Remove an item from an ObservableCollection in a CollectionChanged event handler

Question

I\'m hoping to be able to reject some items after they have been added to an ObservableCollection. I am not able to subclass the ObservableCollection or use any sort of view, s

Answer 1

I had tried using setting a flag to request collection add/remove changes and then when the System.Windows.Interop.ComponentDispatcher.ThreadIdle called my handler, doing my add or remove. That works. However, using a try-finally in the collection changed handler to unwire and then rewire that same collection changed event handler also bypassed the re-entrance issue:

private void MyDataGrid_CollectionChanged( object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e )
{
    try
    {
        dgRows.CollectionChanged -= MyDataGrid_CollectionChanged;
        
        switch( e.Action )
        {
            case NotifyCollectionChangedAction.Add:
                if( SomeTestIsTrue() )
                dgRows.Add( new vmRowObject() );
                break;
        }
    }
    finally
    {
        dgRows.CollectionChanged += MyDataGrid_CollectionChanged;
    }
}