What does the SignalR.Reactive library wants to be?

It's a binding for the Reactive Extensions for SignalR

What is so cool about it?

If you know Rx in general than you will probably know that the basic idea of Rx is to turn the programming model up side down (from imperative to reactive).

That's no different with these bindings. Where as the standard SignalR way is to call from the server into the client by calling client side JavaScript functions from within a .NET hub, with these bindings that's no longer the case. Instead you have a serverside Observable and map it one by one onto a Observable that lives on the clientside (of course, RxJS is needed on the client)

Ok, show me the codez

#Sample 1 - Having a serverside source that constantly produces values

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();

    RegisterGlobalFilters(GlobalFilters.Filters);
    RegisterRoutes(RouteTable.Routes);

    //HOT STUFF
    //We have a serverside IObservable<string> that gets published on the client side

    Observable
        .Interval(TimeSpan.FromSeconds(1))
        .Select(_ => DateTime.Now.ToLongTimeString())
        .ToClientside().Observable<RxHub>("SomeValue");
}

We essentially say, take this Observable and map it to the Observable property "SomeValue" that lives on the client. So working with them is trivial:

var myHub = $.connection.rxHub;
myHub.observe('SomeValue').subscribe(function (x) {
    $('#counter').html(x);
});
$.connection.hub.start();

#Sample 2 - Starting long running serverside operations that constantly give feedback about the progress Here we have the Controller Method "DoALongRunningOperation" which gets invoked by the client with an unique ID. Assume the operation exposes an Observable for a detailed log. We publish that Observable with the ID as its name to the client:

public void DoALongRunningOperation(string id)
    {
        var subject = new Subject<string>();

        Task.Factory.StartNew(() =>
        {
            subject.OnNext("just started");
            Thread.Sleep(1000);
            subject.OnNext("One second passed, I'm still running");
            Thread.Sleep(5000);
            subject.OnNext("Another five seconds passed, I'm still running");
            Thread.Sleep(5000);
            subject.OnNext("Almost done");
            subject.OnCompleted();
        });

        subject.ToClientside().Observable<RxHub>(id);
    }
}

Clientside, we invoke the Controller method and subscribe to the dynamically created Observable

var guid = new Date().getTime().toString();

$('#button').click(function () {
    $('#button').attr('disabled', true);
    myHub.observe(guid)
        .subscribe(function (log) {
            $('#operationLog').append(log);
            $('#operationLog').append('<br>');
        }, function () {
            $('#operationLog').append('fatal error');
            $('#operationLog').append('<br>');
        }, function () {
            $('#operationLog').append('we are done!');
            $('#operationLog').append('<br>');
            $('#button').attr('disabled', false);
        });
    $.get('/Home/DoALongRunningOperation/' + guid);
});

Both examples can be found in this solution. Just grab the code and run it!

What's left to say

This version of SignalR.Reactive works with SignalR 0.5