using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        // here is a source list, like what we get originally out of dapper

        var chartList = new List<Chart>()

        { 

            new Chart() { Name  = "A" , Settings = "1"}, 

            new Chart() { Name  = "B" , Settings = "2"}, 

        };

        // our method we can choose to include xml or not

        bool includeSettings = false;

        // then we return an IEnumerable which can query chartList

        // notice how we are not doing anything here just defining the filter (or promise)

        var filter = chartList.Select(chart =>

        {

            Console.WriteLine(

                string.IsNullOrWhiteSpace(chart.Settings) 

                ? chart.Name + ".Settings is null!!!" 

                : chart.Name + ".Settings is not null");

            if(!includeSettings)

            {

                // this is modifing the property 

                // and will picked up on the next time 

                // the list is enumerated

                chart.Settings = null;

            }

            return chart;

        }); 

        // Force interation through the collection

        Console.WriteLine("First pass");

        filter.Count();

        // Force another interation through the collection

        Console.WriteLine("\r\nSecond pass");

        filter.Count();

    }

    public class Chart

    {

       public string Name {get; set;}   

       public string Settings {get; set;}   

    }

}

​