using System;

using System.Linq;

using System.Xml.Linq;

​

public class Program

{

    public static void Main()

    {

        const string xml =

@"<Numbers>

    <Num>1</Num> 

    <Num>2</Num> 

    <Num>3</Num> 

    <Num>4</Num>

    <Num>5</Num> 

</Numbers>";

​

        var numList = XElement.Parse(xml)

            .Elements("Num")

            .Select(x => (int) x)

            .ToList();

​

        Console.WriteLine("Contains 3: {0}", numList.Contains(3));

        Console.WriteLine("Contains 6: {0}", numList.Contains(6));

    }

}

​