>> My Call Center Applicaton would communicate with heavy duty PBX systems, I thought the best result (the best application performance in heavy tasks conditions)
>
>Application performance in this case does not depend on the language. It depends on the design and the skills of the people involved. Depending on how you communicate with the PBX systems this might be better done in C++ or C#. But on any of the higher levels you don't gain anything with C# over VB.NET. I wouldn't worry about the language here, just pick what feels most comfortable. Rather spend the time on creating a design that allows for performance, ie. is asynchronous, queue driven, has clearly separate tiers, etc.

Actually, some of it can be done in VFP. I once wrote an interface to a Hitachi (IIRC, maybe Toshiba) system, using VFP7 and msComm.ocx - it was just receiving any news there were and writing them into tables (for hotel guests' phone billing), and occasionally sending some data in the other direction as well. I guess it still works, as I have had other contact with the system and this part never came up.