dotnet/wpf · error · InvalidOperationException

SR.DoesNotSupportMultipleSelection

Error message

SR.DoesNotSupportMultipleSelection

What it means

Win32 TreeView natively supports only single selection. AddToSelection is only valid when selection is not required and nothing is currently selected; otherwise the provider throws InvalidOperationException(SR.DoesNotSupportMultipleSelection).

Solutions

1. Use Select() instead of AddToSelection() to move the single selection to the item.
2. Check IsSelectionRequired and current selection before calling AddToSelection.
3. Use SelectionPattern/SelectionItemPattern only per the control's actual capabilities (query GetSupportedPatterns).
4. Catch InvalidOperationException and fall back to Select().

Example fix

// before
item.AddToSelection(); // TreeView is single-select
// after
if (item.Current.IsSelected) { /* already selected */ }
else item.Select();

bool canAdd = ((SelectionItemPattern)item.GetCurrentPattern(SelectionItemPattern.Pattern)).Current.IsSelectionRequired == false && treeView.FindAll(TreeScope.Children, SelectionPattern selectionCondition).Count == 0;

try { item.AddToSelection(); }
catch (InvalidOperationException) { item.Select(); } // single-select fallback

When it happens

Trigger: Calling SelectionItemPattern.AddToSelection() on a tree-view item when a selection already exists (GetSelection != IntPtr.Zero) or the container reports IsSelectionRequired == true — i.e. any attempt to create a second simultaneous selection.

Common situations: Tests written against multi-select assumptions (e.g. ported from ListBox/ListView multi-select UIs) applied to a standard single-select TreeView.

Related errors

• ElementNotAvailableException
• ElementNotEnabledException
• SR.OperationCannotBePerformed
• ' ' is not a valid value for this control.
• Element is not enabled.

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/80ceb8a967beb90f. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/UIAutomation/UIAutomationClientSideProviders/MS/Internal/AutomationProxies/WindowsTreeView.cs:1009

                }

                CheckForElementAvailable();

                // simple case: item already selected
                if (IsItemSelected())
                {
                    return;
                }

                IRawElementProviderSimple container = ((ISelectionItemProvider)this).SelectionContainer;
                bool selectionRequired = container != null ? ((ISelectionProvider)container).IsSelectionRequired : true;

                // For single selection containers that IsSelectionRequired == false and nothing is selected
                // an AddToSelection is valid.
                if (selectionRequired || WindowsTreeView.GetSelection(_hwnd) != IntPtr.Zero)
                {
                    // NOTE: TreeView do not natively support multiple selection
                    throw new InvalidOperationException(SR.DoesNotSupportMultipleSelection);
                }

                // Since nothing is selected try to select the item
                if (!WindowsTreeView.SelectItem(_hwnd, _hItem))
                {
                    throw new InvalidOperationException(SR.OperationCannotBePerformed);
                }
            }

            // Removes this element from the selection
            void ISelectionItemProvider.RemoveFromSelection ()
            {
                // Make sure that the control is enabled
                if (!SafeNativeMethods.IsWindowEnabled(_hwnd))
                {
                    throw new ElementNotEnabledException();
                }

View on GitHub (pinned to 81131a70a4)