microsoft/autogen · error · ArgumentOutOfRangeException

Specified argument was out of the range of valid values. (Pa

Error message

Specified argument was out of the range of valid values. (Parameter 'arrayIndex')

What it means

Bounds check in ICollection<AIContent>.CopyTo: arrayIndex must satisfy 0 <= arrayIndex < array.Length, otherwise ArgumentOutOfRangeException(nameof(arrayIndex)). Note it rejects arrayIndex == array.Length even for an empty collection, which is slightly stricter than some BCL implementations.

Source

Thrown at dotnet/src/Microsoft.AutoGen/AgentChat/Abstractions/Messages.cs:326

    }

    /// <inheritdoc cref="ICollection{AIContent}.Contains" />
    public bool Contains(AIContent item)
    {
        return this.Content.Any(x => x.AIContent == item);
    }

    /// <inheritdoc cref="ICollection{AIContent}.CopyTo" />
    public void CopyTo(AIContent[] array, int arrayIndex)
    {
        if (array == null)
        {
            throw new ArgumentNullException(nameof(array));
        }

        if (arrayIndex < 0 || arrayIndex >= array.Length)
        {
            throw new ArgumentOutOfRangeException(nameof(arrayIndex));
        }

        if (array.Length - arrayIndex < this.Content.Count)
        {
            throw new ArgumentException("The number of elements in the source is greater than the available space from arrayIndex to the end of the destination array.");
        }

        for (var i = 0; i < this.Content.Count; i++)
        {
            array[arrayIndex + i] = this.Content[i].AIContent;
        }
    }

    /// <inheritdoc cref="IEnumerable{AIContent}.GetEnumerator" />
    public IEnumerator<AIContent> GetEnumerator()
    {
        return this.Content.Select(x => x.AIContent).GetEnumerator();
    }

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Pass an index strictly inside the array: 0 <= arrayIndex < array.Length (use the count of already-filled elements, not array.Length)
2. Ensure the destination array is non-empty; skip CopyTo entirely when there is nothing to copy
3. Double-check offset arithmetic when copying multiple collections into one buffer

Example fix

// before
msg.Content.CopyTo(dest, dest.Length); // always out of range
// after
msg.Content.CopyTo(dest, filled); // filled = number of elements already written

if (arrayIndex < 0 || arrayIndex >= array.Length) throw new ArgumentOutOfRangeException(nameof(arrayIndex), "must be 0 <= index < length");
msg.Content.CopyTo(array, arrayIndex);

When it happens

Trigger: Calling CopyTo(array, negativeIndex) or CopyTo(array, array.Length) (e.g. appending after existing items but passing length instead of a valid last index), or on an empty/zero-length array where any index fails.

Common situations: Index arithmetic bugs when copying into a larger buffer at an offset; passing array.Length by mistake when the intent was 'end of data so far'; zero-length arrays from empty allocations.

Related errors

• Value cannot be null. (Parameter 'array')
• The number of elements in the source is greater than the ava
• The recent update is not a TextMessage
• The content has more than one choice. Please try another inp
• Invalid ChatResponseMessage

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/32a7bf2a85a2ff47. Report an issue: GitHub.