beginner AJAX questions (AJAX.net)

[darrel]

I've been playing with prototype.js and scriptaculous to create some nice
drag-and-drop interaction on my applications GUI. That's working well.

Now I want to take the next step and start passing data back and forth
between my page and the server via AJAX.

In terms of .net, can someone give me the overall concept?

Normally, I'd have a function in my codebehind that grabs a dataset and then
binds that to a control on my aspx page.

Are there ajax libraries (1.1) that interact with that concept, basically
'rebinding' a control over AJAX? Or is the concept more that I should have
the server side code do the produce the HTML and then send that back?

More specifically, I'm reading a bit of the ajax.net pro documentation:

http://www.ajaxpro.info/Examples/DataSets/default.aspx

where it talks about transferring datasets via the AJAX. I'm just not clear
on how one would use that to, say, update a repeater control (since that it
server-side concept, not client side).

I'm not looking for specific code right now...just trying to wrap my head
around the larger concept of what the server does vs. the GUI when trying to
update data on screen via AJAX.

Also, tangental question...does anyone know what the license for ajax.net
pro is? I can't seem to find anything on the site. Is it open source?
Commercial? Shareware?

-Darrel

 

[Flinky Wisty Pomm]

Are there ajax libraries (1.1) that interact with that concept, basically
'rebinding' a control over AJAX? Or is the concept more that I should have
the server side code do the produce the HTML and then send that back?

That's generally what I do for larger controls, but...

More specifically, I'm reading a bit of the ajax.net pro documentation:

http://www.ajaxpro.info/Examples/DataSets/default.aspx

where it talks about transferring datasets via the AJAX. I'm just not clear
on how one would use that to, say, update a repeater control (since that it
server-side concept, not client side).

You get back a dataset object serialized in JSON - you can use that to
update your controls manually. I often do this for dropdowns etc.
Return a List<T> serialized as JSON and use that to refresh my control
with a for loop.

Alternatively, you can pass a server control to your Ajax method,
update it on the server, and plonk it back on the page, but I've not
played with this and don't know how it handles Repeaters specifically.

I'm not looking for specific code right now...just trying to wrap my head
around the larger concept of what the server does vs. the GUI when trying to
update data on screen via AJAX.

The server is limited to returning data. Normally that'll be
ready-to-eat HTML, some kind of Javascript object, or XML. The latter
is falling out of favour these days, 'cos there's not much point to it
unless you're talking to a webservice.

What you do with the data on your side is up to you. Most frameworks
hand-wave this a bit, and have various clever tricks to make Ajax fit
into the Asp.Net model. Ajax pro doesn't - it sits outside the usual
model and is faster and possibly more flexible for it, but you do have
to go through a mental re-adjustment if you want to use it heavily. I'm
currently using it quite a bit with the same libraries as you are, and
it's a joy to behold - even if my script.aculo.us effects don't always
work perfectly under IE.

Also, tangental question...does anyone know what the license for ajax.net
pro is? I can't seem to find anything on the site. Is it open source?
Commercial? Shareware?

-Darrel

I think (don't quote me on this) it's a freebie to use, it's marked as
beta so don't cry if it doesn't work. From what I can gather, Michael
Schwarz is intending to produce a commercial version. It's largely
closed source, but he does distribute the occasional code dump. If I
really need to see what's happening, there's always Reflector.

Your best bet is to hop over to the Ajax.Net user group @
http://groups.google.co.uk/group/ajaxpro/ where the beautiful and
talented Mr Schwarz will be happy to answer your questions.

 

[darrel]

Flinky:

Wow. Lots of info! Thanks.

So, it sounds like you use AJAX.net in the method I was thinking, where
you'd return a chunk of HTML and then plop that back into the page via
javascript (innerhtml or the like, I assume).

That was my first inclination, but wanted to make sure I wasn't off base
thinking like that.

I often do that now just with standard codebehind, just because I like
having that fine-level of control over my HTML, but I know it breaks the
whole ideal of 'separate of data and presentation'.

You also mentioned the 'passing the server control' method which sounds
pretty slick, but I assume requires a much more integrated solution (ala
atlas) to use?

Again, thanks for the info!

-Darrel

 

[MSDN]

Flinky,

What happens if you pass just the data and hydrating it into the HTML.
Is this faster or just as you said send to the client html then plonk it.

Also when you said you can pass JavaScript objects to the client. Is that
correct or did I misunderstood you.

if so how do you dish out JavaScript objects from the server side.

can you serve any other objects to client and hydrate tags then?

I am trying to use ATLAS and trying to understand the architecture at high
level first then dig into details.

Thanks...

SA

Are there ajax libraries (1.1) that interact with that concept, basically
'rebinding' a control over AJAX? Or is the concept more that I should
have
the server side code do the produce the HTML and then send that back?

That's generally what I do for larger controls, but...

