[politician]

Maybe that's true, but I'm working on a Windows Phone 7 app right now that struggling to hit its performance targets. The major culprit? Silverlight's data-binding. Microsoft shipped the framework without shipping high performance controls necessary to meet the certification requirements of their app store (ListBox, I'm looking at you), so while our code might return the results of the list in <20ms, it takes another 800-1500ms for the results to be rendered. It's frustrating.

[yread]

Have you tried using the virtualizing listbox?

[politician]

From my research, it looks like the Listbox enables UI virtualization by default. It didn't help. I ended up finding some helpful soul's NavigationListControl and limiting the number of results until the user taps a "show all" button. It helped a little. I think the final solution will be pre-allocating the first N data items with empty strings so that the initial cost of the Listbox is incurred at initial-page-layout-time rather than at keypress-time.

[yread]

I was solving similar problem but with a datagrid. I ended up adding my own scrollbar (so that I have better knowledge of what to preload) and populating the datagrid with an array of references to a single "Loading" object. The reduction in allocations sped it up a lot as well, I guess.