What are the best practices for handling asynchronous exceptions in MvvmCross

1. Use of BaseViewModel for Shared Error Handling**

In MvvmCross, using a `BaseViewModel` class is a common pattern for handling shared code, including error handling. This approach allows you to centralize error handling logic, making it easier to manage across different view models. For example, you can define a method like `GeneralAsyncLoad` in your `BaseViewModel` that handles exceptions during asynchronous operations[1][2].

2. App-Level Error Router**

Implementing an app-level "error router" is another effective strategy. This involves using interfaces like `IErrorReporter` and `IErrorSource` to route errors from view models to UI notifications. Each platform can then display errors in a way that is native to it, such as using `UIAlertViews` on iOS or `Toasts` on Android[2].

3. MvxNotifyTask for Async Operations**

MvvmCross provides `MvxNotifyTask`, which is a powerful tool for managing asynchronous operations. It allows you to monitor task states and handle exceptions gracefully without crashing the app. You can use `MvxNotifyTask` to wrap your async operations and handle exceptions through its `onException` parameter[4].

Example of Using MvxNotifyTask

csharp
public class MyViewModel : MvxViewModel
{
    private readonly ISomeService _someService;

    public MyViewModel(ISomeService someService)
    {
        _someService = someService;
    }

    public IMvxCommand MyCommand { get; private set; }

    private MvxNotifyTask _myTaskNotifier;

    public MvxNotifyTask MyTaskNotifier
    {
        get => _myTaskNotifier;
        private set => SetProperty(ref _myTaskNotifier, value);
    }

    public void Prepare()
    {
        MyCommand = new MvxCommand(() => MyTaskNotifier = MvxNotifyTask.Create(() => MyMethodAsync(), onException: ex => OnException(ex)));
    }

    private async Task MyMethodAsync()
    {
        await _someService.DoSomethingAsync();
    }

    private void OnException(Exception exception)
    {
        // Handle the exception here
    }
}

4. Avoiding Async Void Methods**

When handling asynchronous exceptions, it's crucial to avoid using `async void` methods unless they are event handlers. `Async void` methods do not return a `Task`, which means exceptions thrown by them cannot be caught using a `try-catch` block. Instead, they are raised directly on the SynchronizationContext, which can lead to unpredictable behavior[6][7].

5. Explicit Exception Handling in Lifecycle Methods**

In lifecycle methods like `OnCreate`, handle exceptions explicitly to prevent unexpected behavior. If you must call `async void` methods, ensure you handle exceptions within those methods as well, since they cannot be caught by the calling method[9].

6. Logging and Reporting Exceptions**

Finally, implement a robust logging mechanism to track and report exceptions. This can involve using services like `IErrorReporter` to log exceptions and notify users or developers about errors[1][2].

By following these practices, you can effectively manage asynchronous exceptions in MvvmCross applications, ensuring a more reliable and user-friendly experience.