dotnet/wpf · error · ArgumentException

SR.Collection_BadRank

Error message

SR.Collection_BadRank

What it means

BitmapSource.CriticalCopyPixels throws ArgumentException with SR.Collection_BadRank when the destination pixels array is multi-dimensional (Rank != 1). Pixel copy buffers must be a flat one-dimensional Array so bytes can be copied contiguously.

Solutions

  1. Allocate a flat 1D array (e.g. new int[width * height]) and pass that.
  2. Copy into the 1D buffer, then remap into the 2D array row by row afterwards.
  3. Overload-check: use the CopyPixels overload taking an IntPtr with stride if you must write into custom memory.

Example fix

// before
var pixels = new int[height, width];
bitmap.CopyPixels(pixels, stride, 0); // throws
// after
var pixels = new int[width * height];
bitmap.CopyPixels(pixels, width * 4, 0);
Defensive patterns

Strategy: validation

Validate before calling

if (pixels == null || pixels.Rank != 1)
    throw new ArgumentException("pixels must be a 1D array", nameof(pixels));

Type guard

bool IsFlatBuffer<T>(T[] buffer) => buffer != null; // use T[] not T[,]

Try / catch

try { bitmap.CopyPixels(pixels, stride, offset); } catch (ArgumentException ex) { /* flatten array */ }

Prevention

When it happens

Trigger: Calling bitmapSource.CopyPixels(pixels, ...) with a 2D array such as int[,] or Color[,] as the destination.

Common situations: Developers modeling image rows/columns with int[height,width] because it feels natural, then passing it directly to CopyPixels.

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

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/a5f3f8800923ade0. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Imaging/BitmapSource.cs:643

        }

        /// <summary>
        /// CriticalCopyPixels
        /// </summary>
        /// <param name="sourceRect"></param>
        /// <param name="pixels"></param>
        /// <param name="stride"></param>
        /// <param name="offset"></param>
        internal unsafe void CriticalCopyPixels(Int32Rect sourceRect, Array pixels, int stride, int offset)
        {
            ReadPreamble();
            _bitmapInit.EnsureInitializedComplete();
            CompleteDelayedCreation();

            ArgumentNullException.ThrowIfNull(pixels);

            if (pixels.Rank != 1)
                throw new ArgumentException(SR.Collection_BadRank, nameof(pixels));

            if (offset < 0)
            {
                HRESULT.Check((int)WinCodecErrors.WINCODEC_ERR_VALUEOVERFLOW);
            }

            int elementSize = -1;

            if (pixels is byte[])
                elementSize = 1;
            else if (pixels is short[] || pixels is ushort[])
                elementSize = 2;
            else if (pixels is int[] || pixels is uint[] || pixels is float[])
                elementSize = 4;
            else if (pixels is double[])
                elementSize = 8;

            if (elementSize == -1)

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