https://stackoverflow.com/questions/48724040/using-c-sharp-linq-to-search-an-xml-file

stack.48724040.cs

//<?xml version="1.0"?>
//<catalog>
//   <book id="bk101">
//      <author>Gambardella, Matthew</author>
//      <title>XML Developer's Guide</title>
//      <genre>Computer</genre>
//      <price>44.95</price>
//      <publish_date>2000-10-01</publish_date>
//      <description>An in-depth look at creating applications 
//      with XML.</description>
//   </book>
//   <book id="bk102">
//      <author>Ralls, Kim</author>
//      <title>Midnight Rain</title>
//      <genre>Fantasy</genre>
//      <price>5.95</price>
//      <publish_date>2000-12-16</publish_date>
//      <description>A former architect battles corporate zombies, 
//      an evil sorceress, and her own childhood to become queen 
//      of the world.</description>
//   </book>
//</catalog>

void Main()
{
	var xml = @"<?xml version='1.0'?>
<catalog>
   <book id='bk101'>
      <author>Gambardella, Matthew</author>
      <title>XML Developer's Guide</title>
      <genre>Computer</genre>
      <price>44.95</price>
      <publish_date>2000-10-01</publish_date>
      <description>An in-depth look at creating applications 
      with XML.</description>
   </book>
   <book id='bk102'>
      <author>Ralls, Kim</author>
      <title>Midnight Rain</title>
      <genre>Fantasy</genre>
      <price>5.95</price>
      <publish_date>2000-12-16</publish_date>
      <description>A former architect battles corporate zombies, 
      an evil sorceress, and her own childhood to become queen 
      of the world.</description>
   </book>
</catalog>";

	var term = "rain";

	var document = XDocument.Parse(xml);
	document.Dump("XDocument");

	var query = from element in document
					.Descendants("catalog")
					.Elements("book")
				let book = new
				{
					id = element.Attribute("id").Value,
					author = element.Element("author").Value,
					title = element.Element("title").Value,
					genre = element.Element("genre").Value
				}
				where book.author.ToLower().Contains(term)
					|| book.title.ToLower().Contains(term)
					|| book.genre.ToLower().Contains(term)
				select book;


	query.Dump();

}