How to improve performance when there are many TextBlocks in ItemsControl items?

Question

   Hi,
   I'm trying to find a way to improve performance for a situation when there is an ItemsControl using UI and Data virtualization and each item on that control has 36 TextBlocks. Basically the item is a single string. There are so many TextBlocks
to allow assigning different brushes to different parts of the string. Performance of this construction is terrible. I have 37 items visible on the screen and if I try to scroll up or down it scrolls into the black space and then it takes a second or two to
show the items.
   I tried different things. For example, the most successful performance-wise was to replace TextBlocks with Borders and then draw bitmaps. In other words, I prepared 127 bitmaps for each character (I need ASCII only) and then I used those bitmaps
to set Border.Backgrounds. It improved performance about 1.5 - 2 times but it consumed much more memory (which is not surprising, of course). Required amount of memory is so big that it throws OutOfMemoryException on 512MB emulator but works on 1GB. As a result
I don't thing it is a good solution.
   Another thing that worked perfect is to replace 36 TextBlocks with only 6 TextBlocks. In this case the performance improvement is about 5 - 10 times but I lose the ability to set different colors to different parts of the string. It seems that
the performance degrades dramatically with the increase of number of TextBlocks. Is there another technique to draw strings where literally each character can be of different color with decent performance?
Thank you
Alex

Answer 1

   Using Runs inside TextBlocks gives approximately the same improvement as using bitmaps 1.5 - 2 times faster but it is not even close to the case with just a couple of TextBlocks in the ItemsControl item. Any other ideas?
Alex