使用 JSON.net 进行 JSON 解析

发布于 2024-10-17 15:21:32 字数 1806 浏览 1 评论 0原文

我正在访问 facebook api 并使用 json.net 库 (newtonsoft.json.net) 我声明一个 Jobject 来解析内容并查找特定元素并获取它们的值。前几个一切正常，但后来我得到了这个无法解释的空异常错误“（对象引用未设置到对象的实例）

现在我查看了声明，但不知道如何更改它。任何帮助表示赞赏：

Dim jobj as JObject = JObject.Parse(responseData)
message = jobj("message").tostring

错误发生在上面的最后一行。我检查消息是否为空，然后查找下一个所需的字段，如下

catch exception..
  dim jobj2 as JObject = JObject.parse(responseData)
  description = jobj2("description").tostring

JSON 响应数据：

{
   "id": "5281959998_126883980715630",
   "from": {
   "name": "The New York Times",
   "category": "Company",
   "id": "5281959998"
},
  "picture": "http://external.ak.fbcdn.net  /safe_image.php?d=e207958ca7563bff0cdccf9631dfe488&w=
90&h=90&url=http\u00253A\u00252F\u00252Fgraphics8.nytimes.com\u00252Fimages\u00252F2011\u00252F02\u00252F04\u00252Fbusiness\u00252FMadoff\u00252FMadoff-thumbStandard.jpg",
  "link": "http://nyti.ms/hirbn0",
   "name": "JPMorgan Said to Have Doubted Madoff Long Before His Scheme Was Revealed",
   "caption": "nyti.ms",
   "description": "Newly unsealed court documents show that bank
   executives were suspicious of Bernard Madoff\u2019s accounts 
   and steered clients   away from him but did not alert regulators.",
   "icon": "http://static.ak.fbcdn.net/rsrc.php/yD/r/aS8ecmYRys0.gif",
   "type": "link",
   "created_time": "2011-02-04T16:09:03+0000",
   "updated_time": "2011-02-06T20:09:51+0000",
  "likes": {
  "data": [
     {
        "name": "Siege Ind.",
        "category": "Product/service",
        "id": "152646224787462"
     },
     {
        "name": "Lindsey Souter",
        "id": "100000466998283"
     },

这是一个示例，其中“消息”没有出现在前几行中，但稍后出现。我所做的就是寻找消息和描述的位置，然后先去获取它，如果我收到错误或字段不返回任何内容，我会尝试通过正则表达式进行解析，即使这样也无法正常工作。

原文

I am accessing the facebook api and using the json.net library (newtonsoft.json.net)
I declare a Jobject to parse the content and look for the specific elements and get their values. Everything works fine for the first few but then I get this unexplained nullexception error " (Object reference not set to an instance of an object)

Now I took a look at the declaration but cannot see how to change it. Any help appreciated:

Dim jobj as JObject = JObject.Parse(responseData)
message = jobj("message").tostring

The error occurs at the last line above.I check to see if message is null and then look for the next desired field as follows

catch exception..
  dim jobj2 as JObject = JObject.parse(responseData)
  description = jobj2("description").tostring

JSON responsedata:

{
   "id": "5281959998_126883980715630",
   "from": {
   "name": "The New York Times",
   "category": "Company",
   "id": "5281959998"
},
  "picture": "http://external.ak.fbcdn.net  /safe_image.php?d=e207958ca7563bff0cdccf9631dfe488&w=
90&h=90&url=http\u00253A\u00252F\u00252Fgraphics8.nytimes.com\u00252Fimages\u00252F2011\u00252F02\u00252F04\u00252Fbusiness\u00252FMadoff\u00252FMadoff-thumbStandard.jpg",
  "link": "http://nyti.ms/hirbn0",
   "name": "JPMorgan Said to Have Doubted Madoff Long Before His Scheme Was Revealed",
   "caption": "nyti.ms",
   "description": "Newly unsealed court documents show that bank
   executives were suspicious of Bernard Madoff\u2019s accounts 
   and steered clients   away from him but did not alert regulators.",
   "icon": "http://static.ak.fbcdn.net/rsrc.php/yD/r/aS8ecmYRys0.gif",
   "type": "link",
   "created_time": "2011-02-04T16:09:03+0000",
   "updated_time": "2011-02-06T20:09:51+0000",
  "likes": {
  "data": [
     {
        "name": "Siege Ind.",
        "category": "Product/service",
        "id": "152646224787462"
     },
     {
        "name": "Lindsey Souter",
        "id": "100000466998283"
     },

This is one example where "message" does not appear in the first few lines but appears later. So what I do is look for position of message and description and which ever is first go and get that and if I get an error or the fields do not return anything, I try and parse by regex and even that is not working right.

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