Data Virtualization with Hybrid Deferred Scrolling

[Adam]

Dear Telerik,

I am evaluating your silverlight grid for use in a large-dataset, high performance environment.
I have a very specific behavior requirement.
Data will be retrieved via REST services, and I require it to be virtualized with deferred scrolling ONLY when virtualized data needs to be loaded.

The behavior would be this:
Upon initially loading, 60 rows are visible in the grid (but the data-set is millions), and 3*60 rows are loaded per request (so 120 rows are off-screen).
The user starts scrolling, and because there are 120 more rows already loaded, immediate scrolling occurs. When the user scrolls into the last page (the last 60 rows in memory), the grid knows it will need to load more, so it makes the REST request - if the data has not loaded before the grid hits the last loaded row, then the grid switches to deferred scrolling.
If the user is still dragging (in deferred mode), but the visible rows become realised (the REST response arrives), then scrolling is switched back to immediate (i.e, the rows appear on screen).

With this behavior, the user is able to make fine scroll movements without any HTTP requests, and loaded rows are immediately visible, but if the user suddenly drags all the way to the bottom of the grid, then the last loaded rows become visible, and deferred scrolling takes over, reducing the number of REST calls made, while still providing a smooth scrolling action.

Is this achievable?

Thank you

[Nedyalko Nikolov]

Hi Adam,

Straight onto your questions:

1. Data will be retrieved on demand - this is exactly how out VirtualQueryableCollectionView works. You can take a look at this online demo. Also following blog posts are good starting point about DataVirtualization:

Data Virtualization for your Silverlight and WPF Applications
Telerik Data Virtualization, WCF RIA Services and Visual Studio Async CTP

2. Changing from real time scroll to deferred scroll and vice versa - unfortunately RadGridView does not support such "mixed" scroll mode.

Let me know if this doesn't help.

Regards,
Nedyalko Nikolov
the Telerik team