Reduce function for events

events_reduce.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using OrderId = System.String;
using Address = System.String;
using System.Reactive.Subjects;

class Program
{        
    static void Main(string[] args)
    {       
        // Two initial events     
        var events = new List<dynamic>
        {
            new OrderCheckedOut
            {
                OrderId = "Foo1",
                EstimatedTotal = 12.0m,
                OrderNumber = "Foo1",         
                History = new List<string>{"Order Foo1 checked out" }
            },
            new OrderPaid
            {
                OrderId = "Foo1",
                PaidTotal = 12.0m,
                History = new List<string>{"Order Foo1 paid with 12.0$" }
            }
        };
            
        // Reduce to result document
        var docs = Reduce(events);
        var foo1Doc = docs.First();
        Console.WriteLine(foo1Doc);

        // Next events + document from last reduce
        var nextEvents = new List<dynamic>
        {
            foo1Doc,
            new OrderDispatched
            {
                OrderId = "Foo1",
                History = new List<string>{"Order Foo1 dispatched" }
            }
        };

        var docs2 = Reduce(nextEvents);
        var foo1Doc2 = docs2.First();
        Console.WriteLine(foo1Doc2);

        // Result is reduce of all three events.     
    }

    public static IEnumerable<OrderDocument> Reduce(IEnumerable<dynamic> input)
    {
        return from e in input
                group e by e.OrderId into g
                select new OrderDocument
                {
                    OrderId = g.Key,
                    OrderNumber = Last(g, gg => gg.OrderNumber),
                    OrderDate = Last(g, gg => gg.OrderDate),
                    EstimatedTotal = Last(g, gg => gg.EstimatedTotal),
                    PaidTotal = Last(g, gg => gg.PaidTotal),
                    History = g.SelectMany<dynamic, string>(gg => gg.History).ToList()
                };
    }

    private static dynamic Last(IEnumerable<dynamic> input, Func<dynamic, dynamic> selector)
    {
        foreach (var item in input.Reverse())
        {
            try
            {
                return selector(item);
            }
            catch{}
        }
        return default(dynamic);
    }
}


// Events
    
public class OrderCheckedOut
{
    public OrderId OrderId { get; set; }
    public string OrderNumber { get; set; }
    public DateTime OrderDate { get; set; }
    public decimal EstimatedTotal { get; set; }
    public IList<string> History { get; set; }
}

public class OrderAddressChanged
{
    public OrderId OrderId { get; set; }
    public Address Address { get; set; }
    public IList<string> History { get; set; }
}

public class OrderPaid
{
    public OrderId OrderId { get; set; }
    public DateTime PaymentDate { get; set; }
    public decimal PaidTotal { get; set; }
    public IList<string> History { get; set; }
}

public class OrderDispatched
{
    public OrderId OrderId { get; set; }
    public string Comments { get; set; }
    public IList<string> History { get; set; }
}

// Domain

public class OrderDocument 
{
    public OrderId OrderId { get; set; }
    public string OrderNumber { get; set; }
    public DateTime OrderDate { get; set; }
    public decimal EstimatedTotal { get; set; }
    public Address Address { get; set; }
    public DateTime PaymentDate { get; set; }
    public decimal PaidTotal { get; set; }
    public bool IsDispatched { get; set;}
    public string DispatchComments { get; set; }

    public IList<string> History { get ; set; }

    public OrderDocument ()
    {
        History = new List<string>();
    }
}