dotnet/wpf · error · InvalidOperationException

SR.OperationCannotBePerformed

Error message

SR.OperationCannotBePerformed

What it means

GroupManagerCollection.GetManager (public) throws InvalidOperationException(SR.OperationCannotBePerformed) when a list-view HWND that is being queried has no group manager registered even though groups should exist - typically because the control transitioned out of a grouped mode (e.g. switching to List mode, which has no groups) and WinEvents for the removal were not delivered. The provider cannot hand back a valid manager and aborts with this sentinel exception. Comments again note the intended fix (RemoveGroupAndRaiseLogicalChangedEvent) was deferred.

Solutions

  1. Re-fetch the list element after the view-mode change so the provider re-registers group managers, then retry.
  2. Catch InvalidOperationException around UIA pattern calls and treat it as a signal the control's structure changed; invalidate cached children.
  3. Delay automation calls until after the ListView.View change completes (wait for the structure-changed event instead of polling immediately).
  4. If you own the app, switch view modes when no UIA clients are subscribed, or explicitly send a structure-changed notification after the change.

Example fix

// before
var item = cachedListElement.FindFirst(TreeScope.Children, nameCond);

// after
AutomationElement item;
try { item = cachedListElement.FindFirst(TreeScope.Children, nameCond); }
catch (InvalidOperationException)
{
    cachedListElement = ReFindList();   // refresh after a View change
    item = cachedListElement.FindFirst(TreeScope.Children, nameCond);
}
Defensive patterns

Strategy: try-catch

Validate before calling

if (list.FindAll(TreeScope.Children, groupCond).Count == 0) return null; // no groups to query

Type guard

bool HasGroups(AutomationElement list) => list.FindAll(TreeScope.Children, groupCond).Count > 0;

Try / catch

try { return GetManagerDependentCall(list); }
catch (InvalidOperationException) { list = RefindElement(hwnd); return GetManagerDependentCall(list); }

Prevention

When it happens

Trigger: Calling GetManager(hwnd) for a ListView whose view mode changed from a grouped mode (e.g. Details/Tile with groups) to List mode; the group manager was removed on the corresponding WinEvent but a lookup still arrives, or vice versa the reorder WinEvent was missed.

Common situations: UIA clients holding a cached ListView element while the user (or app code) changes ListView.View at runtime; grouped list views in Explorer-like UIs being toggled; test harnesses switching view modes mid-automation run.

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/7be533a5c27882f3. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/UIAutomation/UIAutomationClientSideProviders/MS/Internal/AutomationProxies/WindowsListViewGroupHelper.cs:61

        internal bool Contains(IntPtr hwnd)
        {
            return _groupManagers.ContainsKey(hwnd);
        }

        internal GroupManager this[IntPtr hwnd]
        {
            get
            {
                if (!WindowsListView.IsGroupViewEnabled(hwnd))
                {
                    // Group was disabled but we did not get the needed event
                    // since for some things events are not being sent
                    // (e.g: Going from some LV modes to - List mode, List mode does not have Groups)

                    // Microsoft - We may want to consider raising the event here
                    // The M7 work on checking if LE is valid however is the better way of going
                    // WindowsListView.RemoveGroupAndRaiseLogicalChangedEvent(_hwnd);
                    throw new InvalidOperationException(SR.OperationCannotBePerformed);
                }

                // The group may have been discarded by the reorder winevent.
                EnsureCreation (hwnd);

                GroupManager manager = _groupManagers[hwnd] as GroupManager;
                if (manager == null)
                {
                    // E.G. Going from the List mode to the something that has Group will cause this

                    // Microsoft- We may want to consider raising the event here
                    // The M7 work on checking if LE is valid however is the better way of going
                    // WindowsListView.RaiseLogicalChangedEvent(hwnd);
                    throw new InvalidOperationException(SR.OperationCannotBePerformed);
                }
                return manager;
            }
        }

View on GitHub (pinned to 81131a70a4)