<p>Is there a way to know which file is being selected in windows explorer? I've been looking at the tutorial posted here <a href="https://stackoverflow.com/questions/140312/tutorial-for-windows-shell-extensions">Idiots guide to ...</a> but the actions described are:</p>

<p>hover</p>

<p>context </p>

<p>menu properties </p>

<p>drag</p>

<p>drag and drop</p>

<p>I wonder if is there a method that get invoked when a file is selected. For instance to create a thumbnail view of the file. </p>

<p>Thanks.</p>

I could be way off, but it might be a security thing... I've gotten that error before, and I solved it... but I was up for days trying to get a lot of different bugs worked out.
I have a sample article doing something basic, but I'm using net.tcp (with security set to "None") here:
Duplex WCF Services Hosted in IIS Using Net.Tcp
Also, where are you getting the error... is it on the ".Close()" line, or the ".GetTasks().ToString()" line?
Another thing you can check is to simply telnet to localhost on port 9999 to see if the service is listening for incomming connections altogether.