using System;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var collection = new List<string>

        {

            "first",

            "second",

            "third"

        };

        var filtered = collection.Where(x => x == "second");

        foreach(var item in filtered)

        {

            Console.WriteLine(item);

        }

    }

}

​

public static class MyNewLinqExtensions

{

    public static IEnumerable<T> Where<T>(this IEnumerable<T> collection, Predicate<T> myPredicate)

    {

        foreach(var item in collection)

        {

            if (myPredicate(item))

            {

                yield return item;

            }

        }

    }

}