dotnet/wpf · error · ArgumentOutOfRangeException

SR.Visual_ArgumentOutOfRange

Error message

SR.Visual_ArgumentOutOfRange

What it means

AccessText.GetVisualChild overrides FrameworkElement's visual-child accessor; AccessText has exactly one visual child (its internal TextBlock). Any index other than 0 throws this ArgumentOutOfRangeException, which normally indicates a bug in visual-tree walking code rather than a caller mistake in normal usage.

Solutions

1. Use VisualTreeHelper.GetChild(accessText, i) only for i in [0, VisualTreeHelper.GetChildrenCount(accessText)-1].
2. Access the inner text via accessText.Text instead of digging into the visual child.
3. Fix enumeration code that iterates beyond the child count.

Example fix

// before
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
    var v = VisualTreeHelper.GetChild(accessText, i); // may exceed
// after
int n = VisualTreeHelper.GetChildrenCount(accessText);
for (int i = 0; i < n; i++)
    var v = VisualTreeHelper.GetChild(accessText, i);

int count = VisualTreeHelper.GetChildrenCount(accessText);
for (int i = 0; i < count; i++) { var child = VisualTreeHelper.GetChild(accessText, i); }

bool HasVisualChild(AccessText at, int i) => i >= 0 && i < VisualTreeHelper.GetChildrenCount(at);

try { var v = VisualTreeHelper.GetChild(accessText, i); } catch (ArgumentOutOfRangeException) { /* i out of range: AccessText has only one visual child */ }

When it happens

Trigger: Calling GetVisualChild(1) or higher; iterating with VisualTreeHelper.GetChild using a count obtained from a different element; custom code assuming AccessText has multiple visual children.

Common situations: Custom hit-testing or visual-tree enumeration loops with off-by-one bounds (using VisualChildrenCount of the parent, not the child).

Related errors

• Specified index is out of range or child at index is null…
• Specified index is out of range or child at index is null…
• SR.Visual_ArgumentOutOfRange
• SR.Visual_ArgumentOutOfRange
• SR.Visual_ArgumentOutOfRange

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/9fb91c9ea40e4e17. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/AccessText.cs:533

            InitializeTextContainerListener();
        }

        /// <summary>
        /// Gets the Visual children count of the AccessText control.
        /// </summary>
        protected override int VisualChildrenCount
        {
            get { return 1; }
        }

        /// <summary>
        /// Gets the Visual child at the specified index.
        /// </summary>
        protected override Visual GetVisualChild(int index)
        {
            if (index != 0)
            {
                throw new ArgumentOutOfRangeException(nameof(index), index, SR.Visual_ArgumentOutOfRange); 
            }
            return TextBlock;
        }

        // Provides custom serialization for this element
        internal static void SerializeCustom(XmlWriter xmlWriter, object o)
        {
            Run inlineScope = o as Run;
            if (inlineScope != null)
            {
                xmlWriter.WriteString(AccessKeyMarker + inlineScope.Text);
            }
        }

        private static Style AccessKeyStyle
        {
            get
            {

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