using System;

using System.Linq;

using System.Collections.Generic;

public class Item

{

    public int Id { get; protected set; }

    public int Value { get; set; }

    public Item(int id, int val)

    {

        Id = id;

        Value = val;

    }

}

​

public class Rule

{

    protected readonly string _name;

    public IEnumerable<Item> Input { get; protected set; }

    public IEnumerable<Item> Output { get { return Apply(); } }

    public Rule (IEnumerable<Item> input, string name)

    {

        Input = input;

        _name = name;

    }

    protected virtual IEnumerable<Item> Apply()

    {

        foreach (var item in Input)

        {

            Console.WriteLine("Applying {0} {1} to Item.Id {2}", nameof(Rule), _name, item.Id);

            item.Value += 1;

            yield return item;

        }

    }

}

​

public class StatefulRule : Rule

{

    public StatefulRule(IEnumerable<Item> input, string name) : base(input, name) { }

    protected override IEnumerable<Item> Apply()

    {

        var fullSetOfModifiedData = new List<Item>();

        var sum = 0;

        foreach (var item in Input)

        {

            Console.WriteLine("Applying {0} {1} to Item.Id {2}", nameof(StatefulRule), _name, item.Id);

            sum += item.Value;

            item.Value = sum;

​

            yield return item;

        }

    }

}

​

public class BlockingRule : Rule

{

    public BlockingRule(IEnumerable<Item> input, string name) : base(input, name) { }

    // Reverses input so requires full data set

    protected override IEnumerable<Item> Apply()

    {

        var fullSetOfModifiedData = new Stack<Item>();

        foreach (var item in Input)

        {

            fullSetOfModifiedData.Push(item);

            Console.WriteLine("Applying {0} {1} to Item.Id {2}", nameof(BlockingRule), _name, item.Id);

        }

        Console.WriteLine("Finished applying {0} {1}, unblock next rule", nameof(BlockingRule), _name);

        return fullSetOfModifiedData;

    }

}

​

public class Program

{

    public static void Main()

    {

        var input = Enumerable.Range(1, 5)

            .Select(x => new Item(x, x));

        var ruleA = new Rule(input,  "A");

        var ruleB = new Rule(ruleA.Output, "B");

        var ruleC = new StatefulRule(ruleB.Output, "C");

        var ruleD = new BlockingRule(ruleC.Output, "D");

        var ruleE = new Rule(ruleD.Output, "E");

        var ruleF = new Rule(ruleE.Output, "F");

        var processedItems = ruleF.Output;

        foreach (var item in processedItems)

        {

            Console.WriteLine("out: " + item.Value);

        }

        // IN

        // 1, 2, 3, 4, 5

        // After rule runs

        // A | 2,   3,   4,  5,  6

        // B | 3,   4,   5,  6,  7

        // C | 3,   7,  12, 18, 25

        // D | 25,  18, 12,  7,  3 

        // E | 26,  19, 13,  8,  4

        // F | 27,  20, 14,  9,  5

        // OUT

        // 27, 20, 14, 9, 5

    }

}