using System;

using System.Xml;

using System.Xml.Linq;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var xml = @"<dsPreventieRegisterItem xmlns='http://tempuri.org/dsPreventieRegisterItem.xsd'>

  <tblpreventieregisteritem>

    <id>1</id>

  </tblpreventieregisteritem>

  <tblpreventieregisteritem>

    <id>2</id>

  </tblpreventieregisteritem>

  <tblpreventieregisteritem>

    <id>3</id>

  </tblpreventieregisteritem>

               </dsPreventieRegisterItem> ";

        var root = XElement.Parse(xml);

        XNamespace d = "http://tempuri.org/dsPreventieRegisterItem.xsd";

        IEnumerable<XElement> items =

            from el in root.Elements(d + "tblpreventieregisteritem")

            orderby (int)el.Element(d + "id") descending

            select el;

        foreach (var item in items)

        {

            Console.WriteLine(item.Element(d + "id").ToString());

        }

    }

}