HarryPotterApp: CharactersListViewModel.cs

CharactersListViewModel.cs

using System;
using System.Windows.Input;
using System.Threading.Tasks;
using System.Collections.ObjectModel;

using HarryPotterApp.Models;

using Xamarin.Forms;

namespace HarryPotterApp.ViewModels
{
    public class CharactersListViewModel : BaseViewModel
    {
        private ObservableCollection<CharacterViewModel> _characters;

        public ObservableCollection<CharacterViewModel> Characters
        {
            get { return _characters; }
            set { _characters = value; OnPropertyChanged(); }
        }

        private CharacterViewModel _selectedCharacter;

        public CharacterViewModel SelectedCharacter
        {
            get { return _selectedCharacter; }
            set { _selectedCharacter = value; OnPropertyChanged(); }
        }

        public ICommand SearchByNameCommand { private set; get; }
        public ICommand GoToDetailsCommand { private set; get; }
        public ICommand AddNewCharacterCommand { private set; get; }

        public INavigation Navigation { get; set; }

        public CharactersListViewModel(INavigation navigation)
        {
            Navigation = navigation;

            SearchByNameCommand = new Command<string>(async (name) => await LoadData(name));
            GoToDetailsCommand = new Command<Type>(async (pageType) => await GoToDetails(pageType));
            AddNewCharacterCommand = new Command<Type>(async (pageType) => await AddNewCharacter(pageType));
        }

        async Task LoadData(string name)
        {
            Characters = new ObservableCollection<CharacterViewModel>();
            var hpCharacters = string.IsNullOrWhiteSpace(name)
                ? await App.Context.GetItemsAsync<HPCharacter>()
                : await App.Context.FilterItemsAsync<HPCharacter>("HPCharacter", $"name LIKE '%{name}%'");

            foreach (var item in hpCharacters)
                Characters.Add(new CharacterViewModel(item));
        }

        async Task GoToDetails(Type pageType)
        {
            if (SelectedCharacter != null)
            {
                var page = (Page)Activator.CreateInstance(pageType);
                page.BindingContext = new CharacterDetailsViewModel(SelectedCharacter);
                await Navigation.PushAsync(page);

                SelectedCharacter = null;
            }
        }

        async Task AddNewCharacter(Type pageType)
        {
            SelectedCharacter = null;

            var page = (Page)Activator.CreateInstance(pageType);
            page.BindingContext = new CharacterDetailsViewModel(new CharacterViewModel());
            await Navigation.PushAsync(page);
        }
    }
}