XmlElementListListener.cs

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namespace System.Xml;
 
internal sealed class XmlElementListListener
{
    private WeakReference<XmlElementList> _elemList;
 
    private readonly XmlDocument _doc;
 
    private readonly XmlNodeChangedEventHandler _nodeChangeHandler;
 
    internal XmlElementListListener(XmlDocument doc, XmlElementList elemList)
    {
        _doc = doc;
        _elemList = new WeakReference<XmlElementList>(elemList);
        _nodeChangeHandler = OnListChanged;
        doc.NodeInserted += _nodeChangeHandler;
        doc.NodeRemoved += _nodeChangeHandler;
    }
 
    private void OnListChanged(object sender, XmlNodeChangedEventArgs args)
    {
        lock (this)
        {
            if (_elemList != null)
            {
                if (_elemList.TryGetTarget(out var target))
                {
                    target.ConcurrencyCheck(args);
                    return;
                }
                _doc.NodeInserted -= _nodeChangeHandler;
                _doc.NodeRemoved -= _nodeChangeHandler;
                _elemList = null;
            }
        }
    }
 
    internal void Unregister()
    {
        lock (this)
        {
            if (_elemList != null)
            {
                _doc.NodeInserted -= _nodeChangeHandler;
                _doc.NodeRemoved -= _nodeChangeHandler;
                _elemList = null;
            }
        }
    }
}