This can be done in the Demo application supplied, just open the C# example
1. Select lines 13-17
2. Type Ctrl+H to bring up the search and replace overlay, make sure selection is in the search combobox
3. Type 'error' into the search box, and 'aaaaaaa' into the replace box
4. Select lines 20-22
5. Click the replace all icon in the search overlay. The original section has its text replaced.