使用 Xamarin MVVM Prism 通过 Searchbar 中的 TextChanged 事件更新 ListView

Question

I'm using MVVM Prism in Xamarin Forms. I'm accessing an API to GET records and I'm assigning it to an ObservableCollections.

I'm trying to figure out how to work my TextChanged EventToCommandBehavior on my SearchBar. The event trigger is working, what I'm trying to fix is the automatic update of my ListView while typing. I can do this when using the code behind, but now I want to use the MVVM Prism approach and put all my codes in my View Model.

I also tried creating ListView in my ViewModel and pass my ObservableCollection to it so I can use it as bindable object in my View but it is also not working, or maybe I am doing it wrong.

VIEW MODEL

 public class CoinsPageViewModel : BindableBase
        {
            public ObservableCollection<CoinsModel> coinsModel { get; set; }
            private ICoins _icoins;
            public INavigationService NavigationService { get; set; }

            private DelegateCommand<string> _textChangedCommand { get; set; }
            public DelegateCommand<string> TextChangedCommand => 
                _textChangedCommand ?? (_textChangedCommand = new DelegateCommand<string>(TextChanged));
    
            private async void TextChanged(string obj)
            {
                var coins = await _icoins.GetCoinsList();
                var keyword = _searchText;
                var searchResult = coinsModel.Where(c => c.Name.ToLower().Contains(keyword.ToLower()));
                
                //----DISPLAY SEARCH RESULT TO THE BINDABLE OBJECT IN VIEW----
            }
    
            public CoinsPageViewModel(ICoins coins, INavigationService navigationService)
            {
                coinsModel = new ObservableCollection<CoinsModel>();
                _icoins = coins;
                LoadCoins();
                NavigationService = navigationService;
            }
    
            private string _searchText;
            public string SearchText
            {
                get { return _searchText; }
                set { SetProperty(ref _searchText, value); }
            }
    
            public async void LoadCoins()
            {
                var coins = await _icoins.GetCoinsList();
                foreach (var coin in coins)
                {
                    coinsModel.Add(coin);
                }
            }
    
            private CoinsModel _selectedCoin;
            public CoinsModel SelectedCoin
            {
                get { return _selectedCoin; }
                set 
                { 
                    _selectedCoin = value;
                    if (_selectedCoin != null)
                    {
                        var navigationParamaters = new NavigationParameters();
                        navigationParamaters.Add("coinsid", _selectedCoin.Id);
                        NavigationService.NavigateAsync("CoinsDetailsPage", navigationParamaters);
                    }
                }
            }
    
        }

VIEW

 <ContentPage.Content>
            <Grid>
                <StackLayout>
                    <SearchBar TextColor="White" 
                               Text="{Binding SearchText}"
                               BackgroundColor="#6b120a" 
                               Placeholder="Search" 
                               PlaceholderColor="White" 
                               CancelButtonColor="White">
                        <SearchBar.Behaviors>
                            <prism:EventToCommandBehavior EventName="TextChanged"
                                                          Command="{Binding TextChangedCommand}"
                                                          CommandParameter="Text">
                            </prism:EventToCommandBehavior>
                        </SearchBar.Behaviors>
                    </SearchBar>
    
                    <ListView SeparatorColor="#d96818" 
                              x:Name="LvCoins"
                              ItemsSource="{Binding coinsModel}"
                              SelectedItem="{Binding SelectedCoin}"
                              Margin="5"                         
                              HasUnevenRows="True" 
                              androidSpecific:ListView.IsFastScrollEnabled="True">
                              
                        <ListView.ItemTemplate>
                            <DataTemplate>
                                <ViewCell>
                                    <Grid HorizontalOptions="Fill">
                                        <Grid.ColumnDefinitions>
                                            <ColumnDefinition Width="auto"/>
                                            <ColumnDefinition Width="auto"/>
                                        </Grid.ColumnDefinitions>
    
                                        <StackLayout Margin="5,5,0,0">
                                            <Label Text="{Binding Name}" 
                                                   VerticalOptions="Center" 
                                                   FontSize="15" TextColor="Black" 
                                                   FontFamily="Chunkfive"/>
                                            <Label Text="{Binding Symbol}" 
                                                   VerticalOptions="Center" 
                                                   FontSize="15" TextColor="#6b120a" 
                                                   FontAttributes="Bold"/>
                                        </StackLayout>
                                    </Grid>
                                </ViewCell>
                            </DataTemplate>
                        </ListView.ItemTemplate>
                    </ListView>
                </StackLayout>
            </Grid>
        </ContentPage.Content>

INTERFACE and MODEL

   public interface ICoins
        {
            Task<List<CoinsModel>> GetCoinsList();
            Task<CoinsDetailModel> GetCoinsDetails(string id);
        }

public class CoinsModel
        {
            [JsonProperty("id")]
            public string Id { get; set; }
            [JsonProperty("symbol")]
            public string Symbol { get; set; }
            [JsonProperty("name")]
            public string Name { get; set; }
            public string NameSort => Name[0].ToString();
        }
    

SCREENSHOT

Answer 1

I already found the best fix for this. I installed the NuGet package PropertyChanged.Fody and it fixed all my issues. I don't need to write SetProperty nor Implement the INotifyPropertyChanged at all. I also create a List which will be used by my Search event. Thank you all.