How to handle "cannot find view for viewmodel" in Caliburn Micro?

Question

in my solution I have code like this:

public async Task<bool> Execute(string target)
{
    var screen = navigationService.NavigateTo(target) as Screen;
    await screen.TaskCompletionSource.Task;
    return true;
}

Due to nature of solution sometimes it could be possible that ViewModel that we are navigating to, not always have corresponding View. That is resulting in ugly window with unformatted message:

Cannot find view for viewmodel

Is it possible to recognize this situation and how to handle it? For example by terminating screen or redirecting to another one?

Answer 1

You could use ViewLocator for the purpose.

if ((ViewLocator.LocateForModelType(typeof(DummyViewModel), null, null) is TextBlock tb
    && tb.Text.StartsWith("Cannot find", StringComparison.InvariantCultureIgnoreCase)))
{
    // View does not exist, Terminate or redirect to another
}
else
{
    // View found, redirect to intended one
}