using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        // simulate event stream

        List<AccountEvent> events = new List<AccountEvent>

        {

            new AccountCreated {

                Type = "AccountCreated",

                CustomerId = "1234",

                AccountId = "abcd"

            },

            new CustomerDeposit {

                CustomerId = "1234",

                AccountId = "abcd",

                Amount = 1000.00M

            },

            new CustomerWithdrawal {

                CustomerId = "1234",

                AccountId = "abcd",

                Amount = 250.00M

            }

        };

​

        // project a usable state

        var denormalizer = new CustomerAccountDenormalizer();

        var state = denormalizer.ReplayState(events);

​

        Console.WriteLine($@"

            CustomerID: {state.CustomerId}

            AccountID: {state.AccountId}

            Balance: {state.Balance:C}

        "); 

    }

}

​

public class CustomerAccountDenormalizer

{   

    public Account ReplayState(IEnumerable<AccountEvent> events)

    {

        var account = new Account();

        foreach(var e in events)

            Handle((dynamic) e, account);

        return account;

    }

    private void Handle(AccountCreated e, Account state)

    {

        state.CustomerId = e.CustomerId;

        state.AccountId = e.AccountId;

    }

    private void Handle(CustomerDeposit e, Account state)

    {

        state.Balance += e.Amount;

    }

    private void Handle(CustomerWithdrawal e, Account state)

    {

        state.Balance -= e.Amount;

    }

}

​

public class Account

{

    public string CustomerId { get; set; }

    public string AccountId { get; set; }

    public decimal Balance { get; set; }

}

​

public class AccountEvent

{

    public string Type { get; set; }    

}

​

public class AccountCreated : AccountEvent

{

    public string AccountId { get; set; }   

    public string CustomerId { get; set; }

}

​

public class CustomerDeposit : AccountEvent

{

    public string CustomerId { get; set; }

    public string AccountId { get; set; }

    public decimal Amount { get; set; }

}

​

public class CustomerWithdrawal : AccountEvent

{

    public string CustomerId { get; set; }

    public string AccountId { get; set; }

    public decimal Amount { get; set; }

}