dotnet/wpf · error · ArgumentException

SR.Animation_KeySpline_InvalidValue (controlPoint1)

Error message

SR.Animation_KeySpline_InvalidValue (controlPoint1)

What it means

This throw is the controlPoint2 branch of the same validation: the KeySpline(Point, Point) constructor rejects controlPoint2 when any of its X/Y coordinates is outside [0,1], raising ArgumentException with SR.Animation_KeySpline_InvalidValue and the parameter name 'controlPoint2'. Key spline control points must stay inside the unit square so the timing curve is monotone and bounded.

Solutions

Clamp controlPoint2's X and Y into [0,1] before constructing the KeySpline.
Check which parameter failed: the exception argument name tells you controlPoint2 is the offender; fix that value's units/range.
Pre-validate with a helper (both coords in 0..1) and log/repair bad config values.
Catch ArgumentException and substitute a linear default spline (0,0)/(1,1).

Example fix

// before
var spline = new KeySpline(new Point(0, 0), new Point(1.2, 0.9));
// after
var p2 = new Point(Math.Clamp(1.2, 0, 1), Math.Clamp(0.9, 0, 1)); // -> (1.0, 0.9)
var spline = new KeySpline(new Point(0, 0), p2);

Defensive patterns

Strategy: validation

Validate before calling

if (cp2.X < 0 || cp2.X > 1 || cp2.Y < 0 || cp2.Y > 1)
    cp2 = new Point(Math.Clamp(cp2.X, 0, 1), Math.Clamp(cp2.Y, 0, 1));
var spline = new KeySpline(cp1, cp2);

Type guard

static bool IsUnitPoint(Point p) => double.IsFinite(p.X) && double.IsFinite(p.Y) && p is { X: >= 0 and <= 1, Y: >= 0 and <= 1 };

Try / catch

try { spline = new KeySpline(cp1, cp2); }
catch (ArgumentException ex) when (ex.Message.Contains("controlPoint2"))
{
    spline = new KeySpline(cp1, new Point(1, 1));
}

Prevention

Read the exception's parameter name to see which control point is bad
Normalize percent-scaled config values by dividing by 100 before constructing
Clamp both points before the constructor call rather than one at a time
Add unit tests for spline parsing with out-of-range fixtures

When it happens

Trigger: new KeySpline(validCp1, cp2) where cp2.X or cp2.Y < 0.0 or > 1.0, e.g. new KeySpline(new Point(0,0), new Point(1.2, 0.9)).

Common situations: Same as the controlPoint1 case: percentages entered where fractions were expected, spline data loaded from external config/JSON, easing curves copied from other frameworks with different conventions.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/2a2a1fca2689553c. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Animation/KeySpline.cs:65

        /// <summary>
        /// Point constructor
        /// </summary>
        /// <param name="controlPoint1">the control point for the 0,0 endpoint</param>
        /// <param name="controlPoint2">the control point for the 1,1 endpoint</param>
        public KeySpline(Point controlPoint1, Point controlPoint2)
            : base()
        {
            if (!IsValidControlPoint(controlPoint1))
            {
                throw new ArgumentException(SR.Format(
                    SR.Animation_KeySpline_InvalidValue,
                    "controlPoint1",
                    controlPoint1));
            }

            if (!IsValidControlPoint(controlPoint2))
            {
                throw new ArgumentException(SR.Format(
                    SR.Animation_KeySpline_InvalidValue,
                    "controlPoint2",
                    controlPoint2));
            }

            _controlPoint1 = controlPoint1;
            _controlPoint2 = controlPoint2;

            _isDirty = true;
        }

        #endregion Constructors

        #region Freezable

        /// <summary>
        /// Implementation of <see cref="System.Windows.Freezable.CreateInstanceCore">Freezable.CreateInstanceCore</see>.
        /// </summary>

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