dotnet/wpf · error · ArgumentNullException

image.Source

Error message

image.Source

What it means

WpfPayload.AddImage throws ArgumentNullException named "image.Source" when the Image control handed to the payload has no Source set. A WPF payload image part needs an actual image source (URI/bitmap) to serialize into the package, so a Source-less Image is rejected.

Solutions

1. Set image.Source (e.g. new BitmapImage(new Uri(...))) before calling AddImage, and verify the URI resolves so Source is non-null.
2. Skip or placeholder images with null Source instead of adding them to the payload.
3. If Source loads asynchronously, wait for DownloadCompleted/DecodeFailed (or use the decoded BitmapSource directly) before adding.
4. Catch ArgumentNullException/ArgumentException and remove the offending image from the payload, logging a warning.

Example fix

// before
var image = new Image { Width = 100 }; // Source never set
wpfPayload.AddImage(image); // throws
// after
if (image.Source == null || string.IsNullOrEmpty(image.Source.ToString()))
    return null; // skip placeholder image
wpfPayload.AddImage(image);

if (image?.Source == null || string.IsNullOrEmpty(image.Source.ToString()))
    return null; // cannot serialize an image with no source

static bool HasUsableSource(Image image) =>
    image?.Source != null && !string.IsNullOrEmpty(image.Source.ToString());

try { wpfPayload.AddImage(image); }
catch (ArgumentNullException)
call image = PlaceholderImage(); /* or skip */ }

When it happens

Trigger: Constructing a new Image() (or one whose ImageSource failed to load, e.g. broken URI or failed download) and passing it to WpfPayload.AddImage while building an XAML/RTF payload for clipboard or document content.

Common situations: Images whose source URI 404'd or failed decode leaving Source null; dynamically created Image elements where the source is assigned asynchronously after AddImage runs; copy/paste code paths iterating a document containing placeholder images.

Related errors

• SR.WpfPayload_InvalidImageSource
• ' ' ContentType is not valid.
• annotation component
• ArgumentNullException
• ArgumentNullException(argName)

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/2644dbd15cb4190f. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Documents/WpfPayload.cs:484

            // Save encoded image data into the image part in the package
            Stream imageStream = imagePart.GetSeekableStream();
            using (imageStream)
            {
                bitmapEncoder.Save(imageStream);
            }
        }

        // Adds an image data to the package.
        // Returns a local Uri that must be used to access this data
        // from the package - from its top level directory.
        internal string AddImage(Image image)
        {
            ArgumentNullException.ThrowIfNull(image);

            if (image.Source == null)
            {
                throw new ArgumentNullException("image.Source");
            }

            if (string.IsNullOrEmpty(image.Source.ToString()))
            {
                throw new ArgumentException(SR.WpfPayload_InvalidImageSource);
            }

            if (_images == null)
            {
                _images = new List<Image>();
            }

            // Define the image uri for the new image
            string imagePartUriString = null;

            // Define image type
            string imageContentType = GetImageContentType(image.Source.ToString());

View on GitHub (pinned to 81131a70a4)