WCF: Proxy open and close - whaaa?

I am maintaing a Windows Forms application using WCF and are using Net.TCP internally. The lifecycle of our connections is GET/USE/CLOSE.

We are having a problem wi开发者_开发问答th the application pool crashing with no trace. In looking at netstat, I can see when I come into the application as we have a login service. However, even though we are creating the proxy in a using statement, the connection in netstat does not go away until I physically close the application.

Is this right? Should I be doing something different on the client to force the connection to close?

So if the connection stays open, does it stay open for the duration of the openTimeout setting and then gets torn down?

Microsoft says that you always have to close the connection at the end (see the example at MSDN). I've found the following pattern in this article about WCF disposal handling:

WCFServiceClient c = new WCFServiceClient();

try
{
    c.HelloWorld();
}
catch
{
    // acknowledge the Faulted state and transition to Closed
    c.Abort();

    // handle or throw
    throw;
}
finally
{
    c.Close();
}

The article says you should avoid using since it does not properly close and dispose the WCF service client object, you should do it with a try ... catch ... finally block instead as shown above - this way you're dealing with exceptions (which will abort and then re-throw or handle the exception) and also you take care of finally closing the connection. This is also clearly stated in Microsoft's WCF troubleshooting hints.

Note: The c.Close() in the finally does not do any harm in case of an exception (faulted state), because we call c.Abort() before the exception is re-thrown so the c.Close() does actually nothing in this case. However, if no exception occurs, then c.Close() is actually executed normally and the connection closes as expected.

If your WCF service behaves in a strange way, there are many (other) things which could cause this - here you can find some debugging hints.

First, you should probably not being using your proxy within the context of a using statement even though is does implement IDisposable: http://stevesmithblog.com/blog/idisposable-and-wcf/

That being said, it all depends on how you are utilizing the proxy. Take a look at marc's response here: C#, WCF, When to reuse a client side proxy

Yes, that's the expected behavior: the Net.TCP binding has a protocol-level transport session with your server, something you cannot really control in WCF.

I don't know of any mechanism in WCF to physically tear down that transport-level session - you might be able to do that using low-level TCP calls, but I've never had the need to do anything like that.