Silverlight - how to render image from non-visible data bound user control?

Question

Hello!

I have such situation - I'd like to build timeline control. So I have UserControl and ItemsControl on it (every row represents some person). The ItemsControl contains another ItemsControl as ItemsControl.ItemTemplate - it shows e.g. events for the person arranged by event's date.

So it looks as some kind of grid with dates as a column headers and e.g. peoples as row headers. ........................|.2010.01.01.....2010.01.02.....2010.01.03
Adam Smith....|......[some event#1].....[some event#2]......

John Dow.......|...[some event#3].....[some event#4].........

I can have a lot of persons (ItemsControl #1 - 100-200 items) and a lot of events occured by some day (1-10-30 events per person in one day)

the problem is that when user scrolls ItemsControl #1/#2 it happened toooo sloooooowwww due to a lot of elements should be rendered in one time (as I have e.g. a bit of text boxes and other elements in description of particular event)

Question #1 - how can I improve it? May be somebody knows better way to build such user control? I have to mention that I'm using custom Virtual panel, based on some custom Virtual panel implementation found somewhere in internet...

Question #2 - I'd like to make image with help of WriteableBitmap and render data bound control to image and to show image instead of a lot of elements. Problem is that I'm trying to render invisible data bound control (created in code behind) and it has actualWidth/Height equals to zero (so nothing rendered) even if I'm using Dispatcher.BeginInvoke(() => {...} approach. How can I solve it?

Thank you very much for you help!

Answer 1

About question #1: Nested ItemsControl virtualization is tricky. The problem is that even if the outermost control supports virtualization, the inner controls are measured with infinite length and thus instantiate all of their children. Instead of hosting an ItemsControl inside another, merge all data to the same list, using styling to simulate the hierarchy. Alternatively, find a commercial datagrid control that supports nested virtualization.