Join operator return incomplete results

[smitpatel]

Repro code

public class Program
{
    public static void Main(string[] args)
    {
        var customers = new List<Customer>
            {
                new Customer {CustomerId = "ALFKI"},
                new Customer {CustomerId = "ANANT"},
                new Customer {CustomerId = "FISSA"}
            };
        var orders = new List<Order>
            {
                new Order { OrderId = 1, CustomerId = "ALFKI"},
                new Order { OrderId = 2, CustomerId = "ALFKI"},
                new Order { OrderId = 3, CustomerId = "ALFKI"},
                new Order { OrderId = 4, CustomerId = "FISSA"},
                new Order { OrderId = 5, CustomerId = "FISSA"},
                new Order { OrderId = 6, CustomerId = "FISSA"},
            };


        var syncResult = customers.Join(orders, c => c.CustomerId, o => o.CustomerId,
            (c, o) => new {c.CustomerId, o.OrderId});

        var asyncResult = customers.ToAsyncEnumerable().Join(orders.ToAsyncEnumerable(), c => c.CustomerId, o => o.CustomerId,
            (c, o) => new { c.CustomerId, o.OrderId });

        Console.WriteLine("Sync results");
        foreach (var pair in syncResult)
        {
            Console.WriteLine(pair.CustomerId + " " + pair.OrderId);
        }

        Console.WriteLine("");
        Console.WriteLine("Async results");
        using (var enumerator = asyncResult.GetEnumerator())
        {
            while (enumerator.MoveNext().Result)
            {
                Console.WriteLine(enumerator.Current.CustomerId + " " + enumerator.Current.OrderId);
            }
        }
    }
}

public class Customer
{
    public string CustomerId { get; set; }
}

public class Order
{
    public int OrderId { get; set; }
    public string CustomerId { get; set; }
}

Output:

Sync results
ALFKI 1
ALFKI 2
ALFKI 3
FISSA 4
FISSA 5
FISSA 6

Async results
ALFKI 1
ALFKI 2
ALFKI 3

Version info : System.Interactive.Async - 3.1.0-rc

Issue details:
Async join operator terminates if the key in outer does not match with any key in inner. Enumerable version skips of such key and return results from rest of keys.