stride3d/stride · error · InvalidOperationException

Multiple items in the collection are changing concurrently.

Error message

Multiple items in the collection are changing concurrently.

What it means

AutoUpdatingSortedObservableCollection subscribes to each item's PropertyChanging to preregister the changing item and its index for later reordering. If ItemPropertyChanging fires for a second item while ChangingItem still refers to a different item (no matching ItemPropertyChanged in between), the internal change-tracking invariant is broken and it throws.

Solutions

Ensure every PropertyChanging is paired with exactly one PropertyChanged on the same object, with no interleaved changes to other items
Fix item property setters that mutate other collection items while a change is in progress
Wrap multi-item mutations so each item's change completes before the next starts
Add a try/finally in setters so PropertyChanged fires even if intermediate code throws

Example fix

// before
public int Score
{
    get => score;
    set { score = value; neighbor.Score = value; } // cascades into another item mid-change
}
// after
public int Score
{
    get => score;
    set { SetProperty(ref score, value); } // cascade done from outside, sequentially
}

Defensive patterns

Strategy: validation

Validate before calling

// Audit item setters: ensure no setter mutates another item of the same collection while raising PropertyChanging/PropertyChanged

Try / catch

try { collection.UpdateItems(...); } catch (InvalidOperationException ex) { logger.Error(ex, "interleaved item change"); }

Prevention

Keep property setters self-contained — no cascading mutations of sibling items
Always pair PropertyChanging with PropertyChanged
Use try/finally so Changed fires even if setter code throws

When it happens

Trigger: Nested property changes on two different items within one PropertyChanging/PropertyChanged cycle, e.g. an item's property setter mutating another item already in the collection; exceptions in property setters that prevent PropertyChanged from firing.

Common situations: Interdependent view-models where one object's property change cascades into another's; batch updates that mutate several items inside one change scope; buggy INotifyPropertyChanged implementations that raise Changed without Changing.

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

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/08810cfbd72ca2d1. Report an issue: GitHub.

Appendix: source

Thrown at sources/presentation/Stride.Core.Presentation/Collections/AutoUpdatingSortedObservableCollection.cs:114

                propertyNames.Add(name);
            }
        }
    }

    /// <inheritdoc/>
    public override string ToString()
    {
        return $"{{AutoUpdatingSortedObservableCollection}} Count = {Count}";
    }

    protected virtual void ItemPropertyChanging(object? sender, PropertyChangingEventArgs e)
    {
        if (e.PropertyName is null || propertyNames?.Contains(e.PropertyName) == false)
            return;

        var item = (T?)sender;
        if (ChangingItem is not null && !ReferenceEquals(ChangingItem, item))
            throw new InvalidOperationException("Multiple items in the collection are changing concurrently.");

        ++changeCount;

        ChangingItem = item;
        ChangingIndex = GetIndex(item, false);
        AddedItem = null;
    }

    protected virtual void ItemPropertyChanged(object? sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName is null || propertyNames?.Contains(e.PropertyName) == false)
            return;

        var item = (T?)sender;

        // An object has been added while a property of an existing object has been modified
        if (ChangingItem is not null && AddedItem is not null)
            throw new InvalidOperationException("PropertyChanged is invoked without PropertyChanging, or multiple items in the collection are changing concurrently.");

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