XDeferredAxis.cs

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using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;
 
namespace MS.Internal.Xml.Linq.ComponentModel;
 
internal sealed class XDeferredAxis<T> : IEnumerable<T>, IEnumerable where T : XObject
{
    private readonly Func<XElement, XName, IEnumerable<T>> _func;
 
    internal XElement element;
 
    internal XName name;
 
    public IEnumerable<T> this[string expandedName]
    {
        get
        {
            if (expandedName == null)
            {
                throw new ArgumentNullException("expandedName");
            }
            if (name == null)
            {
                name = expandedName;
            }
            else if (name != expandedName)
            {
                return Enumerable.Empty<T>();
            }
            return this;
        }
    }
 
    public XDeferredAxis(Func<XElement, XName, IEnumerable<T>> func, XElement element, XName name)
    {
        if (func == null)
        {
            throw new ArgumentNullException("func");
        }
        if (element == null)
        {
            throw new ArgumentNullException("element");
        }
        _func = func;
        this.element = element;
        this.name = name;
    }
 
    public IEnumerator<T> GetEnumerator()
    {
        return _func(element, name).GetEnumerator();
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}