dotnet/wpf · error · ArgumentException

SR.Collection_BadRank

Error message

SR.Collection_BadRank

What it means

CopyTo validates the destination array before copying Typefaces into it. A multi-dimensional array (Rank != 1) cannot be used as an ICollection<T> copy target, so an ArgumentException with resource SR.Collection_BadRank is thrown.

Solutions

1. Allocate a one-dimensional Typeface[] whose length is at least the collection count
2. Convert any existing multi-dimensional array to a flat 1D array before copying

Example fix

// before
var arr = new Typeface[2, 2];
fontFamily.Typefaces.CopyTo(arr, 0);
// after
var arr = new Typeface[fontFamily.Typefaces.Count];
fontFamily.Typefaces.CopyTo(arr, 0);

if (array == null) throw new ArgumentNullException(nameof(array));
if (array.Rank != 1) throw new ArgumentException("1-D array required", nameof(array));
if (arrayIndex < 0 || arrayIndex >= array.Length) throw new ArgumentOutOfRangeException(nameof(arrayIndex));

When it happens

Trigger: Calling TypefaceCollection.CopyTo(array, index) where array was created as a multi-dimensional array, e.g. new Typeface[2,2].

Common situations: Passing rectangular arrays produced elsewhere in the code, or generic serialization code that allocates multi-dimensional buffers.

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_BadRank
• SR.Collection_BadRank
• SR.Collection_BadRank
• SR.CollectionNumberOfElementsMustBeGreaterThanZero
• SR.CollectionNumberOfElementsMustBeLessOrEqualTo

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/063fb40b1f5de6d6. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/MS/internal/FontFace/TypefaceCollection.cs:61

        }

        public bool Contains(Typeface item)
        {
            foreach (Typeface t in this)
            {
                if (t.Equals(item))
                    return true;
            }
            return false;
        }

        public void CopyTo(Typeface[] array, int arrayIndex)
        {
            ArgumentNullException.ThrowIfNull(array);

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

            // The extra "arrayIndex >= array.Length" check in because even if _collection.Count
            // is 0 the index is not allowed to be equal or greater than the length
            // (from the MSDN ICollection docs)
            ArgumentOutOfRangeException.ThrowIfNegative(arrayIndex);
            ArgumentOutOfRangeException.ThrowIfGreaterThanOrEqual(arrayIndex, array.Length);
            ArgumentOutOfRangeException.ThrowIfGreaterThan(arrayIndex, array.Length - Count);

            foreach (Typeface t in this)
            {
                array[arrayIndex++] = t;
            }
        }

        public int Count
        {
            get

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