Recently I got an optimization problem in ASP.Net.
To be short, I had a Repeater with custom (somewhat complex) template on my Page, and I wanted to reload it asynchronously.

The first solution was XP and didin’t consider performance at all: wrap Repeater inside an UpdatePanel.
The problem was that the entire Page had to be repopulated on server just to get to the Repeater.

That gave me a choice of two headaches:

1. Put all Page/Controls data into ViewState and bloat bandwidth.
2. Query all additional data on the reload request and increase load on database to get data that will be thrown away.

To be honest, I could solve (2) with server-side cache, but, in my opinion, caching does not make ugly solutions any better, just faster.

So, naturally, my thought was to query the data-only WebService and then populate the Repeater on client.

And it was interesting to find out that Microsoft already has a client-side data binding solution within ASP.Net AJAX Futures.
I have found an excellent article on this matter by Xianzhong Zhu, “Unveil the Data Binding Architecture inside Microsoft ASP.NET Ajax 1.0″ (Part 1, Part 2).

I will now give a quick summary on the overall client-side binding architecture.
In essence it is quite similar to the smart DataSource controls of ASP.Net 2.0:
There is a DataSource javascript component and a ListView javascript control with html template.
ListView passes data from/to DataSource control, and DataSource talks with a JSON Web Service as a backend.
Controls and their relations are described in text/xml-script (Futures-only feature).

Everything seems quite straightforward and easy to use, I was quite happy to find it.
One thing that bothers me is the performance of text/xml-script (it is parsed on client).
But it is a concern not related to the current story.
The other question is what to do when I want to databind a complex list (consisting of several embedded server user controls) ?
I am going to find it out real soon.

Along the way, I have also noticed Sys.Preview.Data also introduces DataSets/DataTables to javascript.
That is quite funny. Personally, I never really considered DataSets acceptable anywhere above Persistence layer.
But I already thought about Persistence/DataAccess concept in javascript when I saw Gears.
And DataSets seem to fit ‘nicely’ to some GoogleGearsDataSource (it would be quite an experience to actually see one in real code).

Well, javascript O/R Mapper, anyone ?