How do I deserialize a JSON object using NewtonSoft's JSON class?

Question

I'm working on a product in VB.NET and using the JSON class from NewtonSoft to process JSON. I don't know how to use it though and I can't seem to figure ou the doc. Basically, given a JSON string, I want to pull out the amount value. Here's what I have:

Dim serverResponse as String
Dim urlToFetch as String
Dim jsonObject as Newton.JSON.JSONConvert
Dim wc as new System.Net.WebClient
Dim amountHeld as String

urlToFetch = "someurl"
serverResponse = wc.DownloadString(urlToFetch)
jsonObject = Newtonsoft.Json.JsonConvert.DeserializeObject(serverResponse)

Now, at this point, I was hoping to be able to do a

amountHeld = jsonObject.Name["amount"]

to get the value of amount but I can't. I'm obviously doing it wrong. What is the proper way to do this?

Thanks! Anthony

What is the value of serverResponse? Just put a breakpoint at amountHeld line of code and inspect the value of jsonObject. — Styxxy
– Styxxy, Commented Jan 16, 2014 at 0:18
serverResponse holds the JSON string the server returns. I've validated that. The problem I have is that I know how to assign it to jsonObject but not how to retrieve a specific key. — CajunTechie
– CajunTechie, Commented Jan 16, 2014 at 0:20

Matt · Accepted Answer · 2014-01-16 02:03:04Z

You can use json.net to deserialize into a specific type, or an anonymous type, like this:

Dim serverResponse as String
Dim jsonObject as object
Dim amountHeld as String

serverResponse = "{amountheld: ""100""}"

Dim deserializedResponse = New With {.amountHeld = "1" }

jsonObject = Newtonsoft.Json.JsonConvert.DeserializeAnonymousType(serverResponse, deserializedResponse)

Console.WriteLine(jsonObject.amountHeld)

This creates an anonymous type with the property 'amountHeld' which json.net then uses to deserialize the json into.

An alternative approach would be to use Linq 2 JSON to parse the json and extract the values you want out of it similar to linq 2 xml:

Dim serverResponse as String
Dim jsonObject as object
Dim amountHeld as String

serverResponse = "{amountheld: ""100""}"

Dim o as JObject = JObject.Parse(serverResponse)

amountHeld = o.item("amountheld").ToString()

Console.WriteLine(amountHeld)

The JObject classes are in the Newtonsoft.Json.Linq namespace

Here is some more info on linq 2 json, unfortunately all the examples are in C#, but it might help you with what can and can't be done

sunil · Accepted Answer · 2014-01-16 00:24:04Z

0

Try it this way

var jsonObject = JsonObject.Parse(serverResponse);
var amount= jsonObject.GetNamedString("amount");

answered Jan 16, 2014 at 0:24

sunil

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1 Comment

CajunTechie Over a year ago

Ok so I see where you're going with it and that's actually the way I though it would be done. But I can't seem to actually FIND System.Json to use the class. Where is it?

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