dotnet/wpf · error · InvalidOperationException

Win32 edit control cannot have a child element.

Error message

Win32 edit control cannot have a child element.

What it means

WindowsEditBox implements ITextProvider but a Win32 edit control has no child elements, so ITextProvider.RangeFromChild always throws InvalidOperationException(EditControlsHaveNoChildren). Any childElement argument is by definition invalid for this control.

Solutions

1. Do not call RangeFromChild on edit-box TextPatterns; use DocumentRange/RangeFromPoint or selection ranges instead.
2. Guard by checking the element has children (FindFirstChild != null) before calling RangeFromChild.
3. Catch InvalidOperationException and treat the range as the document range.
4. For embedded objects, use a control that truly hosts children (e.g. rich text) rather than a Win32 edit box.

Example fix

// before
var range = textPattern.RangeFromChild(childElement); // always throws on edit boxes
// after
if (editBoxElement.FindFirstChild(TreeScope.Children, Condition.TrueCondition) == null)
{
    var range = textPattern.DocumentRange; // edit boxes have no children
}

var hasChildren = el.FindFirstChild(TreeScope.Children, Condition.TrueCondition) != null;
if (!hasChildren) { var range = textPattern.DocumentRange; }

try { return textPattern.RangeFromChild(child); }
catch (InvalidOperationException) { return textPattern.DocumentRange; }

When it happens

Trigger: Calling TextPattern.RangeFromChild with any IRawElementProviderSimple obtained under an edit box's automation element (e.g. from UIA tree traversal).

Common situations: Generic UIA traversal code that calls RangeFromChild for every TextPattern element without checking whether the element actually has children; frameworks that treat all TextPattern providers uniformly.

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

• The value of argument 'unit
• ' ' is not a valid value for this control.
• Character offset not valid in TextRange.
• new ArgumentNullException(name)
• Operation cannot be performed.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/82c0933f84607601. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/UIAutomation/UIAutomationClientSideProviders/MS/Internal/AutomationProxies/WindowsEditBox.cs:343

        ITextRangeProvider [] ITextProvider.GetSelection()
        {
            int start, end;
            GetSel(out start, out end);
            return new ITextRangeProvider[] { new WindowsEditBoxRange(this, start, end) };
        }

        ITextRangeProvider [] ITextProvider.GetVisibleRanges()
        {
            int start, end;
            GetVisibleRangePoints(out start, out end);

            return new ITextRangeProvider[] { new WindowsEditBoxRange(this, start, end) };
        }

        ITextRangeProvider ITextProvider.RangeFromChild(IRawElementProviderSimple childElement)
        {
            // we don't have any children so this call must be in error.
            throw new InvalidOperationException(SR.Format(SR.EditControlsHaveNoChildren, GetType().FullName));
        }

        ITextRangeProvider ITextProvider.RangeFromPoint(Point screenLocation)
        {
            // convert screen to client coordinates.
            // (Essentially ScreenToClient but MapWindowPoints accounts for window mirroring using WS_EX_LAYOUTRTL.)
            NativeMethods.Win32Point clientLocation = (NativeMethods.Win32Point)screenLocation;
            if (!Misc.MapWindowPoints(IntPtr.Zero, WindowHandle, ref clientLocation, 1))
            {
                return null;
            }

            // we have to deal with the possibility that the coordinate is inside the window rect
            // but outside the client rect. in that case we just scoot it over so it is at the nearest
            // point in the client rect.
            NativeMethods.Win32Rect clientRect = new NativeMethods.Win32Rect();
            if (!Misc.GetClientRect(WindowHandle, ref clientRect))
            {

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