using System;
using System.Linq;
using System.Xml.Linq;

//XML: 
//<goods>
//  <good id="1">chair</good>
//  <good id="2">table</good>
//</goods>

var goods = new XElement("goods",
    new XElement("good", "chair", 
        new XAttribute("id", 1)),
    new XElement("good", "table", 
        new XAttribute("id", 2)));

//getting an element with the id = 1 attribute
//first method
var value1 = goods
    .Elements().Single(e => {
        var attr = e.Attribute("id");
        return attr != null && attr.Value == "1";
}).Value;
//value1 is "chair"

//second method
var value2 =
(from e in goods.Elements()
    let attr = e.Attribute("id")
    where attr != null && attr.Value == "1"
    select e)
    .Single().Value;
//value2 is "chair"

Console.WriteLine(value1);
Console.WriteLine(value2);