dotnet/wpf · error · NotSupportedException

SR.RangeActionsNotSupported

Error message

SR.RangeActionsNotSupported

What it means

Selector only supports single-item Add operations on SelectedItems. OnSelectedItemsCollectionChanged throws NotSupportedException when a NotifyCollectionChangedAction.Add event carries more than one new item (a range add), because Selector's SelectionChange logic resolves one item at a time. Range mutations of SelectedItems are explicitly unsupported by the WPF Selector API.

Solutions

  1. Add one item at a time in a loop: foreach (var i in items) listBox.SelectedItems.Add(i);
  2. Replace the whole selection with SelectionMode change plus individual IsSelected=true on each item container
  3. Use ListCollectionView-free plain ListBox APIs: set each ItemContainerStyle binding to IsSelected

Example fix

// before
listBox.SelectedItems.AddRange(newItems); // range add -> throws
// after
foreach (var item in newItems)
    listBox.SelectedItems.Add(item);
Defensive patterns

Strategy: validation

Validate before calling

if (items.Count > 1)
    throw new NotSupportedException("Selector.SelectedItems supports single-item Add only.");

Try / catch

try
{
    listBox.SelectedItems.Add(item);
}
catch (NotSupportedException ex)
{
    // add items one by one instead
}

Prevention

When it happens

Trigger: Calling SelectedItems.AddRange or inserting multiple items at once; a custom ObservableCollection<T> derived from SelectedItems' type that fires a bulk Add; any wrapper collection raising Add with NewItems.Count != 1.

Common situations: Replacing SelectedItems with a custom collection type that batches changes; bulk-binding code that adds several selected items in one call; framework version differences where bulk Add worked with another collection.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/41a763a82f9b29eb. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/Primitives/Selector.cs:873

            if (SelectionChange.IsActive)
            {
                return;
            }

            if (!CanSelectMultiple)
            {
                throw new InvalidOperationException(SR.ChangingCollectionNotSupported);
            }

            SelectionChange.Begin();
            bool succeeded=false;
            try
            {
                switch (e.Action)
                {
                    case NotifyCollectionChangedAction.Add:
                        if (e.NewItems.Count != 1)
                            throw new NotSupportedException(SR.RangeActionsNotSupported);

                        SelectionChange.Select(NewUnresolvedItemInfo(e.NewItems[0]), false /* assumeInItemsCollection */);
                        break;

                    case NotifyCollectionChangedAction.Remove:
                        if (e.OldItems.Count != 1)
                            throw new NotSupportedException(SR.RangeActionsNotSupported);

                        SelectionChange.Unselect(NewUnresolvedItemInfo(e.OldItems[0]));
                        break;

                    case NotifyCollectionChangedAction.Reset:
                        SelectionChange.CleanupDeferSelection();
                        for (int i = 0; i < _selectedItems.Count; i++)
                        {
                            SelectionChange.Unselect(_selectedItems[i]);
                        }

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