>For a VFP programer like me witch one between VB.net or C# should i learn

Don't limit yourself to two languages, you can always use Cobol.NET :) http://www.adtools.com/info/whitepaper/net.html

All kidding aside, it depends on a lot of factors. But as a VFP developer you should be able to pick any of the two (or three <g>) very easy.