Hi Thys,
>> I need to do a GET to a Google service that requires an asynchronous client call.
I think you are misunderstanding their docs. There is no way a server can tell if the call is asynchronous or not, and they would never care about that. So I think whatever you are reading is referring to something completely different to what you think it's referring to.
>> The AsyncOpenUse property is 0 by default - meaning that it makes a synchronous call by default.
Alas, again, no. That's an incorrect interpretation of the property. That property is strictly to do with the connection being opened. Since connections are typically opened very very quickly, and it's easier to trap for errors on synchronous code, it defaults to opening synchronously. (Although you can change this if you like.)
>>When changed to 1 (implying AsyncOpenUse = true) anywhere (Init or before Open), the service keeps on rejecting the call saying it's not asynchronous.
I don't think it's rejecting you for the reasons you think. It might be helpful to post links to the service documentation explaining this requirement, or even posting the reply here that you receive from the service.
Cheers
Bruce