Connection Pooling Problem

If within one application instance, stuff them all into an ArrayList, meaning that they are collected in one place. When you open then do an ArrayList.Add(object) and when you close then do an ArrayList.Remove(object), and when you want to know how many you've got do an ArrayList.Count.

Are you wanting to check across multiple instances of your application, or just within one. If you are checking against only one instance, what you could do is increment a global variable each time you use a connection, and decrement it when you close the connection. This would be the easiest way.