PrismLibrary/Prism · error · ViewRegistrationException

Resources.OnViewRegisteredException (formatted with…

Error message

Resources.OnViewRegisteredException (formatted with e.RegionName, rootException)

What it means

Prism.Maui wraps an exception thrown while registering a view with a region in a ViewRegistrationException. It formats Resources.OnViewRegisteredException with the region name and the root (innermost) exception, preserving the original as InnerException. This exists so region wiring failures surface a clear message naming the offending region instead of an opaque internal error.

Solutions

Inspect InnerException (rootException) to find the real failure and fix that underlying issue.
Ensure the view type is registered in the container before RegisterViewWithRegion is called.
Verify a region adapter exists for the control hosting the region (or register one).
Check the region name matches the registered name exactly (case/typo).

Example fix

// before: ViewRegistrationException with opaque inner stack
containerRegistry.RegisterForNavigation<MyRegionView>(); // missing
// after: register the view and adapter first
containerRegistry.RegisterForNavigation<MyRegionView>();
containerRegistry.RegisterForNavigation<MyContentControlAdapter>();

Defensive patterns

Strategy: try-catch

Validate before calling

if (containerRegistry == null || view == null || string.IsNullOrWhiteSpace(regionName)) throw new InvalidOperationException("Invalid region registration inputs");

Type guard

if (string.IsNullOrWhiteSpace(regionName) || view is null) return;

Try / catch

try
{
    regionManager.RegisterViewWithRegion(regionName, viewType);
}
catch (ViewRegistrationException ex)
{
    logger.LogError(ex.InnerException ?? ex, "View registration failed for region {Region}", regionName);
}

Prevention

Register all region views with the DI container before navigation.
Confirm a region adapter exists for each host control type.
Log InnerException — the wrapper hides the real cause.

When it happens

Trigger: The ContentRegistered event handler (OnContentRegistered) catches an exception raised by a view registry adapter (e.g. IRegionAdapter creation for the registered view/region) and rethrows it via OnViewRegisteredException. Any failure inside region adapter creation, view resolution, or region behavior attachment during RegisterViewWithRegion triggers it.

Common situations: View type not registered in the DI container when a region tries to create it; region adapter missing for the target control; a region behavior throwing during attachment; typo'd region name registered with a nonexistent adapter.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of PrismLibrary/Prism@358118cd64 (2026-09-15). Data as JSON: /api/errors/7a87a8e74df29b2b. Report an issue: GitHub.

Appendix: source

Thrown at src/Maui/Prism.Maui/Navigation/Regions/RegionViewRegistry.cs:106

    private void OnContentRegistered(ViewRegisteredEventArgs e)
    {
        try
        {
            _contentRegisteredListeners.Raise(this, e);
        }
        catch (TargetInvocationException ex)
        {
            Exception rootException;
            if (ex.InnerException != null)
            {
                rootException = ex.InnerException.GetRootException();
            }
            else
            {
                rootException = ex.GetRootException();
            }

            throw new ViewRegistrationException(string.Format(CultureInfo.CurrentCulture,
                Resources.OnViewRegisteredException, e.RegionName, rootException), ex.InnerException);
        }
    }
}

View on GitHub (pinned to 358118cd64)