SilverlightShow: Using Reactive Extensions in Silverlight Comments

RE: Using Reactive Extensions in Silverlight

RichardS — Sun, 31 Oct 2010 16:06:50 GMT

Great article. I learnt more from spending twenty minutes reading your article than from spending five hours watching the ching the Channel 9 Rx videos. Those Channel 9 guys could learn a lot about how to teach new concepts from YOU !!

RE: Using Reactive Extensions in Silverlight

Mads Lee Jensen — Fri, 21 May 2010 09:51:05 GMT

Thanks for this great post, watched some of the chn9 vidoes but didnt get the point of Rx this did a much better job. I wish i found this post before i saw the chn9 videos! then they probably would have made more sense!

RE: Using Reactive Extensions in Silverlight

Bell End — Thu, 01 Apr 2010 13:00:12 GMT

This comment has been removed, because of inappropriate content.

RE: Using Reactive Extensions in Silverlight

ppopadiyn — Thu, 25 Mar 2010 12:09:22 GMT

Hi Tim,

Another possible way, to do drag and drop is to use mouse offsets instead of mouse deltas. For example, the code that I am using in the article could be changed to this:

var mouseDown = from evnt in Observable.FromEvent( image, "MouseLeftButtonDown" )
                select evnt.EventArgs.GetPosition( image );
var mouseUp = Observable.FromEvent( image, "MouseLeftButtonUp" );
var mouseMove = from evnt in Observable.FromEvent( image, "MouseMove" )
                select evnt.EventArgs.GetPosition( this );

var query = from offset in mouseDown
            from position in mouseMove.TakeUntil( mouseUp )
            select new
            {
                X = position.X - offset.X,
                Y = position.Y - offset.Y
            };

query.Subscribe(
    point =>
    {
        Canvas.SetLeft( image, point.X );
        Canvas.SetTop( image, point.Y );
    } );

RE: Using Reactive Extensions in Silverlight

Tim Greenfield — Thu, 25 Mar 2010 00:44:09 GMT

Great article! For drag and drop operations you ought to call CaptureMouse and ReleaseMouseCapture right? I'm not sure what the best way to accomplish this is but one way that I got to work was:

from pos in mouseMove.SkipUntil(mouseLeftButtonDown.Do((o) => this.CaptureMouse())).

TakeUntil(mouseLeftButtonUp.Do((o) => this.ReleaseMouseCapture()))

RE: Using Reactive Extensions in Silverlight

Bobby Diaz — Thu, 11 Mar 2010 10:32:46 GMT

Great article! Thanks for sharing. By the way, after I read your article, I played around with a way to cut down on the amount of code needed to subscribe and combine multiple IObservables. Check out my blog post:

http://blog.bmdiaz.com/archive/2010/03/11/generate-strongly-typed-observable-events-for-the-reactive-extensions-for.aspx

Thanks!

RE: Using Reactive Extensions in Silverlight

ppopadiyn — Sun, 07 Mar 2010 21:52:12 GMT

@Keith, thanks for tip

@Florim, you won't have to wait too long, the next post is comming the next week ( RX + Web services ).

RE: Using Reactive Extensions in Silverlight

Florim Maxhuni — Sun, 07 Mar 2010 15:35:34 GMT

Very interesting post, and RX will be more interesting for me if will be more posts like this.

RE: Using Reactive Extensions in Silverlight

Keith Dahlby — Sat, 06 Mar 2010 17:54:07 GMT

One tip for "chatty" events like MouseMove is to use Throttle() to only capture one event per time interval (every 100ms, for example).

Cheers ~
Keith

RE: Using Reactive Extensions in Silverlight

Fallon Massey — Sat, 06 Mar 2010 10:16:06 GMT

I've looked at this stuff 6 ways to Sunday, but this is the FIRST article that made it make any sense to me.

GREAT Stuff!!!

RE: Using Reactive Extensions in Silverlight

Donald — Sat, 06 Mar 2010 03:30:25 GMT

A killer demo would be to have a duplex WCF service push notifications from the server to a silverlight background thread, then have the observable stuff update the UI.

RE: Using Reactive Extensions in Silverlight

Donald — Sat, 06 Mar 2010 03:02:47 GMT

I'm feel led astray by the words. I'm expecting that if I make something observable it will be observed... even if I add something later. If I subscribe it should do some work until I unsubscribe. Maybe some clarification in this area would help. It seems that the event stuff is the true observation/subscription work.

RE: Using Reactive Extensions in Silverlight

ppopadiyn — Fri, 05 Mar 2010 20:00:01 GMT

Hi Donald

Straight to first question. I beleive products.Add("Test") will no longer work, when the observable sequence ends (the Completed event is raised). What you need to do is to write something like this:

IObservable observable = Observable.Return( "Test" );
observable.Subscribe(
    p =>
    {
        lbObservable.Items.Add( p );
    } );

The second question (about the web services) is pretty interesting, and this is common issue for Silverlight. I'll try to prepare a small demo and will update the article.

@miantosca , thanks for the nice words.

RE: Using Reactive Extensions in Silverlight

miantosca — Fri, 05 Mar 2010 15:15:16 GMT

great article - watched the ch9 videos a while ago but this article did a better job of explaining how
you might use it so simplify otherwise very complex problems.

RE: Using Reactive Extensions in Silverlight

Donald — Fri, 05 Mar 2010 09:31:45 GMT

By the way, great article.. cleared up alot. I got notthing out of the ch9 videos.

RE: Using Reactive Extensions in Silverlight

Donald — Fri, 05 Mar 2010 09:07:44 GMT

I'm still confused on some aspects of this. I thought that I could click a button to products.Add("Test") and it would automatically be added to the list since it was being 'observed'. I even tried moving the products and observable to a high scope so they would go out of scope. I guess this is not what I want.
Would be nice to see how I could add to a list on a background thread data that comes from a web service and see the new data added to added to say a list control. I think it would be good for notifications.

I tried running the calculation with 10000 digits. During that the drag drop was too slow to work well.