dotnet/wpf · warning · InvalidOperationException

Microsoft.Windows.Controls.SR.UIA_OperationCannotBePerformed

Error message

Microsoft.Windows.Controls.SR.UIA_OperationCannotBePerformed

What it means

Inside IExpandCollapseProvider.Expand, the peer has realized the RibbonMenuItem but verifies the item can actually expand: its Role must be TopLevelHeader or SubmenuHeader and it must have items. A leaf menu item (or an empty header) cannot expand, so the peer throws InvalidOperationException with SR.UIA_OperationCannotBePerformed.

Solutions

Only call Expand on menu items that act as headers with children; check the item's role/items first via the RibbonMenuItem API or the automation tree.
Read ExpandCollapseState instead of calling Expand for leaf items - they are always Collapsed and not expandable.
Catch InvalidOperationException around Expand and treat it as 'item has no submenu'.
Restructure ribbon data so header items always contain items if expandability is expected.

Example fix

// before
expandCollapsePattern.Expand();
// after
if (menuItem.HasItems && (menuItem.Role == MenuItemRole.TopLevelHeader || menuItem.Role == MenuItemRole.SubmenuHeader))
    expandCollapsePattern.Expand();

Defensive patterns

Strategy: validation

Validate before calling

bool canExpand = menuItem.HasItems && (menuItem.Role == MenuItemRole.TopLevelHeader || menuItem.Role == MenuItemRole.SubmenuHeader);

Type guard

var header = owner as RibbonMenuItem; if (header != null && header.HasItems && header.HasItems) { /* expandable */ }

Prevention

Check Role and HasItems before Expand
Read ExpandCollapseState for leaf items instead of expanding them
Skip non-header items in automation sweeps

When it happens

Trigger: Calling Expand() on a RibbonMenuItem whose MenuItemRole is TopLevelItem or SubmenuItem (no submenu), or on a header item whose HasItems is false.

Common situations: Test suites iterating all ribbon menu items and calling Expand on each; applications where ribbon categories contain only leaf items so headers have no children.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/97b1c7402dc7f94e. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/System.Windows.Controls.Ribbon/Microsoft/Windows/Automation/Peers/RibbonMenuItemDataAutomationPeer.cs:151

        {
            if (!IsEnabled())
                throw new ElementNotEnabledException();

            UIElement owner = GetWrapper();
            if (owner == null)
            {
                throw new ElementNotAvailableException(Microsoft.Windows.Controls.SR.VirtualizedElement);
            }

            RibbonMenuItem menuItemOwner = owner as RibbonMenuItem;
            if (menuItemOwner != null)
            {
                MenuItemRole role = menuItemOwner.Role;

                if ((role != MenuItemRole.TopLevelHeader && role != MenuItemRole.SubmenuHeader)
                    || !menuItemOwner.HasItems)
                {
                    throw new InvalidOperationException(Microsoft.Windows.Controls.SR.UIA_OperationCannotBePerformed);
                }

                menuItemOwner.IsSubmenuOpen = true;
            }
            else
            {
                throw new InvalidOperationException(Microsoft.Windows.Controls.SR.UIA_OperationCannotBePerformed);
            }
        }

        ///
        void IExpandCollapseProvider.Collapse()
        {
            if (!IsEnabled())
                throw new ElementNotEnabledException();

            UIElement owner = GetWrapper();
            if (owner == null)

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