using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

​

namespace HelloWorld

{

    public class Program

    {

        public static void Main()

        {

            string[] words = { "humpty", "dumpty", "set", "on", "a", "wall" };

            IEnumerable<string> query = from word in words 

                                        where word.Length == 3

                                        select word;

            foreach (string str in query)

                Console.WriteLine(str);

            IEnumerable<string> query2 = words.OfType<string>();

            foreach (string str in query2)

                Console.WriteLine(str);

        }

    }

}

​