What causes "SR.InvalidStylusPointCollectionZeroCount" in dotnet/wpf?

Guard before constructing: only create a Stroke when stylusPoints.Count > 0

dotnet/wpf · error · ArgumentException

SR.InvalidStylusPointCollectionZeroCount

Error message

SR.InvalidStylusPointCollectionZeroCount

What it means

The internal Stroke constructor requires a StylusPointCollection with at least one point. An empty stroke has no geometry, bounds, or drawable path, so WPF rejects empty point collections at construction rather than creating a degenerate Stroke. ArgumentException is thrown naming the stylusPoints parameter.

Solutions

Guard before constructing: only create a Stroke when stylusPoints.Count > 0
If empty input is expected, skip stroke creation or use an empty StrokeCollection instead of an empty Stroke
Populate the StylusPointCollection with at least one StylusPoint before passing it in

Example fix

// before
var stroke = new Stroke(stylusPoints); // throws if empty
// after
if (stylusPoints.Count == 0) return null;
var stroke = new Stroke(stylusPoints);

Defensive patterns

Strategy: validation

Validate before calling

if (stylusPoints == null || stylusPoints.Count == 0) return null; // skip stroke creation

Type guard

bool IsValidStrokeSource(StylusPointCollection p) => p != null && p.Count > 0;

Try / catch

try { var stroke = new Stroke(stylusPoints); } catch (ArgumentException ex) when (ex.ParamName == "stylusPoints") { /* handle empty collection */ }

Prevention

Never construct strokes from potentially empty captured point lists
Represent absence of ink with an empty StrokeCollection, not an empty Stroke
Assert non-empty point data when deserializing persisted ink

When it happens

Trigger: Calling any public Stroke constructor (Stroke(StylusPointCollection), Stroke(StylusPointCollection, DrawingAttributes)) with a StylusPointCollection whose Count == 0, e.g. new Stroke(new StylusPointCollection()).

Common situations: Building strokes programmatically from captured stylus data that produced no samples; converting persisted ink where a stroke's point list was empty; test fixtures constructing default strokes.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/17fbc8b08ef23600. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Ink/Stroke.cs:50

        /// <param name="stylusPoints">StylusPointCollection that makes up the stroke</param>
        /// <param name="drawingAttributes">drawingAttributes</param>
        public Stroke(StylusPointCollection stylusPoints, DrawingAttributes drawingAttributes)
            : this(stylusPoints, drawingAttributes, null)
        {
        }

        /// <summary>Create a stroke from a StylusPointCollection</summary>
        /// <remarks>
        /// </remarks>
        /// <param name="stylusPoints">StylusPointCollection that makes up the stroke</param>
        /// <param name="drawingAttributes">drawingAttributes</param>
        /// <param name="extendedProperties">extendedProperties</param>
        internal Stroke(StylusPointCollection stylusPoints, DrawingAttributes drawingAttributes, ExtendedPropertyCollection extendedProperties)
        {
            ArgumentNullException.ThrowIfNull(stylusPoints);
            if (stylusPoints.Count == 0)
            {
                throw new ArgumentException(SR.InvalidStylusPointCollectionZeroCount, nameof(stylusPoints));
            }
            ArgumentNullException.ThrowIfNull(drawingAttributes);

            _drawingAttributes = drawingAttributes;
            _stylusPoints = stylusPoints;
            _extendedProperties = extendedProperties;

            Initialize();
        }

        /// <summary>
        /// Internal helper to set up listeners, called by ctor and by Clone
        /// </summary>
        private void Initialize()
        {
            _drawingAttributes.AttributeChanged += new PropertyDataChangedEventHandler(DrawingAttributes_Changed);
            _stylusPoints.Changed += new EventHandler(StylusPoints_Changed);
            _stylusPoints.CountGoingToZero += new CancelEventHandler(StylusPoints_CountGoingToZero);

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