I’ve been thinking about the number of projects we have inhouse that are still being developed using visual studio 6 and how best to migrate them forward onto visual studio 2008. The projects range in flavours of C/C++ and VB.
Is it better to let VS2k8 convert the workspaces into solutions, fix any compile errors and be on your merry way? Or, is it better to start with a clean solution and migrate code across project by project discarding dead code along the way?
The microsoft p&p team has recommended some strategies that answers this. Basically they recommend something like the project by project approach you mention. Of course, they're assuming a neatly architected application that has no nasty, dark corners from which late nights of coding and copious amounts of coffee spring from.
It doesn't hurt to let VS2K8 convert the project for you and see how much effort is required to fix the errors.
When I had to convert a VB6 app to VS2003 several years ago, I ran the converter and it produced something that basically compiled, but wasn't very good at all. I ended up having to modify a big chunk of the code it generated.
I would start with a clean solution, then run the converter on a project and copy over only the code you need. One of the big differences I noticed between a VB6 project and the converted VB.NET project (WinForm) was with the built-in controls. The converter would try to preserve the type of controls you were using, even if they were old and outdated. So you might be better served by creating new forms with modern controls (text boxes, tab controls, etc), then copy in the code that you need.