Pesonally, I believe the PSVI is a really bad idea and would urge you to consider whether or not you really want to use PSVI in your application. It is a contentious issue. Some see it as a very good idea, others see it the other way.
A good place to start to see the issues is :
An example of PSVI usage (from VB on .NET) can be found here : http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconpostschemavalidationinfosetpsvi.asp