How do I get Prism to report the exceptions it traps?

Question

I have a Prism WPF application which failed to load one of its modules when I deployed it (due to a database problem). On my development machine, I can see the relevant exceptions being thrown (and apparently caught and handled by Prism) in the Output window of Visual Studio.

I was able to solve the immediate problem by doing this:

public MyModuleViewConstructor()
{
    try
    {
        // some startup work here
        // ...
        InitializeComponent();
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.ToString(), "A System Error Occurred.");
    }
}

Which surfaces the error in production so that I can take action on it. But I would still like to obtain the messages from any exceptions that are thrown during normal operations, So, in the spirit of Prism's way of doing things, I did this:

public class Logger : ILoggerFacade
{
    public void Log(string message, Category category, Priority priority)
    {
        using (StreamWriter s = File.AppendText("Log.txt"))
        {
            s.WriteLine(string.Format("{0}-{1}: {2}", DateTime.Now.ToString("MM/dd/yyyy HH:mm:ss.ffff"), priority.ToString(), message));
            s.Close();
        }
    }
}

And registered it in the Bootstrapper:

class Bootstrapper : DryIocBootstrapper
{
    private readonly Logger _logger = new Logger();

    protected override ILoggerFacade CreateLogger()
    {
        return _logger;
    }
}

This works splendidly for normal log entries such as debug logging. But it still does not log any exceptions thrown within my application.

How do I get Prism to log thrown exceptions in my application?

Answer 1

When navigating, all exceptions that occur during view and/or view model creation are caught by the region manager. Those are not logged by default (although this would be a cool feature).

You can, however, be notified about the exception and log it yourself or react otherwise.

To do that, navigate through one of the IRegionManager.RequestNavigate( ..., Action<NavigationResult> navigationCallback ) overloads. The navigationCallback will be passed a result object that contains any exception in the NavigationResult.Error property.