Question

I’m trying to bind the SelectedItem to a View. But the view is not able to access the viewmodel when it is inside the Resources block.
When the datacontext is re-assigned to the children, the binding works for textblocks but not for UserControl (NoteView)

Am I missing any Binding?

PFB revised(entire) code and inline comments.

<UserControl x:Class="Konduva.View.NoteSearchView"
<!-- other namespaces here -->
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
DataContext="{Binding NoteSearch, Source={StaticResource Locator}}">
    <Grid>
    <ListView ItemsSource="{Binding Notes}"               
        SelectedItem="{Binding SelectedNote}">
        <ListView.Resources>
        <DataTemplate DataType="{x:Type vm:NoteViewModel}">
                    <DockPanel>
                        <TextBlock Text="{Binding Title}" />
                        <Popup Placement="Right"
                           PlacementTarget="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=ListViewItem}}"
                           IsOpen="{Binding (ListViewItem.IsSelected), RelativeSource={RelativeSource FindAncestor, AncestorType=ListViewItem}}"
                           DataContext="{Binding Path=DataContext, RelativeSource={RelativeSource AncestorType={x:Type ListView}}}">
                            <StackPanel>
  <!-- This is working -->      <TextBlock Text="{Binding SelectedNote.Title}" />
  <!-- This is not working -->  <v:NoteView DataContext="{Binding SelectedNote}" />                                
                            </StackPanel>
                        </Popup>
                    </DockPanel>
                </DataTemplate>
            </ListView.Resources>            
        </ListView>  
    </Grid>
</UserControl>

NoteView:

<Grid>
    <TextBlock Text="{Binding Title}" /> // This Text is not displayed
</Grid>

Answer 1

Update 3
Since you’re using MvvmLight: in NoteView, try changing

DataContext="{Binding Note, Source={StaticResource Locator}}"

to

<UserControl.Style>
    <Style TargetType="UserControl">
        <Setter Property="DataContext" Value="{Binding Note, Source={StaticResource Locator}}"/>
    </Style>
</UserControl.Style>

Update 2

Encountered a similar problem a few minutes ago which I didn’t fully understand so I’ll throw in the same solution here to see if it helps. What happends if you change it to this?

<v:NoteView DataContext="{Binding RelativeSource={RelativeSource AncestorType={x:Type Popup}},
                                  Path=DataContext.SelectedNote}"/>

Update

I’m unable to reproduce this. Try adding this in your NoteView constructor. Do you reach DataContextChangedHandler when you change the selection in the ListView?

public NoteView()
{
    InitializeComponent();
    DependencyPropertyDescriptor dpd = 
        DependencyPropertyDescriptor.FromProperty(UserControl.DataContextProperty, 
                                                  typeof(UserControl));
    if (dpd != null)
    {
        dpd.AddValueChanged(this, new EventHandler(DataContextChangedHandler));
    }
}
void DataContextChangedHandler(object sender, EventArgs e)
{
    MessageBox.Show("DataContext Changed: " + DataContext);
}

First answer

Your DockPanel will get the NoteViewModel as a DataContext and not the ListView and since this DataContext is inherited by all Childs every child will end up with a NoteViewModel as DataContext. To use the ListView as a DataContext for the Popup you can do this. I’m not sure what the DataContext Binding for the StackPanel does though, so I might be missing something here..

<DataTemplate DataType="{x:Type vm:NoteViewModel}">
    <DockPanel>
        <TextBlock Text="{Binding Title}" />
        <Popup Placement="Right" 
               PlacementTarget="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=ListViewItem}}" 
               IsOpen="{Binding (ListViewItem.IsSelected), RelativeSource={RelativeSource FindAncestor, AncestorType=ListViewItem}}"
               DataContext="{Binding Path=DataContext, RelativeSource={RelativeSource AncestorType={x:Type ListView}}}">
            <StackPanel>
                <TextBlock Text="{Binding SelectedNote.Title}" />
                <StackPanel>
                    <v:NoteView DataContext="{Binding SelectedNote}"/>
                </StackPanel>
            </StackPanel>
        </Popup>
    </DockPanel>
</DataTemplate>