dotnet/wpf · error · InvalidOperationException

SR.BamlIsNotSupportedOutsideOfApplicationResources

Error message

SR.BamlIsNotSupportedOutsideOfApplicationResources

What it means

BamlConverterCore throws SR.BamlIsNotSupportedOutsideOfApplicationResources when the baseUri of the stream is not a pack-application URI (BaseUriHelper.IsPackApplicationUri fails). BAML streams must originate from application resources (pack://application:,,,); BAML from arbitrary external URIs is rejected because compiled BAML is only meaningful/trusted within the application's own resources.

Solutions

1. Reference the BAML via a pack application URI, e.g. new Uri("pack://application:,,,/MyAssembly;component/Page.xaml").
2. Ensure the resource is embedded as Page/Resource build action in the application assembly rather than Content or an external file.
3. If the content is external, ship XAML instead of BAML since external BAML is unsupported.

Example fix

// before
frame.Source = new Uri("file:///C:/app/Page.baml");
// after
frame.Source = new Uri("pack://application:,,,/MyApp;component/Page.xaml");

if (!BaseUriHelper.IsPackApplicationUri(uri))
    throw new ArgumentException("BAML can only be loaded from a pack application URI");

try { LoadBaml(uri); }
catch (InvalidOperationException) { /* convert content to XAML or fix the URI */ }

When it happens

Trigger: BamlConverter invoked with a baseUri such as an http(s) URL, a site-of-origin pack URI, or a file path rather than a pack application URI.

Common situations: Pointing Frame/NavigationService at a .baml on disk or a remote server; misconfigured source URIs after moving a resource from the application assembly to loose content.

Understand the failure class

Background: "Invalid URL" / "URL cannot be empty": fix the malformed or missing URL behind request-construction failures — this error's family across 50 libraries.

Related errors

• SR.EntryAssemblyIsNull
• SR.NonPackAppAbsoluteUriNotAllowed
• Can't Assign to Known Type attributes
• Could not find prefix for type
• Found unexpected Xmlns BAML record

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/27fdef3c67e76ee1. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/AppModel/AppModelKnownContentFactory.cs:43

        // Creates an object instance from a Baml stream and it's Uri
        // </summary>
        internal static object BamlConverter(Stream stream, Uri baseUri, bool canUseTopLevelBrowser, bool sandboxExternalContent, bool allowAsync, bool isJournalNavigation, out XamlReader asyncObjectConverter)
        {
            return BamlConverterCore(stream, baseUri, canUseTopLevelBrowser, sandboxExternalContent, allowAsync, isJournalNavigation, out asyncObjectConverter, false);
        }

        internal static object BamlConverterCore(Stream stream, Uri baseUri, bool canUseTopLevelBrowser, bool sandboxExternalContent, bool allowAsync, bool isJournalNavigation, out XamlReader asyncObjectConverter, bool isUnsafe)
        {
            asyncObjectConverter = null;
            if (isUnsafe)
            {
                throw new InvalidOperationException(SR.Format(SR.BamlIsNotSupportedOutsideOfApplicationResources));
            }
            // If this stream comes from outside the application throw
            //
            if (!BaseUriHelper.IsPackApplicationUri(baseUri))
            {
                throw new InvalidOperationException(SR.BamlIsNotSupportedOutsideOfApplicationResources);
            }

            // If this stream comes from a content file also throw
            Uri partUri = PackUriHelper.GetPartUri(baseUri);
            string partName, assemblyName, assemblyVersion, assemblyKey;
            BaseUriHelper.GetAssemblyNameAndPart(partUri, out partName, out assemblyName, out assemblyVersion, out assemblyKey);
            if (ContentFileHelper.IsContentFile(partName))
            {
                throw new InvalidOperationException(SR.BamlIsNotSupportedOutsideOfApplicationResources);
            }

            ParserContext pc = new ParserContext
            {
                BaseUri = baseUri,
                SkipJournaledProperties = isJournalNavigation
            };

            return Application.LoadBamlStreamWithSyncInfo(stream, pc);

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