XElementAttributePropertyDescriptor.cs

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using System;
using System.Xml.Linq;
 
namespace MS.Internal.Xml.Linq.ComponentModel;
 
internal sealed class XElementAttributePropertyDescriptor : XPropertyDescriptor<XElement, object>
{
    private XDeferredSingleton<XAttribute> _value;
 
    private XAttribute _changeState;
 
    public XElementAttributePropertyDescriptor()
        : base("Attribute")
    {
    }
 
    public override object GetValue(object component)
    {
        return _value = new XDeferredSingleton<XAttribute>((XElement e, XName n) => e.Attribute(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 XAttribute xAttribute2 && _value.element == xAttribute2.Parent && _value.name == xAttribute2.Name)
            {
                OnValueChanged(_value.element, EventArgs.Empty);
            }
            break;
        case XObjectChange.Remove:
            if (sender is XAttribute xAttribute && _changeState == xAttribute)
            {
                _changeState = null;
                OnValueChanged(_value.element, EventArgs.Empty);
            }
            break;
        }
    }
 
    protected override void OnChanging(object sender, XObjectChangeEventArgs args)
    {
        if (_value != null)
        {
            XObjectChange objectChange = args.ObjectChange;
            if (objectChange == XObjectChange.Remove)
            {
                XAttribute xAttribute = sender as XAttribute;
                _changeState = ((xAttribute != null && _value.element == xAttribute.Parent && _value.name == xAttribute.Name) ? xAttribute : null);
            }
        }
    }
}