gistfile1.cs

public class MainViewModel : ReactiveObject
{
    public MainViewModel()
    {
        LoadTweetsCommand = new ReactiveCommand();
        LoadTweetsCommand.RegisterAsync(_ => {
            throw new Exception("AA");
            return LoadTweets();
        }).Subscribe(x => TheTweets = x);

        var errorMessage = "The Tweets could not be loaded";
        var errorResolution = "Check your Internet connection";

        // Any exceptions thrown by LoadTweets will end up being
        // sent through ThrownExceptions
        LoadTweetsCommand.ThrownExceptions
            .Select(ex => new UserError(errorMessage, errorResolution))
            .SelectMany(UserError.Throw)
            .Where(x => x == RecoveryOptionResult.RetryOperation)
            .InvokeCommand(LoadTweetsCommand);

        UserError.RegisterHandler(e => Observable.Return(RecoveryOptionResult.));
    }


    public int TheTweets { get; set; }

    private IObservable<int> LoadTweets()
    {
        return Observable.Return(0);
    }

    public ReactiveCommand LoadTweetsCommand { get; set; }
}