MyFirstMAUI/MyFirstMauiApp/UseRestService/ViewModels/PartsViewModel.cs

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using CommunityToolkit.Mvvm.Messaging;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using UseRestService.Data;

namespace UseRestService.ViewModels
{
    internal partial class PartsViewModel : ObservableObject
    {
        [ObservableProperty]
        ObservableCollection<Part> _parts;

        [ObservableProperty]
        bool _isRefreshing = false;

        [ObservableProperty]
        bool _isBusy = false;

        [ObservableProperty]
        Part _selectedPart;

        public PartsViewModel()
        {
            _parts = new ObservableCollection<Part>();

            WeakReferenceMessenger.Default.Register<RefreshMessage>(this, async (r, m) =>
            {
                await LoadData();
            });

            Task.Run(LoadData);
        }

        [RelayCommand]
        async Task PartSelected()
        {
            if (SelectedPart == null)
                return;

            var navigationParameter = new Dictionary<string, object>()
            {
                { "part", SelectedPart }
            };

            await Shell.Current.GoToAsync("addpart", navigationParameter);

            MainThread.BeginInvokeOnMainThread(() => SelectedPart = null);
        }

        [RelayCommand]
        async Task LoadData()
        {
            if (IsBusy)
                return;

            try
            {
                IsRefreshing = true;
                IsBusy = true;

                var partsCollection = await PartsManager.GetAll();

                MainThread.BeginInvokeOnMainThread(() =>
                {
                    Parts.Clear();

                    foreach (Part part in partsCollection)
                    {
                        Parts.Add(part);
                    }
                });
            }
            finally
            {
                IsRefreshing = false;
                IsBusy = false;
            }
        }

        [RelayCommand]
        async Task AddNewPart()
        {
            await Shell.Current.GoToAsync("addpart");
        }
    }
}