stride3d/stride · error · NotSupportedException

This operation is not supported.

Error message

This operation is not supported.

What it means

EditorGameEntitySelectionService subscribes to selection collection changes and only supports Add/Remove/Reset actions; Replace or Move notifications on the selection collection are explicitly unsupported and throw NotSupportedException.

Solutions

1. Replace item replacement with explicit Remove + Add calls
2. Replace Move with Remove at old index followed by Insert at new index
3. Clear the collection and re-add the desired selection (maps to supported Reset)
4. Wrap any mass-selection mutation in Remove/Add sequences

Example fix

// before
selectedItems[0] = newItem;               // Replace -> throws
// after
selectedItems.RemoveAt(0);
selectedItems.Insert(0, newItem);          // supported Add/Remove

if (action == NotifyCollectionChangedAction.Replace || action == NotifyCollectionChangedAction.Move)
    throw new NotSupportedException("Mutate the selection via Add/Remove/Clear only");

try { ApplySelectionChange(e); }
catch (NotSupportedException ex) { log.Warn(ex); RebuildSelectionFromSnapshot(); }

When it happens

Trigger: Calling ObservableCollection.Move or replacing an item via the indexer (list[i] = x) on the selection collection the service monitors; any API that raises NotifyCollectionChangedAction.Replace or .Move.

Common situations: Custom tooling bulk-editing the selection by index replacement; data binding frameworks that replace items instead of removing/adding; third-party code assuming all collection mutations are allowed.

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

• This operation is not supported by the source tracker.
• An item with the same key has already been added.
• The given key was not present in the dictionary.
• Internal error, the collection has already muted to a…
• The given item does not validate the collection constraint.

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/e605a20feca51e19. Report an issue: GitHub.

Appendix: source

Thrown at sources/editor/Stride.Assets.Presentation/AssetEditors/EntityHierarchyEditor/Game/EditorGameEntitySelectionService.cs:392

                        break;
                    case NotifyCollectionChangedAction.Remove:
                        foreach (EntityHierarchyItemViewModel oldItem in e.OldItems)
                        {
                            var root = oldItem as SceneRootViewModel;
                            if (root != null)
                                RemoveFromSelection(root);
                            else
                                foreach (var entity in oldItem.InnerSubEntities)
                                    RemoveFromSelection(entity);
                        }
                        break;
                    case NotifyCollectionChangedAction.Reset:
                        SelectedIds.Clear();
                        SelectedRootIds.Clear();
                        break;
                    case NotifyCollectionChangedAction.Replace:
                    case NotifyCollectionChangedAction.Move:
                        throw new NotSupportedException("This operation is not supported.");
                    default:
                        throw new ArgumentOutOfRangeException();
                }

                RaiseSelectionUpdated(oldSelectionIds);
            }
        }

        private void RaiseSelectionUpdated(IReadOnlyCollection<AbsoluteId> oldSelectionIds)
        {
            var newSelectionIds = GetSelectedRootIds();
            Editor.Controller.InvokeAsync(() =>
            {
                var oldSelection = oldSelectionIds.Select(x => Editor.Controller.FindGameSidePart(x)).Cast<Entity>().NotNull().ToList();
                var newSelection = newSelectionIds.Select(x => Editor.Controller.FindGameSidePart(x)).Cast<Entity>().NotNull().ToList();
                SelectionUpdated?.Invoke(this, new EntitySelectionEventArgs(oldSelection, newSelection));
            });
        }

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