dotnet/wpf · error · ArgumentException

SR.Size_HeightCannotBeNegative

Error message

SR.Size_HeightCannotBeNegative

What it means

Rect.Height's setter validates the assigned value is non-negative and throws ArgumentException otherwise. Heights are magnitudes in WPF geometry; negative values indicate a computation bug (e.g. bottom computed above top) and are rejected to keep layout math well-defined.

Solutions

1. Clamp: rect.Height = Math.Max(0, computedHeight).
2. Normalize with Math.Abs(bottom - top) or use the Rect(Point, Point) constructor that swaps points as needed.
3. Fix the upstream coordinate computation so bottom/top are ordered before deriving height.

Example fix

// before
rect.Height = bottom - rect.Y; // ArgumentException when dragged up
// after
var top = Math.Min(rect.Y, bottom);
rect.Y = top;
rect.Height = Math.Abs(bottom - top);

if (newHeight >= 0 && !rect.IsEmpty) { rect.Height = newHeight; }

static bool IsValidHeight(double h) => !double.IsNaN(h) && h >= 0;

try { rect.Height = h; }
catch (ArgumentException) { rect.Height = Math.Max(0, h); }

When it happens

Trigger: Assigning rect.Height = value where value < 0 — commonly from bottom - top with swapped coordinates, or a scaled/animated value that transiently dips below zero.

Common situations: Drag-resize handling that doesn't account for dragging above/upward; zoom or scale transforms producing negative extents; parsing external data with negative extents.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

• SR.Size_WidthCannotBeNegative
• SR.Size_WidthAndHeightCannotBeNegative
• ' ' is not a valid value for ' '.
• ArgumentException(message, name)
• ArgumentNullException(name)

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/84f3d4683392e9b8. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsBase/System/Windows/Rect.cs:277

        /// be negative if this is the empty rectangle, in which case it will be negative infinity.
        /// If this rect is Empty, setting this property is illegal.
        /// </summary>
        public double Height
        {
            get
            {
                return _height;
            }
            set
            {
                if (IsEmpty)
                {
                    throw new System.InvalidOperationException(SR.Rect_CannotModifyEmptyRect);
                }

                if (value < 0)
                {
                    throw new System.ArgumentException(SR.Size_HeightCannotBeNegative);
                }

                _height = value;
            }
        }

        /// <summary>
        /// Left Property - This is a read-only alias for X
        /// If this is the empty rectangle, the value will be positive infinity.
        /// </summary>
        public double Left
        {
            get
            {
                return _x;
            }
        }

View on GitHub (pinned to 81131a70a4)