I recommend you follow my last advice. It will clearly show you the right syntax, so you don't have to keep trying to guess it.
Sorry, I don't have currently time to do it for you, so you'll better off doing it by yourself.
Note that I have no idea what you mean by "the idea used in the link below method (JsonServiceGroup1EchoContractListTest)".
By the way, don't pay attention just to the input string, but also whether you're using the right HTTP operation etc.