dotnet/wpf · error · ArgumentException

SR.Cursor_UnsupportedFormat (cursorFile)

Error message

SR.Cursor_UnsupportedFormat (cursorFile)

What it means

The Cursor(string cursorFile) constructor requires the file to have a .cur or .ani extension (checked before LoadFromFile); any other extension throws ArgumentException (SR.Cursor_UnsupportedFormat) with the offending file name.

Solutions

1. Convert the image to a genuine .cur or .ani file and pass that path.
2. Validate the extension with Path.GetExtension before constructing and show a clear user-facing message.
3. Ship known-good .cur/.ani assets as resources and load via Application.GetResourceStream instead of arbitrary files.

Example fix

// before
var cursor = new Cursor(cursorPath); // cursorPath = "spinner.png"
// after
if (Path.GetExtension(cursorPath) is ".cur" or ".ani")
    var cursor = new Cursor(cursorPath);
else
    throw new InvalidOperationException($"Cursor file must be .cur or .ani: {cursorPath}");

var ext = Path.GetExtension(cursorFile);
if (ext.Equals(".cur", StringComparison.OrdinalIgnoreCase) || ext.Equals(".ani", StringComparison.OrdinalIgnoreCase))
    this.Cursor = new Cursor(cursorFile);

static bool IsCursorFile(string p) => ".cur".Equals(Path.GetExtension(p), StringComparison.OrdinalIgnoreCase) || ".ani".Equals(Path.GetExtension(p), StringComparison.OrdinalIgnoreCase);

try { this.Cursor = new Cursor(cursorFile); } catch (ArgumentException ex) { /* fallback to Cursors.Arrow and report unsupported format */ }

When it happens

Trigger: new Cursor(@"C:\icons\spinner.png"), new Cursor("pointer.svg"), or a path with no extension — anything not ending in .cur or .ani.

Common situations: Pointing the app at downloaded or design-team cursor assets in PNG/SVG/GIF format, or paths whose extension was stripped by a config transform.

Related errors

• Document does not contain a package.
• Document does not contain any rights management-protected…
• FileFormatException
• Image_CantDealWithStream
• Image_CantDealWithUri

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/415481503921f154. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/Cursor.cs:63

        /// Cursor from .ani or .cur file
        /// </summary>
        /// <param name="cursorFile"></param>
        /// <param name="scaleWithDpi"></param>
        public Cursor(string cursorFile, bool scaleWithDpi)
        {
            _scaleWithDpi = scaleWithDpi;
            ArgumentNullException.ThrowIfNull(cursorFile);

            if ((cursorFile != String.Empty) &&
                (cursorFile.EndsWith(".cur", StringComparison.OrdinalIgnoreCase) ||
                 cursorFile.EndsWith(".ani", StringComparison.OrdinalIgnoreCase)))
            {
                LoadFromFile(cursorFile);
                _fileName = cursorFile;
            }
            else
            {
                throw new ArgumentException(SR.Format(SR.Cursor_UnsupportedFormat , cursorFile));
            }
        }

        /// <summary>
        /// Cursor from Stream
        /// </summary>
        /// <param name="cursorStream"></param>
        public Cursor(Stream cursorStream):this(cursorStream, false)
        {
        }

        /// <summary>
        /// Cursor from Stream
        /// </summary>
        /// <param name="cursorStream"></param>
        /// <param name="scaleWithDpi"></param>
        public Cursor(Stream cursorStream, bool scaleWithDpi)
        {

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