MyFirstMAUI/MyFirstMauiApp/NotesNet8/ViewModels/NotesViewModel.cs

using CommunityToolkit.Mvvm.Input;
using NotesNet8.Models;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;

namespace NotesNet8.ViewModels
{
    internal class NotesViewModel : IQueryAttributable
    {
        public ObservableCollection<NoteViewModel> AllNotes { get; }
        public ICommand NewCommand { get; }
        public ICommand SelectNoteCommand { get; }

        public NotesViewModel()
        {
            AllNotes = new ObservableCollection<NoteViewModel>(Note.LoadAll().Select(n => new NoteViewModel(n)));
            NewCommand = new AsyncRelayCommand(NewNoteAsync);
            SelectNoteCommand = new AsyncRelayCommand<NoteViewModel>(SelectNoteAsync);
        }

        public void ApplyQueryAttributes(IDictionary<string, object> query)
        {
            if (query.ContainsKey("deleted"))
            {
                string noteId = query["deleted"].ToString();
                NoteViewModel matchedNote = AllNotes.Where(n => n.Identifier == noteId).FirstOrDefault();
                if (matchedNote != null)
                    AllNotes.Remove(matchedNote);
            }
            else if (query.ContainsKey("saved"))
            {
                string noteId = query["saved"].ToString();
                NoteViewModel matchedNote = AllNotes.Where(n => n.Identifier == noteId).FirstOrDefault();
                if (matchedNote != null)
                {
                    matchedNote.Reload();
                    AllNotes.Move(AllNotes.IndexOf(matchedNote), 0);
                }
                else
                    AllNotes.Insert(0, new NoteViewModel(Note.Load(noteId)));
            }
        }

        private async Task NewNoteAsync()
        {
            await Shell.Current.GoToAsync(nameof(Views.NotePage));
        }

        private async Task SelectNoteAsync(ViewModels.NoteViewModel note)
        {
            if (note != null)
                await Shell.Current.GoToAsync($"{nameof(Views.NotePage)}?load={note.Identifier}");
        }
    }
}