practice/practiceApplicaiton/ClientsPage.xaml.cs

namespace practiceApplicaiton;

public partial class ClientsPage : ContentPage
{
    private Client? _selected;

    public ClientsPage() => InitializeComponent();

    protected override async void OnAppearing()
    {
        base.OnAppearing();
        await LoadAsync();
    }

    private async Task LoadAsync(string search = "")
    {
        try { ClientsList.ItemsSource = await Repository.GetClientsAsync(search); }
        catch (Exception ex) { await DisplayAlert("Ошибка", ex.Message, "OK"); }
    }

    private async void OnSearchChanged(object sender, TextChangedEventArgs e)
        => await LoadAsync(e.NewTextValue);

    private void OnSelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        _selected = e.CurrentSelection.FirstOrDefault() as Client;
        EditButton.IsEnabled = DeleteButton.IsEnabled = _selected != null;
    }

    private async void OnAddClicked(object sender, EventArgs e)
    {
        await Navigation.PushAsync(new ClientEditPage(null));
        await LoadAsync();
    }

    private async void OnEditClicked(object sender, EventArgs e)
    {
        if (_selected == null) return;
        await Navigation.PushAsync(new ClientEditPage(_selected));
        await LoadAsync();
    }

    private async void OnDeleteClicked(object sender, EventArgs e)
    {
        if (_selected == null) return;
        bool ok = await DisplayAlert("Удалить",
            $"Удалить клиента {_selected.FullName}?", "Да", "Отмена");
        if (!ok) return;
        try
        {
            await Repository.DeleteClientAsync(_selected.ClientId);
            await LoadAsync();
        }
        catch (Exception ex) { await DisplayAlert("Ошибка", ex.Message, "OK"); }
    }
}