using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var strList = new List<string>();

​

        strList.Add("first");

        strList.Add("second");

        strList.Add("third");

        strList.Add("fourth");

        var result = strList.Aggregate(

            Tuple.Create("", true),

            (val, current) => Tuple.Create(current, val.Item2 & Method(val.Item1, current)),

            val => val.Item2);

        Console.WriteLine(result);

    }

    private static bool Method(string prev, string cur)

    {

        // contrived result

        return cur != "third";

    }

}