XElementElementPropertyDescriptor.cs

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using System;
using System.Xml.Linq;
 
namespace MS.Internal.Xml.Linq.ComponentModel;
 
internal sealed class XElementElementPropertyDescriptor : XPropertyDescriptor<XElement, object>
{
    private XDeferredSingleton<XElement> _value;
 
    private XElement _changeState;
 
    public XElementElementPropertyDescriptor()
        : base("Element")
    {
    }
 
    public override object GetValue(object component)
    {
        return _value = new XDeferredSingleton<XElement>((XElement e, XName n) => e.Element(n), component as XElement, null);
    }
 
    protected override void OnChanged(object sender, XObjectChangeEventArgs args)
    {
        if (_value == null)
        {
            return;
        }
        switch (args.ObjectChange)
        {
        case XObjectChange.Add:
            if (sender is XElement xElement2 && _value.element == xElement2.Parent && _value.name == xElement2.Name && _value.element.Element(_value.name) == xElement2)
            {
                OnValueChanged(_value.element, EventArgs.Empty);
            }
            break;
        case XObjectChange.Remove:
            if (sender is XElement xElement3 && _changeState == xElement3)
            {
                _changeState = null;
                OnValueChanged(_value.element, EventArgs.Empty);
            }
            break;
        case XObjectChange.Name:
            if (sender is XElement xElement)
            {
                if (_value.element == xElement.Parent && _value.name == xElement.Name && _value.element.Element(_value.name) == xElement)
                {
                    OnValueChanged(_value.element, EventArgs.Empty);
                }
                else if (_changeState == xElement)
                {
                    _changeState = null;
                    OnValueChanged(_value.element, EventArgs.Empty);
                }
            }
            break;
        }
    }
 
    protected override void OnChanging(object sender, XObjectChangeEventArgs args)
    {
        if (_value != null)
        {
            XObjectChange objectChange = args.ObjectChange;
            if ((uint)(objectChange - 1) <= 1u)
            {
                XElement xElement = sender as XElement;
                _changeState = ((xElement != null && _value.element == xElement.Parent && _value.name == xElement.Name && _value.element.Element(_value.name) == xElement) ? xElement : null);
            }
        }
    }
}