How to use TreeDataTemplate with Menu

[martinrhan]

I have such a Menu

	<Menu Items="{Binding MenuItems}">
	  <Menu.DataTemplates>
		<TreeDataTemplate DataType="vm:MenuItemViewModel" ItemsSource="{Binding Items}">
		  <TreeDataTemplate.Content>
			<TextBlock Text="{Binding Header}"></TextBlock>
		  </TreeDataTemplate.Content>
		</TreeDataTemplate>
	  </Menu.DataTemplates>
	</Menu>

The ViewModel is:

    public class MenuItemViewModel : ViewModelBase {
        public ObservableCollection<MenuItemViewModel> Items { get; } = new();
        [Reactive]
        public required string Header { get; set; }
        [Reactive]
        public ICommand? Command { get; set; }
    }

        public MainWindowViewModel() {
            PopulateMenu();
        }
        public ObservableCollection<MenuItemViewModel> MenuItems { get; } = new();

        private void PopulateMenu() {
            MenuItemViewModel file = new MenuItemViewModel() {
                Header = "File",
            };
            MenuItemViewModel newWorld = new MenuItemViewModel() {
                Header = "New World..."
            };
            file.Items.Add(newWorld);
            MenuItems.Add(file);
        }

But when I run the app, only the top level MenuItem "File" is there, under "File" MenuItem nothing is displayed.

[maxkatz6]

There is no support for TreeDataTemplate in Menu control

[workgroupengineering]

You can use code like this:

    <Menu Items="{Binding MenuItems}">
      <Menu.ItemContainerTheme>
        <ControlTheme TargetType="MenuItem" x:DataType="l:Column" BasedOn="{StaticResource {x:Type MenuItem}}">
          <Setter Property="Header" Value="{Binding Header}"/>
          <Setter Property="Command" Value="{Binding Command}"/>
          <Setter Property="Items" Value="{Binding Items}"/>
        </ControlTheme>
      </Menu.ItemContainerTheme>
    </Menu>

[martinrhan]

The analyzer tell me unable to resolve type ControlTheme, and I cannot find this type in the API documentation as well.

[timunie]

Which Avalonia version do you use? This feature is only available in 11.0 preview releases. In 0.10.18 you need to use a Style instead.