dotnet/wpf · error · InvalidOperationException

throw new…

Error message

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

What it means

CollectionViewProxy.RemoveAt(index) requires the proxied view to implement IEditableCollectionView, which owns removal-by-index. When the wrapped view lacks that interface (null `ecv` at CollectionViewProxy.cs:563), the proxy throws InvalidOperationException indicating RemoveAt is not allowed for this view.

Solutions

1. Check the view supports removal (cast ProxiedView as IEditableCollectionView != null) before RemoveAt
2. Remove the item from the underlying collection instead of the view, then let change notifications update the view
3. Switch the source collection to a mutable type whose view supports IEditableCollectionView

Example fix

// before
proxy.RemoveAt(0);
// after
var ecv = proxy.ProxiedView as IEditableCollectionView;
if (ecv != null)
{
    proxy.RemoveAt(0);
}

if (proxy.ProxiedView is IEditableCollectionView) { proxy.RemoveAt(index); }

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

try { proxy.RemoveAt(index); }
catch (InvalidOperationException ex) when (ex.Message.Contains("RemoveAt")) { /* fall back to removing from the source collection */ }

When it happens

Trigger: Calling RemoveAt on a CollectionViewProxy whose ProxiedView implements neither IEditableCollectionView nor an equivalent removal path (the `ecv` cast fails).

Common situations: Removing items from a read-only or fixed-size collection's view; views over arrays or immutable collections; data-binding controls that assume editable 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/0bbc65486303b7e6. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/Data/CollectionViewProxy.cs:563

                }
            }
        }

        /// <summary>
        /// Remove the item at the given index from the underlying collection.
        /// The index is interpreted with respect to the view (not with respect to
        /// the underlying collection).
        /// </summary>
        void IEditableCollectionView.RemoveAt(int index)
        {
            IEditableCollectionView ecv = ProxiedView as IEditableCollectionView;
            if (ecv != null)
            {
                ecv.RemoveAt(index);
            }
            else
            {
                throw new InvalidOperationException(SR.Format(SR.MemberNotAllowedForView, "RemoveAt"));
            }
        }

        /// <summary>
        /// Remove the given item from the underlying collection.
        /// </summary>
        void IEditableCollectionView.Remove(object item)
        {
            IEditableCollectionView ecv = ProxiedView as IEditableCollectionView;
            if (ecv != null)
            {
                ecv.Remove(item);
            }
            else
            {
                throw new InvalidOperationException(SR.Format(SR.MemberNotAllowedForView, "Remove"));
            }
        }

View on GitHub (pinned to 81131a70a4)