stride3d/stride · error · InvalidOperationException

parent cannot be null

Error message

parent cannot be null

What it means

Inside EntityFolderViewModel.UpdateName (called from the Name setter), each contained entity's Folder design property is updated from its view-model parent; a null cast parent means the entity's view-model tree is inconsistent, so an InvalidOperationException is thrown rather than writing a wrong folder path.

Solutions

1. Fix the view-model tree so every entity in InnerSubEntities has a non-null parent
2. Remove/re-attach orphaned entities before renaming the folder
3. Inspect entity.Parent in the debugger to find the inconsistent node

Example fix

// before
folder.Name = newName; // throws if an entity has null parent
// after
foreach (var e in folder.InnerSubEntities)
    if (e.Parent == null) throw new InvalidOperationException($"Entity {e.Name} is not attached");
folder.Name = newName;

bool canRename = folder.InnerSubEntities.All(e => e.Parent != null);
if (canRename) folder.Name = newName;

try { folder.Name = newName; }
catch (InvalidOperationException ex) { /* repair inconsistent entity tree */ }

When it happens

Trigger: Renaming a folder when one of its InnerSubEntities has a null Parent view-model (entity attached to folder but not to a parent node in the view-model tree).

Common situations: Hierarchy partially built or modified concurrently; entities reparented outside the transaction system before the rename.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• is not contained in a hierarchy.
• Entity shouldn't have a parent.
• IsObjectReference returned true for an object that is not…
• and cannot both be empty.
• Internal error, the collection has already muted to a…

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/ddeb203fcdf62ade. Report an issue: GitHub.

Appendix: source

Thrown at sources/editor/Stride.Assets.Presentation/AssetEditors/EntityHierarchyEditor/ViewModels/EntityFolderViewModel.cs:195

            if (Editor.UndoRedoService.UndoRedoInProgress)
            {
                name = newName;
                return;
            }

            using (var transaction = Editor.UndoRedoService.CreateTransaction())
            {
                // We need to update the name first so that the Path properties is consistent
                var oldName = name;
                name = newName;

                foreach (var entity in InnerSubEntities)
                {
                    var node = Editor.NodeContainer.GetOrCreateNode(entity.EntityDesign);
                    // In this case, the parent is either the current folder or a subfolder in between
                    var parent = (EntityFolderViewModel)entity.Parent;
                    if (parent == null) throw new InvalidOperationException($"{nameof(parent)} cannot be null");
                    node[nameof(EntityDesign.Folder)].Update(parent.Path);
                }

                if (Parent == null) throw new InvalidOperationException($"{nameof(Parent)} cannot be null");
                var operation = new EntityFolderOperation(Asset, EntityFolderOperation.Action.FolderRenamed, Path, oldName, Parent.Owner.Id);
                Editor.UndoRedoService.PushOperation(operation);
                Editor.UndoRedoService.SetName(transaction, $"Rename folder '{oldName}' to '{newName}'");
            }
        }
    }
}

View on GitHub (pinned to 96fad776d2)