CODEWITHSUNDEEP
vb.netvisual-studio-2008json.net
vbNewbie
vbNewbie

Reputation: 3345

JSON parsing using JSON.net

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.

Upvotes: 0

Views: 3607

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1500505

Well, presumably jobj("message") has returned Nothing, which will happen if jobj doesn't have a message property. If you think this is incorrect, please post a short but complete piece of JSON to help us investigate.

(Is there any reason why you're declaring message and assigning it a value on the second line, only to overwrite that value on the third line?)

Upvotes: 2

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