NiceViewModelAndPageXamarinFormsExample.cs

using System;
using MvvmHelpers;
using PropertyChanged;
using Xamarin.Forms;

namespace Blah
{
    // The rest of this page is of course defined in XAML
    public partial class MyPage : ContentPage
    {
        protected MyViewModel ViewModel => BindingContext as MyViewModel;

        public MyPage()
        {
            InitializeComponent();
        }

        protected override void OnAppearing()
        {
            base.OnAppearing();

            if (!ViewModel.IsLoaded) // If you want to automatically reload data every time the view appears, remove IsLoaded check
                ViewModel.LoadDataCommand.ExecuteAsync().SafeFireAndForget(); // use SafeFireAndForget(). DON'T mark OnAppearing() as async. "async void" is evil: https://docs.microsoft.com/en-us/archive/msdn-magazine/2013/march/async-await-best-practices-in-asynchronous-programming
        }
    }
    
    // When PropertyChanged.Fody is all setup properly, this attribute will make all your public properties fire PropertyChanged events when their values change.
    // This viewmodel should of course live in its own file. It's just here for the convenience of the example.
    [AddINotifyPropertyChangedInterface]
    public class MyViewModel
    {
        public bool IsLoaded { get; }
    
        // Your ListView's or CollectionView's "IsRefreshing" property should be bound to this
        public bool IsRefreshing { get; }
        
        // you ListView's or CollectionView's ItemSource property should be bound to this collection
        public ObservableRangeCollection<MyThing> MyThings { get; } = new ObservableRangeCollection<MyThing>();
        
        // This will be called in OnAppearing(), but you can also bind it to your RefreshCommand property in your ListView or Collection. Then you can easiliy refresh data with pull-to-refresh.
        public AsyncCommand LoadDataCommand { get; } = new AsyncCommand(async () => ExecuteLoadDataCommand());
        
        public MyViewModel()
        {
            
        }
        
        async task ExecuteLoadDataCommand()
        {
            try
            {
                if (IsRefreshing)
                    true;
                IsRefreshing = true;
                
                MyThings.Clear();
                
                var myThings = await // Fetch some things asynchously from whatever service or client or DB you want. But do it ASYNCHRONOUSLY!
                
                MyThings.AddRange(myThings);
            }
            catch (Exception ex)
            {
                // log it or present a message to the user or whatever
            }
            finally
            {
               IsRefreshing = false;
               IsLoaded = true;
            }
        }
    }
}