unoplatform/uno · error · InvalidOperationException

Failed to load {e.SourcePageType.FullName}: {e.Exception}

Error message

Failed to load {e.SourcePageType.FullName}: {e.Exception}

What it means

Default OnNavigationFailed handler in the Uno 5.6 solution template (uno56netcurrent, integration-test app). Behaves like all Uno templates: when Frame navigation to SourcePageType fails, it wraps the inner exception in InvalidOperationException and re-throws, crashing the app. This template intentionally enables logging for all configurations to surface binding errors.

Source

Thrown at src/SolutionTemplate/5.6/uno56netcurrent/uno56netcurrent/App.xaml.cs:70

        MainWindow.SetWindowIcon();
        // Ensure the current window is active
        MainWindow.Activate();

        if (exitAfterLaunching)
        {
            await Task.Delay(1000);
            Exit();
        }
    }

    /// <summary>
    /// Invoked when Navigation to a certain page fails
    /// </summary>
    /// <param name="sender">The Frame which failed navigation</param>
    /// <param name="e">Details about the navigation failure</param>
    void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
    {
        throw new InvalidOperationException($"Failed to load {e.SourcePageType.FullName}: {e.Exception}");
    }

    /// <summary>
    /// Configures global Uno Platform logging
    /// </summary>
    public static void InitializeLogging()
    {
        // Logging must be enabled for all build configurations so that `.AddFakeLogging()` can be used to
        // catch binding errors in test and production builds.
        //
        // Performance is not a concern here.  This is an integration test.

        var factory = LoggerFactory.Create(builder =>
        {
#if __WASM__
            builder.AddProvider(new global::Uno.Extensions.Logging.WebAssembly.WebAssemblyConsoleLoggerProvider());
#elif __IOS__
            builder.AddProvider(new global::Uno.Extensions.Logging.OSLogLoggerProvider());

View on GitHub (pinned to 0418340488)

Solutions

1. Read e.Exception for the true root cause — the wrapped message is only identifying the page.
2. Use the enabled logging/FakeLogging output in this template to spot binding errors that precede the crash.
3. Confirm x:Class and project inclusion of the page type for the net-current target.
4. Replace the throw with diagnostics + e.Handled=true + fallback page for non-crashing behavior.

Example fix

// before
void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
{
    throw new InvalidOperationException($"Failed to load {e.SourcePageType.FullName}: {e.Exception}");
}

// after
void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
{
    _logger.LogError(e.Exception, "Nav failed: {Page}", e.SourcePageType?.FullName);
    e.Handled = true;
}

static bool CanNavigate(Frame f, Type page) => page != null && f.Content?.GetType() != page;

try { frame.Navigate(pageType); } catch (InvalidOperationException) { log.Error($"Integration-test nav failed: {pageType}"); frame.Navigate(typeof(ErrorPage)); }

When it happens

Trigger: Frame.Navigate to a page that throws during construction/XAML load, or to a type that cannot be activated in the net-current integration-test host.

Common situations: Page constructor throws (missing DI registration, null dependency), x:Class mismatch, resource/binding error caught by FakeLogging, or a platform guard excluding the page.

Related errors

• Failed to load {e.SourcePageType.FullName}: {e.Exception}
• Failed to load {e.SourcePageType.FullName}: {e.Exception}
• Failed to load {e.SourcePageType.FullName}: {e.Exception}
• Failed to load {e.SourcePageType.FullName}: {e.Exception}
• Failed to load {e.SourcePageType.FullName}: {e.Exception}

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/a42f636212b8d1dc. Report an issue: GitHub.