Xamarin Forms: Display error occurring in view model - xamarin.forms

Question

I'm following tutorials/examples for a Xamarin Forms project, where there is a view with a C# code-behind, binding to a view model. However, I want to catch an exception occurring in the view model and display it in an alert or use any other common technique for displaying errors.
Here is the view, which reloads data using a refresh:
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="MyCompany.App.Views.DashboardPage"
xmlns:vm="clr-namespace:MyCompany.App.ViewModels"
xmlns:dashboard="clr-namespace:MyCompany.App.ViewModels.Dashboard;assembly=MyCompany.App"
Title="{Binding Title}">
...
<RefreshView x:DataType="dashboard:DashboardViewModel" Command="{Binding LoadItemsCommand}" IsRefreshing="{Binding IsBusy, Mode=TwoWay}">
... content
</RefreshView>
</ContentPage>
Then I have the C# code behind for the XAML:
public partial class DashboardPage : ContentPage
{
DashboardViewModel _viewModel;
public DashboardPage()
{
InitializeComponent();
BindingContext = _viewModel = new DashboardViewModel();
}
protected override void OnAppearing()
{
base.OnAppearing();
_viewModel.OnAppearing();
}
}
And finally the view model where the loading happens. It inherits from the BaseViewModel which is provided in the tutorials.
public class DashboardViewModel : BaseViewModel
{
private DashboardItemViewModel _selectedItem;
public ObservableCollection<DashboardItemViewModel> Items { get; }
public Command LoadItemsCommand { get; }
public Command<DashboardItemViewModel> ItemTapped { get; }
public DashboardViewModel()
{
Title = "Dashboard";
Items = new ObservableCollection<DashboardItemViewModel>();
LoadItemsCommand = new Command(async () => await ExecuteLoadItemsCommand());
ItemTapped = new Command<DashboardItemViewModel>(OnItemSelected);
}
async Task ExecuteLoadItemsCommand()
{
IsBusy = true;
try
{
Items.Clear();
var items = await GetItems();
foreach (var item in items)
{
Items.Add(item);
}
}
finally
{
IsBusy = false;
}
}
private static async Task<List<DashboardItemViewModel>> GetItems()
{
// Where errors happen
return items;
}
public void OnAppearing()
{
IsBusy = true;
SelectedItem = null;
}
public DashboardItemViewModel SelectedItem
{
get => _selectedItem;
set
{
SetProperty(ref _selectedItem, value);
OnItemSelected(value);
}
}
async void OnItemSelected(DashboardItemViewModel item)
{
if (item == null || item.Uri.IsNotSet())
return;
await Shell.Current.GoToAsync(item.Uri);
}
}
I can't see any overridable methods in ContentPage for catching exceptions. What's the best way to catch an exception and display it in an alert?

Answer 1

I'm not sure what exactly you want, but for catching errors I use try/catch method.
try
{
//your code here
}
catch(Exception exc)
{
await App.Current.MainPage.DisplayAlert("Warning", "Error: " + exc, "Ok");
}