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POWPF: Binding to single complex item
 

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  1. POWPF: Binding to single complex item
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    <p>In my application, I use a UserControl instance to display the contents of a complex type that implements INotifyPropertyChanged that is a ViewModel to display the current state of background processes. This ViewModel is exposed to the UserControl as a DependencyProperty.</p> <p>The DependencyProperty is being set nicely, and events are happily sent out by the ViewModel. However, it seems that WPF's data binding is giving me a slight headache. (Plus, I wouldn't count myself as an expert on WPF; the problem and its solution may be simple, but it's eluding me.)</p> <p>Basically, all I see is "Initialzing" on my UI, which is the DependencyProperty's default value, and the fallback value used for binding. If I alter the DependencyProperty's default value, the UI shows these values instead. If I remove the DependencyProperty's default value (ie. <code>null</code>), it uses the fallback values.</p> <p>What I actually wanted is to display the ViewModel's contents.</p> <hr> <p>View model:</p> <pre><code>public class ImportInformation : INotifyPropertyChanged { /* ... */ } </code></pre> <p>User control:</p> <pre><code>public partial class ImportTab : UserControl { public static readonly DependencyProperty ValueProperty = DependencyProperty .Register("ValueProperty", typeof(ImportInformation), typeof(ImportTab), new PropertyMetadata(new ImportInformation { TaskName = "Initializing...", CurrentTask = "Initializing...", Progress = Double.NaN })); public ImportInformation Value { get { return (ImportInformation)GetValue(ValueProperty); } set { SetValue(ValueProperty, value); } } public ImportTab() { InitializeComponent(); } } </code></pre> <p>XAML:</p> <pre><code>&lt;UserControl x:Class="LingImp.Tabs.ImportTab" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:conv="clr-namespace:LingImp.Converters" mc:Ignorable="d" Name="root" d:DesignHeight="300" d:DesignWidth="300"&gt; &lt;UserControl.Resources&gt; &lt;conv:NaNConverter x:Key="nanConv"/&gt; &lt;/UserControl.Resources&gt; &lt;StackPanel Orientation="Vertical"&gt; &lt;TextBlock Padding="0,4,0,4" TextWrapping="Wrap"&gt; Your import is currently being processed. Depending on the data source, this can take a long, &lt;Italic&gt;long&lt;/Italic&gt; time. &lt;/TextBlock&gt; &lt;GroupBox VerticalAlignment="Top" HorizontalAlignment="Left" MinWidth="150" DataContext="{Binding ElementName=root, Path=Value}"&gt; &lt;GroupBox.Header&gt; &lt;TextBlock FontWeight="Bold" Text="{Binding Path=TaskName, Mode=OneWay, FallbackValue=Initializing...}"/&gt; &lt;/GroupBox.Header&gt; &lt;StackPanel Orientation="Vertical" Margin="4"&gt; &lt;TextBlock TextWrapping="Wrap" Text="{Binding Path=CurrentTask, Mode=OneWay, FallbackValue=Initializing...}" Margin="0,0,0,2"/&gt; &lt;ProgressBar MinHeight="9" HorizontalAlignment="Stretch" Minimum="0" Maximum="1" IsIndeterminate="{Binding Path=Progress, Mode=OneWay, FallbackValue=true, Converter={StaticResource nanConv}}" Value="{Binding ElementName=root, Path=Value.Progress, Mode=OneWay, FallbackValue=0}"/&gt; &lt;TextBlock FontSize="11" HorizontalAlignment="Right" Text="{Binding Path=Progress, Mode=OneWay, FallbackValue=0, StringFormat=\{0:P\}}"/&gt; &lt;/StackPanel&gt; &lt;/GroupBox&gt; &lt;/StackPanel&gt; &lt;/UserControl&gt; </code></pre>
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    1. CO1. Do your setters in `ImportInformation` raise the `PropertyChanged` event? 2. How do you update your ImportInformation? 3. Does the "output" window of Visual Studio show any binding errors?
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    2. COSorry if I skipped that class. I thought it would be too long and boring to post :-) But yes, the event is being triggered properly when another background thread sets its values. I did however just notice, that no one subscribed to the PropertyChanged event, so my guess is that the problem lies in my XAML snippet.
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