Combine design time menu elements into databound menu item binding - wpf

Question

Hopefully I got the vernacular right on my question so I don't throw people completely off.
I have a menu that is data bound and using a HierarchicalDataTemplate that handles the various nested types in my binding object. So far everything is working fantastically; but now I would like to add a couple additional menu items to menu items of a certain type, but of course that breaks the binding as I cannot bind to a collection that already contains elements. CompositeCollection seems to be what I am looking for but I keep running into syntax errors when trying to apply that to my HierarchicalDataTemplate.
<Menu.Resources>
<HierarchicalDataTemplate DataType="{x:Type ODIF:PluginContainer}" ItemsSource="{Binding Instance.Devices}">
<HierarchicalDataTemplate.ItemsSource>
<CompositeCollection>
<CollectionContainer Collection="{Binding Instance.Devices}"/>
<MenuItem>One more item!</MenuItem>
<MenuItem>Two more items!</MenuItem>
</CompositeCollection>
</HierarchicalDataTemplate.ItemsSource>
<StackPanel HorizontalAlignment="Left" Orientation="Horizontal">
<Image Source="{Binding PluginIcon}" Width="16" Height="16">
<Image.Style>
<Style TargetType="{x:Type Image}">
<Style.Triggers>
<DataTrigger Binding="{Binding PluginIcon}" Value="{x:Null}">
<Setter Property="Visibility" Value="Collapsed" />
</DataTrigger>
</Style.Triggers>
</Style>
</Image.Style>
</Image>
<TextBlock Text="{Binding PluginName}"/>
</StackPanel>
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type ODIF:Device}" ItemsSource="{Binding InputChannels}">
<StackPanel HorizontalAlignment="Left" Orientation="Horizontal">
<Image Source="{Binding StatusIcon}" Width="16" Height="16">
<Image.Style>
<Style TargetType="{x:Type Image}">
<Style.Triggers>
<DataTrigger Binding="{Binding StatusIcon}" Value="{x:Null}">
<Setter Property="Visibility" Value="Collapsed" />
</DataTrigger>
</Style.Triggers>
</Style>
</Image.Style>
</Image>
<TextBlock Text="{Binding DeviceName}"/>
</StackPanel>
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type ODIF:DeviceChannel}">
<local:ChannelBox Channel="{Binding}" Width="200" Click="ChannelClicked"/>
</HierarchicalDataTemplate>
</Menu.Resources>
This throws:
The specified value cannot be assigned. The following type was
expected: "BindingBase".
and
Property 'ItemsSource' does not support values of type 'CompositeCollection'.

Answer 1

I guess you have to use a converter for solving your issue.
Let's suppose that MenuModel is a class which represents a menu item. It is really simple:
public class MenuModel
{
private List<MenuModel> children = new List<MenuModel>();
public string Description { get; set; }
public IList Children
{
get
{
return children;
}
}
}
Now we have our XAML:
<Window.Resources>
<collections:ArrayList x:Key="someOtherMenus">
<local:MenuModel Description="Menu A">
<local:MenuModel.Children>
<local:MenuModel Description="SubMenu i" />
<local:MenuModel Description="SubMenu ii" />
</local:MenuModel.Children>
</local:MenuModel>
<local:MenuModel Description="Menu B" />
</collections:ArrayList>
</Window.Resources>
<DockPanel>
<Menu DockPanel.Dock="Top" Margin="3" ItemsSource="{Binding MenuModels}">
<Menu.ItemTemplate>
<HierarchicalDataTemplate>
<HierarchicalDataTemplate.ItemsSource>
<Binding ConverterParameter="someOtherMenus">
<Binding.Converter>
<local:CompositeCollectionConverter />
</Binding.Converter>
</Binding>
</HierarchicalDataTemplate.ItemsSource>
<TextBlock Text="{Binding Description}" Margin="3" />
</HierarchicalDataTemplate>
</Menu.ItemTemplate>
</Menu>
<TextBlock Text="text" Margin="10" />
</DockPanel>
So now we can consider the converter implementation:
public class CompositeCollectionConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
MenuModel menuModel = value as MenuModel;
if (parameter != null)
{
CollectionContainer collectionContainer = new CollectionContainer();
collectionContainer.Collection = menuModel.Children;
CompositeCollection compositeCollection = new CompositeCollection();
compositeCollection.Add(collectionContainer);
collectionContainer = new CollectionContainer();
collectionContainer.Collection = (IEnumerable)App.Current.MainWindow.FindResource(parameter);
compositeCollection.Add(collectionContainer);
return compositeCollection;
}
else
{
return menuModel.Children;
}
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotSupportedException();
}
}
As you can see it uses its parameter to get a specific resource (in our case I am using the resource called "someOtherMenus", which is an IEnumerable of MenuModels).
Of course the HierarchicalDataTemplate is recursive so the "someOtherMenus" MenuModels will be added to each level (but the first one) of your Menu.
I hope my sample can help you.