PrismLibrary/Prism · error · NavigationException

NavigationException.UnsupportedMauiCreation

NavigationException.UnsupportedMauiCreation

Error message

NavigationException.UnsupportedMauiCreation

What it means

During page creation Prism walks the exception chain and, if any inner exception message contains 'thread with a dispatcher', concludes that a MAUI UI element was created off the UI thread — an unsupported creation pattern — and throws NavigationException.UnsupportedMauiCreation instead of the generic ErrorCreatingPage.

Solutions

1. Invoke navigation on the main thread: await MainThread.InvokeOnMainThreadAsync(() => _navigationService.NavigateAsync(...))
2. Remove UI element construction from background threads/Task.Run in constructors or OnInitialized
3. If in a service/worker, marshal to the dispatcher of the main page (IDispatcherProvider) before navigating

Example fix

// before
Task.Run(() => _navigationService.NavigateAsync("ViewB"));
// after
await MainThread.InvokeOnMainThreadAsync(() => _navigationService.NavigateAsync("ViewB"));

if (!MainThread.IsMainThread) throw new InvalidOperationException("Navigate only on the UI thread");

try { await _navigationService.NavigateAsync(segment); }
catch (NavigationException ne) when (ne.Message == NavigationException.UnsupportedMauiCreation)
{ await MainThread.InvokeOnMainThreadAsync(() => _navigationService.NavigateAsync(segment)); }

When it happens

Trigger: Navigating (creating a Page/ViewModel) from a background thread or Task.Run so a control's constructor touches main-thread-only APIs, surfacing 'thread with a dispatcher' in the inner exception chain.

Common situations: Triggering navigation from an event on a non-UI thread; deep-link handling in a background service; async work that resumes on a non-UI SynchronizationContext and then navigates.

Understand the failure class

Background: "unsupported platform" / "not supported on this platform" errors: what they mean and how to fix them — this error's family across 47 libraries.

Related errors

• The page type ' ' is not supported.
• Unable to determine the current page.
• NavigationException.NoPageIsRegistered
• The builder does not implement IRegistryAware
• NavigationException.NoPageIsRegistered

AI-assisted analysis of PrismLibrary/Prism@358118cd64 (2026-09-15). Data as JSON: /api/errors/111e2700ffae6ce8. Report an issue: GitHub.

Appendix: source

Thrown at src/Maui/Prism.Maui/Navigation/PageNavigationService.cs:964

        {
            throw new NavigationException(NavigationException.NoPageIsRegistered, segmentName, knfe);
        }
        catch(ViewModelCreationException vmce)
        {
            throw new NavigationException(NavigationException.ErrorCreatingViewModel, segmentName, _pageAccessor.Page, vmce);
        }
        //catch(ViewCreationException viewCreationException)
        //{
        //    if(!string.IsNullOrEmpty(viewCreationException.InnerException?.Message) && viewCreationException.InnerException.Message.Contains("Maui"))
        //        throw new NavigationException(NavigationException.)
        //}
        catch (Exception ex)
        {
            var inner = ex.InnerException;
            while(inner is not null)
            {
                if (inner.Message.Contains("thread with a dispatcher"))
                    throw new NavigationException(NavigationException.UnsupportedMauiCreation, segmentName, _pageAccessor.Page, ex);
                inner = inner.InnerException;
            }
            throw new NavigationException(NavigationException.ErrorCreatingPage, segmentName, ex);
        }
    }

    protected virtual Page CreatePageFromSegment(string segment)
    {
        string segmentName = UriParsingHelper.GetSegmentName(segment);
        var page = CreatePage(segmentName);
        if (page is null)
        {
            var innerException = new NullReferenceException(string.Format("{0} could not be created. Please make sure you have registered {0} for navigation.", segmentName));
            throw new NavigationException(NavigationException.NoPageIsRegistered, segmentName, _pageAccessor.Page, innerException);
        }

        return page;
    }

View on GitHub (pinned to 358118cd64)