Values passed to a wcf service in JSON Object are lost

Hi,
In the code below i am taking values from html controls and creating a json object. Values are retained till the service is called. In the service method all the data is lost or reset. Here is the code.
var data = {                     firstName: _firstName,                     lastName: _lastName,                     dob: _dob,                     id: _id,                     member: _member             &n ...