AutoCatAvalonia/AutoCat/Windows/MainWindow.axaml.cs

using System.Linq;
using AutoCat.Pages;
using AutoCat.ViewModels;
using Avalonia.Controls;
using FluentAvalonia.UI.Controls;

namespace AutoCat.Windows;

public partial class MainWindow : Window
{
    private readonly SettingsPage _settingsPage = new SettingsPage();
    private readonly HistoryPage _historyPage = new HistoryPage();
    private readonly SearchPage _searchPage = new SearchPage();
    
    public MainWindow()
    {
        InitializeComponent();

        NavView.SelectionChanged += NavSelectionChanged;
        NavView.ItemInvoked += NavViewOnItemInvoked;
        NavView.SelectedItem = NavView.MenuItems.First(x => (x as NavigationViewItem)?.Tag?.ToString() == "History");
    }

    private void NavViewOnItemInvoked(object? sender, NavigationViewItemInvokedEventArgs e)
    {
        switch (e.InvokedItemContainer.Tag)
        {
            case "Check":
                ShowCheckNumberDialog();
                break;
        }
    }

    private void NavSelectionChanged(object? sender, NavigationViewSelectionChangedEventArgs args)
    {
        if (args.IsSettingsSelected)
        {
            NavView.Content = _settingsPage;
        }
        else if (args.SelectedItem is NavigationViewItem item)
        {
            NavView.Content = item.Tag switch
            {
                "History" => _historyPage,
                "Search" => _searchPage,
                _ => NavView.Content
            };
        }
    }

    private async void ShowCheckNumberDialog()
    {
        var dialog = new ContentDialog()
        {
            Title = "Check new number",
            CloseButtonText = "Cancel"
        };

        var dialogContent = new CheckNumberDialog();
        dialog.Content = dialogContent;
        
        var dialogTask = dialog.ShowAsync();
        
        if (dialogContent.DataContext is CheckNumberViewModel vm)
        {
            vm.AutoCloseEvent += async (_, _) =>
            {
                dialog.Hide();
                if (_historyPage.DataContext is HistoryViewModel hvm && vm.Vehicle != null)
                {
                    await hvm.AddVehicle(vm.Vehicle);
                    NavView.Content = _historyPage;
                }
            };
        }

        await dialogTask;
    }
}