Small example on how to filter XML per value:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;

namespace ConsoleApp15
{
    class Program
    {
        static void Main(string[] args)
        {
            string strXML = @"
                <doc>
	                <ext>Type:A</ext>
	                <ext>Type:B</ext>
                </doc>";

            XElement myXML = XElement.Parse(strXML);
            IEnumerable<XElement> xElementData = from data in myXML.Descendants("ext") where data.Value.Contains("Type:A") select data;
            foreach (XElement xElement in xElementData)
            {
                Console.WriteLine(xElement.Value);
            }

            Console.ReadKey();
        }
    }
}
POI:
IEnumerable xElementData = from data in myXML.Descendants("ext") where data.Value.Contains("Type:A") select data;