Custom UserControl with ContentControl field

Question

I have a UserControl which acts as a wrapper for a ContentControl, which is simply a title to the ContentControl.

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>

<Grid Background="Green" Grid.Row="0">
    <TextBlock  Text="{Binding Header}" Style="{StaticResource HeaderStyle}" Margin="12, 10, 0, 10" />
</Grid>
    <ContentControl HorizontalAlignment="Stretch" HorizontalContentAlignment="Stretch" Content="{Binding Body}" Grid.Row="1"/>
</Grid>

And here's where I try to use the control:

<gbl:ListHeader Grid.Row="1" Visibility="{Binding HasMovies, Converter={StaticResource VisibilityConverter}}"  Header="{Binding Path=LocalizedResources.movie_list_header, Source={StaticResource LocalizedStrings}}" >
                    <gbl:ListHeader.Body>
                        <ListBox  SelectionChanged="ListBoxContainerSelectionChanged" ItemsSource="{Binding Movies}" ItemContainerStyle="{StaticResource HeaderListBoxItemStyle}">
                            <ListBox.ItemTemplate>
                                <DataTemplate>
                                    <gbl:MovieItemControl Header="{Binding MovieTitle}" Description="{Binding FormattedDescription}" Detail="{Binding FormattedDetail}" Opacity="{Binding IsSuppressed, Converter={StaticResource DimIfTrueConverter}}"/>
                                </DataTemplate>
                            </ListBox.ItemTemplate>
                        </ListBox>
                    </gbl:ListHeader.Body>

The DataBinding to the list happens, however nothing displays in the control. I'm guessing that it's still there, but too small to see (undefined h/w).

Is there something that I'm doing wrong? The header shows fine, so the control appears to be working somewhat.

Edit:

Here's the code-behind for ListHeader:

public partial class ListHeader : UserControl
    {
        private readonly ListHeaderData _data = new ListHeaderData();
        public ListHeader()
        {
            InitializeComponent();
            DataContext = _data;
        }

        public string Header
        {
            get { return (string)GetValue(HeaderProperty); }
            set { SetValue(HeaderProperty, value); }
        }

        // Using a DependencyProperty as the backing store for Header.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty HeaderProperty =
            DependencyProperty.Register("Header", typeof(string), typeof(ListHeader), new PropertyMetadata("",HeaderPropertyChanged) );

        private static void HeaderPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var lh = d as ListHeader;
            if (lh != null)
                lh._data.Header = e.NewValue as string;
        }



        public object Body
        {
            get { return GetValue(BodyProperty); }
            set { SetValue(BodyProperty, value); }
        }

        // Using a DependencyProperty as the backing store for Body.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty BodyProperty =
            DependencyProperty.Register("Body", typeof(object), typeof(ListHeader), new PropertyMetadata(null, BodyPropertyChanged));

        private static void BodyPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var lh = d as ListHeader;
            if (lh != null)
                lh._data.Body = e.NewValue;
        }
    }
    public class ListHeaderData : ViewModelBase
    {
        public ListHeaderData()
        {
            if (IsInDesignMode)
            {
                Header = "Custom Header Goes Here";
                Body = new Grid() { Background = new SolidColorBrush(Colors.Yellow) };
            }
        }
        private string _header;
        public string Header
        {
            get { return _header; }
            set { _header = value; RaisePropertyChanged("Header"); }
        }

        private object _body;
        public object Body
        {
            get { return _body; }
            set { _body = value; RaisePropertyChanged("Body");}
        }
    }

Answer 1

In addition to what i said in my comment you appear to bind to your DataContext in the UserControl declaration which is a Bad Thing and the problem of all this.

You appear to want to bind to the properties of the UserControl but you bind directly to the properties of the DataContext which is your ViewModel, hence setting the Body property on an instance in XAML does nothing as the property is sidestepped by the internal binding.

UserControls should for all i know do bindings like this:

<UserControl Name="control" ...>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <Grid Background="Green" Grid.Row="0">
            <TextBlock  Text="{Binding Header, ElementName=control}" Style="{StaticResource HeaderStyle}" Margin="12, 10, 0, 10" />
        </Grid>
        <ContentControl HorizontalAlignment="Stretch" HorizontalContentAlignment="Stretch" Content="{Binding Body, ElementName=control}" Grid.Row="1"/>
    </Grid>

---

Get rid of those dependency property changed callbacks and change the property code in ViewModels to this format to make sure it changed:

private int _MyProperty = 0;
public int MyProperty
{
    get { return _MyProperty; }
    set
    {
        if (_MyProperty != value)
        {
            _MyProperty = value;
            OnPropertyChanged("MyProperty");
        }
    }
}