SandboxForRx.cs

    private static void GetValueIObservable2()
    {
        var repo = new AccountRepository();
        var accounts = repo.GetAccountWithSubs("123123123");
        //create a cold observable from IEnumerable...
        var accountObservable = accounts.ToObservable();
            //you can filter an IObservable just like an IEnumerable...
                //.Where(a => a.AccountNumber.ToString().StartsWith("2"));

        //create an observer that has the appropriate delegates... In this case we are only using the OnNext
        var observer = Observer.Create<Account>(acc =>
        {
            Console.WriteLine(acc.AccountNumber);
        });
        
        //subscribe to the observable... Since this is a cold observable that wraps an IEnumerable, the act of calling subscribe will iterate through the IEnumerable and call OnNext delegate for each.
        var subscription = accountObservable.Subscribe(observer);

        // instead of explicitly creating an observer, you can use this extension method when subscribing to just pass in the delegates.
        //var subscription = accountObservable.Subscribe(
        //    acc => Console.WriteLine(acc.AccountNumber),
        //    ex => { },
        //    () => { });
    }

    public class AccountRepository
    {
        public IEnumerable<Account> GetAccountWithSubs(string accountNumber)
        {
            yield return GetAccountAsync(accountNumber).Result;

            for (int i = 1000; i < 1200; i++)
            {
                yield return GetAccountAsync(i.ToString()).Result;
            }
        }

        public async Task<Account> GetAccountAsync(string accountNumber)
        {
            await Task.Delay(30);
            return new Account() {AccountNumber = accountNumber};
        }
    }

    public class Account
    {
        public string AccountNumber { get; set; }
    }