dotnet/wpf · error · InvalidDataException

SR.DocumentStreamMustBeXpsFile

Error message

SR.DocumentStreamMustBeXpsFile

What it means

ThrowIfInvalidXpsFileForSave throws InvalidDataException when the target file's extension is not .xps (case-insensitive comparison against XpsFileExtension). Save operations require the destination to be an XPS file; saving to a non-XPS extension would produce an incorrectly named package.

Solutions

1. Ensure the save target path ends with the .xps extension before initiating the save.
2. When generating temp file names, append .xps (e.g. Path.ChangeExtension(path, ".xps")).
3. Validate user-supplied file names in the save dialog and correct/append the extension.

Example fix

// before
var path = Path.Combine(tempDir, Guid.NewGuid().ToString()); // no extension
// after
var path = Path.ChangeExtension(Path.Combine(tempDir, Guid.NewGuid().ToString()), ".xps");

bool isXpsTarget = string.Equals(Path.GetExtension(location.LocalPath), ".xps", StringComparison.OrdinalIgnoreCase);

try { SaveTo(location); }
catch (InvalidDataException) { location = new Uri(Path.ChangeExtension(location.LocalPath, ".xps")); SaveTo(location); }

When it happens

Trigger: Save/commit flows (Copy, SwapWithOriginal, MakeTempFile) given a location URI whose LocalPath extension is not '.xps', e.g. '.zip', '.oxps', or a no-extension temp name.

Common situations: Users typing a filename with a wrong or missing extension in a Save dialog; code generating temp file names without appending .xps; renaming documents to .zip to inspect contents then trying to save back.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• " }} " element found. Expected fixed page element ( }} ).
• ' ' ContentType is not valid.
• ' ' ContentType is not valid.
• Buffer address passed to GetText cannot be NULL.
• Cannot access the stream after it is closed.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/11729e51e437a12f. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationUI/MS/Internal/Documents/Application/DocumentStream.cs:958

                e);
        }            
    }

    /// <summary>
    /// Will throw if location is not a XpsDocument file.
    /// </summary>
    /// <exception cref="System.ArgumentNullException"/>
    /// <exception cref="System.InvalidOperationException"/>
    /// <exception cref="System.InvalidDataException"/>
    /// <param name="location"></param>
    private static void ThrowIfInvalidXpsFileForSave(Uri location)
    {
        ThrowIfInvalidXpsFileForOpen(location);

        if (!Path.GetExtension(location.LocalPath).Equals(
            XpsFileExtension, StringComparison.OrdinalIgnoreCase))
        {
            throw new InvalidDataException(
                SR.DocumentStreamMustBeXpsFile);
        }
    }

    /// <summary>
    /// Will throw if location is not a valid file.
    /// </summary>
    /// <exception cref="System.ArgumentNullException"/>
    /// <exception cref="System.InvalidOperationException"/>
    private static void ThrowIfInvalidXpsFileForOpen(Uri location)
    {
        ArgumentNullException.ThrowIfNull(location);
        if (!location.IsFile)
        {
            throw new InvalidOperationException(
                SR.DocumentStreamMustBeFileSource);
        }
    }

View on GitHub (pinned to 81131a70a4)