dotnet/wpf · error · ArgumentException

Collection_CopyTo_ArrayCannotBeMultidimensional

Error message

Collection_CopyTo_ArrayCannotBeMultidimensional

What it means

ThousandthOfEmRealDoubles.CopyTo throws ArgumentException(SR.Collection_CopyTo_ArrayCannotBeMultidimensional) when the destination Array has Rank != 1. ICollection.CopyTo only supports single-dimensional arrays, matching the standard .NET collection contract.

Solutions

1. Pass a single-dimensional array (double[]) as the destination
2. If multidimensional storage is needed, copy into a flat double[] then index-map into the 2D array yourself
3. Add a Rank check before calling CopyTo

Example fix

// before
var dest = new double[count, 2];
collection.CopyTo(dest, 0);
// after
var dest = new double[count];
collection.CopyTo(dest, 0);

ArgumentNullException.ThrowIfNull(dest);
if (dest.Rank != 1) throw new ArgumentException("dest must be 1-D", nameof(dest));
collection.CopyTo(dest, index);

When it happens

Trigger: Calling CopyTo (or casting the collection to ICollection/ICollection<double> and calling CopyTo) with a multidimensional array such as double[,] as the destination.

Common situations: Passing a 2D array declared for grid-like storage to CopyTo; generic copy helpers that take Array instead of double[].

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

• Collection_CopyTo_ArrayCannotBeMultidimensional
• Collection_CopyTo_IndexGreaterThanOrEqualToArrayLength
• Collection_CopyTo_IndexGreaterThanOrEqualToArrayLength
• Collection_CopyTo_NumberOfElementsExceedsArrayLength
• SR.Collection_BadRank

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/5e835b81ee41ce9b. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/MS/internal/TextFormatting/ThousandthOfEmRealDoubles.cs:169

                {
                    _doubleList[i] = 0;
                }
            }
        }

        public bool Contains(double item)
        {
            return IndexOf(item) >= 0;
        }

        public void CopyTo(double[] array, int arrayIndex)
        {
            // parameter validations
            ArgumentNullException.ThrowIfNull(array);

            if (array.Rank != 1)
            {
                throw new ArgumentException(
                    SR.Collection_CopyTo_ArrayCannotBeMultidimensional, 
                    nameof(array));                
            }

            ArgumentOutOfRangeException.ThrowIfNegative(arrayIndex);

            if (arrayIndex >= array.Length)
            {
                throw new ArgumentException(
                    SR.Format(
                        SR.Collection_CopyTo_IndexGreaterThanOrEqualToArrayLength, 
                        "arrayIndex", 
                        "array"),
                    nameof(arrayIndex));
            }

            if ((array.Length - Count - arrayIndex) < 0)
            {

View on GitHub (pinned to 81131a70a4)