More specifically, I'm reading a bit of the ajax.net pro documentation:

http://www.ajaxpro.info/Examples/DataSets/default.aspx

where it talks about transferring datasets via the AJAX. I'm just not
clear
on how one would use that to, say, update a repeater control (since that
it
server-side concept, not client side).

You get back a dataset object serialized in JSON - you can use that to
update your controls manually. I often do this for dropdowns etc.
Return a List<T> serialized as JSON and use that to refresh my control
with a for loop.

Alternatively, you can pass a server control to your Ajax method,
update it on the server, and plonk it back on the page, but I've not
played with this and don't know how it handles Repeaters specifically.

I'm not looking for specific code right now...just trying to wrap my head
around the larger concept of what the server does vs. the GUI when trying
to
update data on screen via AJAX.

The server is limited to returning data. Normally that'll be
ready-to-eat HTML, some kind of Javascript object, or XML. The latter
is falling out of favour these days, 'cos there's not much point to it
unless you're talking to a webservice.

What you do with the data on your side is up to you. Most frameworks
hand-wave this a bit, and have various clever tricks to make Ajax fit
into the Asp.Net model. Ajax pro doesn't - it sits outside the usual
model and is faster and possibly more flexible for it, but you do have
to go through a mental re-adjustment if you want to use it heavily. I'm
currently using it quite a bit with the same libraries as you are, and
it's a joy to behold - even if my script.aculo.us effects don't always
work perfectly under IE.

Also, tangental question...does anyone know what the license for ajax.net
pro is? I can't seem to find anything on the site. Is it open source?
Commercial? Shareware?

-Darrel

I think (don't quote me on this) it's a freebie to use, it's marked as
beta so don't cry if it doesn't work. From what I can gather, Michael
Schwarz is intending to produce a commercial version. It's largely
closed source, but he does distribute the occasional code dump. If I
really need to see what's happening, there's always Reflector.

Your best bet is to hop over to the Ajax.Net user group @
http://groups.google.co.uk/group/ajaxpro/ where the beautiful and
talented Mr Schwarz will be happy to answer your questions.

 

[Flinky Wisty Pomm]

Oooh! Two messages to reply to, sorry if this gets a bit intermingled.

I can't give any info on ATLAS because I haven't touched it.

My gut feeling is that hydrating controls from javascript objects will
be slower than just chucking some HTML in place, but it gives you more
control and has some merits of its own - I've got a dropdown list in a
page, for example, which I populate from an array of JSON serialized
objects.

When the selectedIndex changes, I can look up the associated object and
pass that object back to the server, complete with all its properties,
making any changes I need to make before it goes. Pretty nice. I
haven't tested the performance implications of either technique because
the difference is likely to be minimal except for large controls. For
big chunks, I think HTML will be faster. Consider it for tables, layout
units etc. but being able to databind to objects which are valid on the
server and client is a real breath of fresh air.

Ajax pro supports the passing of server controls, but as I said, I
haven't had a go yet. You can pass a control to the server, alter it,
and pass it back to the client - I imagine that it's returned as HTML.
Note that Ajax.Net does NOT play with ViewState. Most of the frameworks
do, but take a performance/flexibility hit for sitting inside the
ASP.Net model - this annoys me a bit, but I got over it. See: Mental
re-adjustment. If you go all-out on Ajax.Net your pages end up _much_
thinner on the server.

Yes, SA you can pass Javascript objects to the client - Ajax.Net uses a
serializer that takes an object like

public class Foo
{
public string Bar
{
get{}
set{}
}
}

and returns a properties list string like {Bar:"value of Bar"}, Arrays
are serialized in the same way so a List<Foo> would serialize as
[{Bar:"somevalue"}, {"Bar:"Some other value"}, {Bar: "My third
value"}].

A deserializer on the server allows you to pass objects from the client
to the server and persist them to DB/ make changes and return them.
It's all quite neat.

I keep meaning to build a new serializer built on generics which I
think will be faster than the old object/casting one used in the
framework as it stands, but... deadlines, you know?

As to how you do it,

public class MyPage{

[AjaxPro.AjaxMethod]
public Foo MyAjaxMethod(int someArg)
{
return new Foo(someArg.ToString());
}
}

and in your javascript (the nasty way for brevity)

var myReturnObject = MyPage.MyAjaxMethod(10);
var myFoo = myReturnObject.value;
doSomethingWithFoo(myFoo);

HTH,

-- flink

 

[Flinky Wisty Pomm]

Reading through that, it's a bit biased toward strings, you could
equally do

public class MyPage
{
[AjaxPro.AjaxMethod]
public Foo MyOtherAjaxMethod(int someArg, DateTime someDate, Foo
someFoo)
{
AlterFoo(ref someFoo, someArg, someDate);
SaveFooToDb(someFoo);
return someFoo;
}
}

DateTimes and other basic types have their own serializers which make
more or less sense depending on the version you're running.

</flink>