如何在VB.NET中检查JSON对象嵌套键是否存在

Question

{
  "data": {
    "stjCd": "",
    "lgnm": "AAA Enterprise",
    "stj": "",
    "dty": "Regular",
    "adadr": [],
    "cxdt": "",
    "gstin": "BBBBBBAAAAAA06",
    "nba": [
      "Recipient of Goods or Services",
      "Retail Business",
      "Wholesale Business",
      "Service Provision",
      "Works Contract"
    ],
    "lstupdt": "14/04/2018",
    "rgdt": "01/07/2017",
    "ctb": "Partnership",
    "pradr": {
      "addr": {
        "bnm": "ROAD",
        "loc": "ABC",
        "st": "OPP",
        "bno": "105, FOUR PLUS",
        "stcd": "Gujarat",
        "dst": "",
        "city": "",
        "flno": "",
        "lt": "",
        "pncd": "000000",
        "lg": ""
      },
      "ntr": "Recipient of Goods or Services, Retail Business, Wholesale Business, Service Provision, Works Contract"
    },
    "sts": "Active",
    "tradeNam": "ABC",
    "ctjCd": "",
    "ctj": "VI RANGE"
  }
}