Convert from Object to QueryString

How can I covert this object string

products=[{"PRICE":39.95,"RECIPIENT":{"ZIPCODE":"11779"},"CODE":"F1-509"}] 

to QueryString in C# as a parameter in an URL?

I still have a problem because products - a JSON encoded string containing an array of product structures .Products is the parameter of the URL which the RECIPIENT object is inside RootObject.

var order = new RootObject()

        {
            Price = 39.95,
            Code = "F1-509",
            Recipient = new RECIPIENT
            {
                Zipcode = "11779"
            }
        };

I need to convert Products Parameter to query which pass by URL in C# with GetAsync(URL).