basically, a XAML file with a build action of Page or Resource ends up in a .resources file named <assemblyname>.g.resources. This .resources file contains the binary version of the XAML file (BAML).

Enumerating the contents of a .resources file can be done using the System.Resources.ResourceReader class as follows:

using (ResourceReader reader = new ResourceReader("Foo.g.resources"))
{
    foreach (DictionaryEntry entry in reader)
    {
        Console.WriteLine(entry.Key);
    }
}

So all that's left to do is to create the application, (and no, it ain't pretty but it works):

MainForm.xaml:

<Window x:Class="AutoToc.MainForm"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:sys="clr-namespace:System;assembly=system" 
    Title="AutoToc" Height="400" Width="600" Loaded="FormLoaded"
    >
  <Window.Resources>    
    <HierarchicalDataTemplate DataType="{x:Type sys:Uri}">
      <BulletDecorator VerticalAlignment="Center">
        <BulletDecorator.Bullet>
          <Ellipse Fill="BlueViolet" Width="5" Height="5" 
                   VerticalAlignment="Center"/>
        </BulletDecorator.Bullet>
        <TextBlock Text="{Binding Path=OriginalString}" 
                   Margin="5,0,0,0" VerticalAlignment="Center" />
      </BulletDecorator>
    </HierarchicalDataTemplate>
  </Window.Resources>
    <Grid>
      <Grid.ColumnDefinitions>
        <ColumnDefinition Width="200"/>
        <ColumnDefinition Width="Auto"/>
        <ColumnDefinition Width="*"/>
      </Grid.ColumnDefinitions>
      <TreeView Grid.Column="0" Name="tocTree" 
                ItemsSource="{Binding}"
                SelectedItemChanged="tocTreeSelectedItemChanged"></TreeView>
      <GridSplitter Grid.Column="1" Width="2" HorizontalAlignment="Left" 
                    VerticalAlignment="Stretch"/>
      <Frame Name="contentFrame" Grid.Column="2" NavigationUIVisibility="Hidden" 
             VerticalAlignment="Stretch" HorizontalAlignment="Stretch"/>
    </Grid>
</Window>

and the interesting parts of the code behind:

private void FormLoaded(object sender, RoutedEventArgs e)
{
    // UriCollection inherits ObservableCollection<Uri>
    UriCollection pages = new UriCollection();
    Assembly asm = Assembly.GetExecutingAssembly();
    Stream stream = asm.GetManifestResourceStream(asm.GetName().Name + ".g.resources");

    DataContext = pages;
    using (ResourceReader reader = new ResourceReader(stream))
    {
        foreach (DictionaryEntry entry in reader)
        {
            // for some curious reason, we get "cannot locate resource"
            // if we leave the .baml extension, it needs to be .xaml !?!
            pages.Add(new Uri(((string)entry.Key).Replace(".baml", ".xaml"),
                UriKind.Relative));

        }
    }
}

private void tocTreeSelectedItemChanged(object sender, RoutedEventArgs e)
{
    contentFrame.Source = tocTree.SelectedItem as Uri;
}

That was easy, wasn't it?

Obviously this is not production quality code but more a proof of concept, and yes, I do use it for playing around with the 3D samples...

Obviously, it would be better to filter out non-Page xaml files, such as mainform ...

Playing around in WPF land

With a little (ok, a lot of) help from Josh Smith and Karsten Januszewski/Andrew Whiddett I managed to put together a little ComicBook application that utilizes Asynchronous databinding, animated image transitions. It's not quite finished yet, but the parts that are left should mostly be a walk in the park (i.e. known territory). Not bad for an evenings worth of work, considering this is my first "real" WPF application.

The learning curve is steep...

I probably post more technical stuff when I get it closer to what I want it to be.