How to dynamically add MenuItems (with a header) to a WPF menu

Question

[Edit #3] - to anyone reading this question: do not under any circumstance use the approach outlined in this question. It is a Coding Horr

Answer 1

Another possible approach could be having the Menu be a region and agree on a convention so all views added to that region have a ViewModel with a property named MenuHeader. That way, the region adapter can simply get the menu header from the View's Data Context, and set it to the item when adding it.

Something similar is done in Prism with views added to a Tab Region. You can read more here.

I hope this provides some useful guidance.

Thanks, Damian

Answer 2

I'll confess that I haven't dug quite as deep into your example as maybe I should, but whenever I see code-behind that's searching the visual tree, I think, could this be handled more explicitly in a view model?

It seems to me in this case that you could come up with a pretty straightforward view model - an object exposing Text, Image, Command, and Children properties, for instance - and then create a simple data template that for presenting it as a MenuItem. Then anything that needs to alter the contents of your menus manipulates this model.

Edit:

Having looked at what you're up to in more detail, and the two examples you've linked to in your blog post, I am banging my head against the desk. Both of those developers appear to be under the misapprehension that the way to set properties on the menu items that are being generated by the template is to search through the visual tree in the ContentPresenter.Load event after they're created. Not so. That's is what the ItemContainerStyle is for.

If you use that, it's quite straightforward to create dynamic menus of the type you're describing. You need a MenuItemViewModel class that has INotifyPropertyChanged implemented and exposes these public properties:

string Text
Uri ImageSource
ICommand Command
ObservableCollection<MenuItemViewModel> Children

Using this:

<Menu DockPanel.Dock="Top" ItemsSource="{DynamicResource Menu}"/>

where the ItemsSource is an ObservableCollection<MenuItemViewModel>, and using this template:

<HierarchicalDataTemplate DataType="{x:Type local:MenuItemViewModel}"
                          ItemsSource="{Binding Path=Children}">
    <HierarchicalDataTemplate.ItemContainerStyle>
        <Style TargetType="MenuItem">
            <Setter Property="Command"
                    Value="{Binding Command}" />
        </Style>
    </HierarchicalDataTemplate.ItemContainerStyle>
    <StackPanel Orientation="Horizontal">
        <Image Source="{Binding ImageSource}" />
        <Label Content="{Binding Text}" />
    </StackPanel>
</HierarchicalDataTemplate>

the menus in the window exactly represent what's in the collection, and are dynamically updated as items are added and removed, both to the top-level items and to the descendants.

There's no clambering about in the visual tree, no manual creation of objects, no code-behind (other than in the view model, and in whatever populates the collection in the first place).

I've built a pretty thoroughly worked example of this; you can download the project here.