how does xmlnodelist.asqueryable() work?

i have a legit XmlNodeList lets call it nodelist

i can call nodelist.ChildNodes and that works

i can also call nodelist.ChildNodes.AsQueryable()

but then when i try nodelist.ChildNodes.AsQueryable().Where(x=>x....) that fails

i have included

using System.Linq

but im kinda at a loss how to

1. find specific nodes

2. count the nodes that start with a specific key ie

<key1 attrib1="xxx">yyy</key1>

how many nodes are there with key="key1"

thx for yr help