Are there any code samples out there which detect the presence of a web
service..ie windows app on a laptop which is able to talk to web services. If
the laptop is offline, detect that the service is unavailable and  prevent
actions which would call the web service.  

I have looked at the MS Smart Client App Block, but it seems like there's
screeds of code to basically check if there is any network connection..
ideally I'd like to check for a network connection, if there is one, check
for the web service..

I'm thinking that a dedicated thread, created at app start, which
periodically checks the net/web service availability asynchronously would be
the way to go?  To detect the presence of the web service, could I add a web
method which simply returns true (eg. serviceIsAvailable() ) , and put the
call to the service in a try catch?

Thanks

Russ