Process completed with exit code 81.

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'int IList.Add(object? value)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'bool IList.Contains(object? value)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'int IList.IndexOf(object? value)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'void IList.Insert(int index, object? value)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'void IList.Remove(object? value)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'value' doesn't match implemented member 'void IList.this[int index].set' (possibly because of nullability attributes).

Dereference of a possibly null reference.

Nullability of reference types in type of parameter 'sender' of 'void FilteredCollectionView<T, TFilterArg>.DataSource_ItemChanged(object sender, PropertyChangedEventArgs e)' doesn't match the target delegate 'PropertyChangedEventHandler' (possibly because of nullability attributes).

Possible null reference return.