dotnet/wpf · error · ArgumentException

SR.TextRange_UnsupportedDataFormat (dataFormat)

Error message

SR.TextRange_UnsupportedDataFormat (dataFormat)

What it means

TextRangeBase.Save throws ArgumentException when the dataFormat string passed for saving the range content is not one of the supported formats (DataFormats.Xaml, XamlPackage, Rtf). The message includes the unsupported format name. This guards the serialization switch in the Save path.

Solutions

1. Use only "Xaml", "XamlPackage", or "Rtf" (DataFormats.Xaml / DataFormats.XamlPackage / DataFormats.Rtf) with TextRange.Save
2. For plain text, extract range.Text and write it yourself
3. Validate the format string against the supported list before calling

Example fix

// before
range.Save(stream, DataFormats.Text);
// after
range.Save(stream, DataFormats.Xaml);

var supported = new[]{ DataFormats.Xaml, DataFormats.XamlPackage, DataFormats.Rtf };
if (!supported.Contains(dataFormat)) throw new NotSupportedException(dataFormat);

bool IsSaveableFormat(string f) => f is DataFormats.Xaml or DataFormats.XamlPackage or DataFormats.Rtf;

try { range.Save(stream, dataFormat); } catch (ArgumentException ex) { /* unsupported save format */ }

When it happens

Trigger: Calling TextRange.Save(stream, dataFormat) with formats like DataFormats.Text, Html, or custom strings — the Save path only writes Xaml, XamlPackage, and Rtf.

Common situations: Assuming Save supports the same formats as Load/Clipboard; passing DataFormats.UnicodeText or Html expecting plain/HTML output; programmatic export code with a typo in the format string.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• ArgumentNullException(nameof(writer))
• ArgumentOutOfRangeException(routedEvent)
• Cannot find the appropriate serializer.
• Cannot find the appropriate serializer.
• Cannot find the appropriate serializer.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/de47fe25433f33dd. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Documents/TextRangeBase.cs:1538

                // independently whether there are images in it or not.
                WpfPayload.SaveRange(thisRange, ref stream, /*useFlowDocumentAsRoot:*/false, preserveTextElements);
            }
            else if (dataFormat == DataFormats.Rtf)
            {
                Stream wpfPayloadMemory = null;
                // Passing null as a wpfPayloadStream we allow to not create wpf package
                // when it is not needed (there is no images in the range)
                string xamlText = WpfPayload.SaveRange(thisRange, ref wpfPayloadMemory, /*useFlowDocumentAsRoot:*/false);
                // Convert xaml to rtf text to set rtf data into data object.
                string rtfText = TextEditorCopyPaste.ConvertXamlToRtf(xamlText, wpfPayloadMemory);
                StreamWriter rtfStreamWriter = new StreamWriter(stream);
                rtfStreamWriter.Write(rtfText);
                rtfStreamWriter.Flush();
            }
            else
            {
                // Unsupported format - thows exception
                throw new ArgumentException(SR.Format(SR.TextRange_UnsupportedDataFormat, dataFormat), nameof(dataFormat));
            }
        }

        internal static void Load(TextRange thisRange, Stream stream, string dataFormat)
        {
            ArgumentNullException.ThrowIfNull(stream);
            ArgumentNullException.ThrowIfNull(dataFormat);

            NormalizeRange(thisRange);

            // Reset the stream position to the beginning
            if (stream.CanSeek)
            {
                stream.Seek(0, SeekOrigin.Begin);
            }

            if (dataFormat == DataFormats.Text)
            {

View on GitHub (pinned to 81131a70a4)