Ursa.Avalonia/demo/Ursa.Demo/ViewModels/NavMenuDemoViewModel.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Threading.Tasks;
using System.Windows.Input;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using Ursa.Controls;
namespace Ursa.Demo.ViewModels;

public class NavMenuDemoViewModel: ObservableObject
{
    private MenuItem? _selectedMenuItem;

    public MenuItem? SelectedMenuItem
    {
        get=>_selectedMenuItem;
        set => SetProperty(ref _selectedMenuItem, value);
    }
    public ObservableCollection<MenuItem> MenuItems { get; set; } = new ObservableCollection<MenuItem>
    {
        new MenuItem { Header = "Introduction" , Children =
        {
            new MenuItem() { Header = "Getting Started", Children =
            {
                new MenuItem() { Header = "Code of Conduct" },
                new MenuItem() { Header = "How to Contribute" },
                new MenuItem() { Header = "Development Workflow" },
            }},
            new MenuItem() { Header = "Design Principles"},
            new MenuItem() { Header = "Contributing", Children =
            {
                new MenuItem() { Header = "Code of Conduct" },
                new MenuItem() { Header = "How to Contribute" },
                new MenuItem() { Header = "Development Workflow" },
            }},
        }},
        new MenuItem { Header = "Controls", IsSeparator = true},
        new MenuItem { Header = "Badge" },
        new MenuItem { Header = "Banner" },
        new MenuItem { Header = "ButtonGroup" },
        new MenuItem { Header = "Class Input" },
        new MenuItem { Header = "Dialog" },
        new MenuItem { Header = "Divider" },
        new MenuItem { Header = "Drawer" },
        new MenuItem { Header = "DualBadge" },
        new MenuItem { Header = "EnumSelector" },
        new MenuItem { Header = "ImageViewer" },
        new MenuItem { Header = "IPv4Box" },
        new MenuItem { Header = "IconButton" },
        new MenuItem { Header = "KeyGestureInput" },
        new MenuItem { Header = "Loading" },
        new MenuItem { Header = "MessageBox" },
        new MenuItem { Header = "Navigation" },
        new MenuItem { Header = "NavMenu" },
        new MenuItem { Header = "NumericUpDown" },
        new MenuItem { Header = "Pagination" },
        new MenuItem { Header = "RangeSlider" },
        new MenuItem { Header = "SelectionList" },
        new MenuItem { Header = "TagInput" },
        new MenuItem { Header = "Timeline" },
        new MenuItem { Header = "TwoTonePathIcon" },
        new MenuItem { Header = "ThemeToggler" }
    };

    public ICommand RandomCommand { get; set; }
    public NavMenuDemoViewModel()
    {
        RandomCommand = new RelayCommand(OnRandom);
    }

    private void OnRandom()
    {
        var items = GetLeaves();
        var index = new Random().Next(items.Count);
        SelectedMenuItem = items[index];
    }
    
    private List<MenuItem> GetLeaves()
    {
        List<MenuItem> items = new();
        foreach (var item in MenuItems)
        {
            items.AddRange(item.GetLeaves());
        }

        return items;
    }
}

public class MenuItem
{
    static Random r = new Random();
    
    public string? Header { get; set; }
    public int IconIndex { get; set; }
    public bool IsSeparator { get; set; }
    public ICommand NavigationCommand { get; set; }

    public MenuItem()
    {
        NavigationCommand = new AsyncRelayCommand(OnNavigate);
        IconIndex = r.Next(100);
    }

    private async Task OnNavigate()
    {
        await MessageBox.ShowOverlayAsync(Header??string.Empty, "Navigation Result");
    }

    public ObservableCollection<MenuItem> Children { get; set; } = new ObservableCollection<MenuItem>();

    public IEnumerable<MenuItem> GetLeaves()
    {
        if (this.Children.Count == 0)
        {
            yield return this;
            yield break;
        }

        foreach (var child in Children)
        {
            var items = child.GetLeaves();
            foreach (var item in items)
            {
                yield return item;
            }
        }
    }
}