YOUserbase/UserOverviewPage.xaml.cs

using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;

namespace YOUserbase;

public partial class UserOverviewPage : ContentPage {
    public int _index = 0;

    private string details;
    private string firstname;
    private string lastname;
    private string birthDate;
    public string Details { get => details; set => SetProperty(ref details, value); }
    public string Firstname { get => firstname; set => SetProperty(ref firstname, value); }
    public string Lastname { get => lastname; set => SetProperty(ref lastname, value); }
    public string BirthDate { get => birthDate; set => SetProperty(ref birthDate, value); }

    public UserOverviewPage() {
        InitializeComponent();
        users.ItemsSource = Data.Users;
    }

    private async void OnAdd(object sender, EventArgs e) {
        await Navigation.PushAsync(new CreateUserPage());
        Console.WriteLine(Data.Users);
    }

    private async void OnDeleteItem(object sender, EventArgs e) {
        Button btn = (Button) sender;
        var id = Int32.Parse(btn.ClassId);
        var user = Data.Users.FirstOrDefault(usr => usr.Id == id);
        var action = await DisplayAlert("Irreversible action", "Do you really want to delete this user?", "Yes", "No");
        if(action) {
            Data.Users.Remove(user);
        }
    }

    private async void OnEditItem(object sender, EventArgs e) {
        Button btn = (Button) sender;
        var id = Int32.Parse(btn.ClassId);
        var user = Data.Users.FirstOrDefault(usr => usr.Id == id);
        await Navigation.PushAsync(new CreateUserPage(user));
    }

    protected bool SetProperty<T>(ref T field, T newValue, [CallerMemberName] string propertyName = null) {
        if(!Equals(field, newValue)) {
            field = newValue;
            return true;
        }
        return false;
    }
}