[WebInvoke(RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.WrappedRequest)]
public IQueryable<Foo> GetFoos(int param1, DateTime param2, string param3)
{
  return CurrentDataSource.GetFoos(param1, param2, param3).AsQueryable();
}

config.SetServiceOperationAccessRule("GetFoos", ServiceOperationRights.AllRead);

[WebInvoke(Method = "POST")]
public IQueryable<string> GetFoos()
{
    List<string> foos = new List<string>();
    foos.Add("bar");
    return foos.AsQueryable();
}