dotnet/wpf · error · InvalidOperationException

throw new…

Error message

throw new InvalidOperationException(SR.Format(SR.MemberNotAllowedForView, "CancelNew"));

What it means

CollectionViewProxy.CancelNew() forwards to the proxied view's IEditableCollectionView.CancelNew. If the proxied view does not implement IEditableCollectionView (null `ecv` at CollectionViewProxy.cs:482), the proxy throws InvalidOperationException because there is no AddNew transaction machinery to cancel.

Solutions

1. Guard with CanCancelNew before calling CancelNew
2. Ensure the underlying collection's view implements IEditableCollectionView (e.g. use ItemCollection/ListCollectionView-backed sources)
3. Add IEditableCollectionView support to a custom ICollectionView implementation

Example fix

// before
proxy.CancelNew();
// after
if (proxy.CanCancelNew)
{
    proxy.CancelNew();
}

if (!proxy.CanCancelNew) return;
proxy.CancelNew();

bool SupportsCancelNew(CollectionViewProxy p) => p?.ProxiedView is IEditableCollectionView;

try { proxy.CancelNew(); }
catch (InvalidOperationException ex) when (ex.Message.Contains("CancelNew")) { /* nothing to cancel / unsupported view */ }

When it happens

Trigger: Calling CollectionViewProxy.CancelNew() when the wrapped view does not implement IEditableCollectionView, or when no AddNew is possible on that view type.

Common situations: Canceling a 'new item' row in a data-bound grid backed by a collection view without edit support; refactoring code that previously bound to ListCollectionView to a custom view; unit tests invoking CancelNew on stub views.

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

• throw new…
• throw new…
• throw new…
• throw new…
• throw new…

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/97a7446728b7f314. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/Data/CollectionViewProxy.cs:482

            {
                throw new InvalidOperationException(SR.Format(SR.MemberNotAllowedForView, "CommitNew"));
            }
        }

        /// <summary>
        /// Complete the transaction started by <seealso cref="IEditableCollectionView.AddNew"/>.  The new
        /// item is removed from the collection.
        /// </summary>
        void IEditableCollectionView.CancelNew()
        {
            IEditableCollectionView ecv = ProxiedView as IEditableCollectionView;
            if (ecv != null)
            {
                ecv.CancelNew();
            }
            else
            {
                throw new InvalidOperationException(SR.Format(SR.MemberNotAllowedForView, "CancelNew"));
            }
        }

        /// <summary>
        /// Returns true if an </seealso cref="IEditableCollectionView.AddNew"> transaction is in progress.
        /// </summary>
        bool IEditableCollectionView.IsAddingNew
        {
            get
            {
                IEditableCollectionView ecv = ProxiedView as IEditableCollectionView;
                if (ecv != null)
                {
                    return ecv.IsAddingNew;
                }
                else
                {
                    return false;

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