Good tip! I designed the improvements to box selection for VS 2010, so it's great to see box selection tips & tricks being shared :-)
For the curious, there are two other ways to accomplish the task shown in this tip:
1.) [VS 2008 and VS 2010] Make a box selection (in this case a standard selection would also work) around the entire area shown in the screenshot. Press Ctrl+H to bring up Quick Replace; "Look in: Selection" should be preselected automatically. Replace "int" with "double" in your selection, and you're done.
2.) [New for VS 2010] Make the box selection shown around the three "int"s. Now type "double." The text will be inserted on all three lines simultaneously, eliminating the need to copy and paste at all :-)
@AboutDev: You're right that this doesn't work in VS 2008, but it does in VS 2010. We've revamped Box Selection for VS 2010 and added a good bit of new functionality.
For details and a demo video of what's new for box selection in VS 2010, check out this post on the Visual Studio blog: http://blogs.msdn.com/visualstudio/archive/2009/10/26/box-selection-and-multi-line-editing.aspx
Brittany Behrens
Program Manager, VS Platform - Editor