WCF Closing Connection / Releasing Resources

I recently converted my ASMX service to WCF to take advantage of the sessions.

I looked through some of the training sessions on MSDN, but still not sure if I have a good setup in my code. this works for now, but I'm not quite sure why.

I got

[ServiceContract
    (SessionMode = SessionMode.Required,
     Namespace = "http://smartshopservice.org")]

Then i have

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
public class SmartShopService : SmartShopInterface
{
    private static Shopper sh = new Shopper();
    private List<aaa> data = new List<aaa>();

The first part of my question is whether Shopper are my "global" variables. I want him to always be there, while everything else, such as "data", was initiated per session. I also configured WebConfig accordingly. Anything else I need to do?

My second question is how to close the session and then reset all these variables? My client is now a web client, he communicates as follows:

static GarfieldService.SmartShopInterfaceClient service 
    = new GarfieldService.SmartShopInterfaceClient();

, , onbody = "" ASP.NET, , :

[WebMethod]
public static bool Connect() {
    try {
        if (service.State 
            == System.ServiceModel.CommunicationState.Closed) {
            service.Open();
            return true;
        }
        else if (service.State 
            == System.ServiceModel.CommunicationState.Created) {
            service.Open();
            return true;
        }
    }
    catch {}
    return false;
}

, , ?