using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Dynamic;

public class Program

{

    public class Item{

        public string Item1 {get; set;}

        public string Item2 {get; set;}

        public bool Condition {get; set;}

    }

    public static void Main()

    {

        var itemCollection = new List<Item> {

                new Item { Item1 = "Value 1-1", Item2 = "Value 1-2", Condition = true },

                new Item { Item1 = "Value 2-1", Item2 = "Value 2-2", Condition = false },

                new Item { Item1 = "Value 3-1", Item2 = "Value 3-2", Condition = true }

            };

​

        /*--------------------Using the old way-------------------------------------*/

        //Initialize a StringBuilder instance

        System.Text.StringBuilder str = new System.Text.StringBuilder();

        //Foreach item inside the data collection

        foreach (var item in itemCollection)

        {

            //if certain condition is met

            if (item.Condition == true)

            {

                //Then use data peices to format a string and append it to StringBuilder instance

                str.Append(String.Format("Item 1 = {0} : Item 2 = {1},", item.Item1, item.Item2));

            }

        }

        //There is going to be an extra comma at the end so remove it

        var outputOld = str.Remove(str.Length - 1, 1).ToString();

        /*-----------------------------------------------------------------------------*/

        /* --------------------------using Linq----------------------------------------*/

        var outputLinq = itemCollection

            .Where(item => item.Condition == true) //Filter collection that matches a condition

            .Select(s => String.Format("Item 1 = {0} : Item 2 = {1}", s.Item1, s.Item2)) //Projected into new sequence with modification to data

            .Aggregate( (a,b) => a + "," + b ) //Join the sequnce into one element

            .ToString(); //Optional conversion to string

        /*-----------------------------------------------------------------------------*/

        Console.WriteLine(outputOld);

        Console.WriteLine(outputLinq);

    }

}