Why WCF does not destroy the object when I close the client application without calling "Close" method on the client side?

Question

I have a net tcp WCF service as follows

    [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
    public class AVService : IAVService
    {
        static int _numberofInst = 0;
        public AVService()
        {
            ++_numberofInst;
            Console.WriteLine("Number of instances "+_numberofInst);
        }
        ~AVService()
        {
            --_numberofInst;
            Console.WriteLine("Number of instances " + _numberofInst);
        }
        public void Foo(){}
    }

When I create an object on the client side as follows

AVService client = new AVService();
client.Foo();

The constructor is called, but when I close the client application without calling close mehotd, the destructor does not been called? why? does this mean the service object still works on the server?

Answer 1

Yes - if you don't explicitly dispose of your client, the server will still "hang around" for a while (since you specified PerSession mode).

It will eventually time out (specified by the "InactivityTimeout" setting on the binding configuration), and will be destroyed - but that could take some time (several minutes to several hours, depending on your settings).

<bindings>
   <netTcpBinding>
      <binding name="NetTcp_Reliable" receiveTimeout="00:20:00">
         <reliableSession enabled="true" ordered="false" 
                          inactivityTimeout="00:15:00" />
      </binding>
   </netTcpBinding>
</bindings>

Therefore, it is the best practice to always dispose of your client before closing the app.

Marc