dotnet/wpf · error · ArgumentException

SR.InvalidScheme

Error message

SR.InvalidScheme

What it means

ByteRangeDownloader's constructor only accepts URIs with the http or https scheme, because it downloads bytes from a web server using HTTP range requests. Passing any other scheme (e.g. pack://, file://, ftp://) makes the constructor throw an ArgumentException keyed by SR.InvalidScheme. The comparison is case-sensitive ordinal since Uri.Scheme is contractually lowercase.

Solutions

1. Pass an absolute http:// or https:// URI to the constructor
2. Resolve the pack:// URI to its underlying HTTP source URL before constructing
3. If the content is local, use a local stream/file API instead of ByteRangeDownloader

Example fix

// before
new ByteRangeDownloader(new Uri("pack://application:,,,/asset.xbap"), handle, timeout);
// after
new ByteRangeDownloader(new Uri("https://server/app/asset.xbap"), handle, timeout);

static bool IsHttpUri(Uri u) => u != null && !u.IsAbsoluteUri == false && (u.Scheme == Uri.UriSchemeHttp || u.Scheme == Uri.UriSchemeHttps);

static bool IsHttpUri(Uri? u) => u?.IsAbsoluteUri == true && (u.Scheme == Uri.UriSchemeHttp || u.Scheme == Uri.UriSchemeHttps);

try { var d = new ByteRangeDownloader(uri, handle, timeout); } catch (ArgumentException ex) when (ex.ParamName == "requestedUri") { /* fall back or log */ }

When it happens

Trigger: Calling the public ByteRangeDownloader constructor with a requestedUri whose Scheme is neither 'http' nor 'https' — typically a pack://, file://, or relative/resolved content URI.

Common situations: Developers hand a XAML package URI (pack://...) or a local file path URI to ByteRangeDownloader instead of the absolute remote HTTP URI backing the package.

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.UriNotAbsolute
• SR.UriNotAbsolute
• assembly
• Can only countersign parts with Digital Signature…
• Document PackagePart URI is not valid.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/393627e1bb197c08. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/MS/internal/IO/Packaging/ByteRangeDownloader.cs:404

        private void CheckDisposed()
        {
            if (_disposed)
            {
                throw new ObjectDisposedException(null, SR.ByteRangeDownloaderDisposed);
            }
        }

        /// <summary>
        /// Constructor for ByteRangeDownloader
        /// </summary>
        private ByteRangeDownloader(Uri requestedUri, SafeWaitHandle eventHandle)
        {
            ArgumentNullException.ThrowIfNull(requestedUri);

            // Ensure uri is correct scheme (http or https) Do case-sensitive comparison since Uri.Scheme contract is to return in lower case only.
            if (!string.Equals(requestedUri.Scheme, Uri.UriSchemeHttp, StringComparison.Ordinal) && !string.Equals(requestedUri.Scheme, Uri.UriSchemeHttps, StringComparison.Ordinal))
            {
                throw new ArgumentException(SR.InvalidScheme, nameof(requestedUri));
            }

            ArgumentNullException.ThrowIfNull(eventHandle);

            if (eventHandle.IsInvalid || eventHandle.IsClosed)
            {
                throw new ArgumentException(SR.InvalidEventHandle, nameof(eventHandle));
            }

            _requestedUri = requestedUri;
            _eventHandle = eventHandle;
        }

        /// <summary>
        /// Check if it has been errored out from the worker thread and re-throw the exception that was
        /// thrown from the worker thread
        /// </summary>
        /// <remarks>No need to lock in this function since the caller always locks before making this call</remarks>

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