c# parsing json: error reading json object

Question

I'm having some issues with fetching json values in c#.

https://i.sstatic.net/Uxn8e.png

Here is the code in question:

var json2 = new WebClient().DownloadString("http://fetch.json.url.here" + Input_Textbox.Text);
JObject o2 = JObject.Parse(json2);

string he_ident = (string)o2["he_ident"];
string le_ident = (string)o2["le_ident"];

Console.WriteLine(he_ident);
Console.WriteLine(le_ident);

Line 204 is: JObject o2 = JObject.Parse(json2);

The json is this: [{"le_ident":"06L","he_ident":"24R"},{"le_ident":"06R","he_ident":"24L"},{"le_ident":"07L","he_ident":"25R"},{"le_ident":"07R","he_ident":"25L"}]

I've also tried with just one set of le_ident and he_ident, such as [{"le_ident":"06L","he_ident":"24R"}] but it sill throws the same error.

Any ideas?

Since it looks like you're using JSON.Net, have you tried just using JsonConvert.Deserialize() in an alternative solution? — Richard Neil Ilagan
– Richard Neil Ilagan, Commented Jul 8, 2013 at 4:35

Richard Neil Ilagan · Accepted Answer · 2013-07-08 04:49:52Z

Personally, the cleanest approach to take is to define a class for the object signature you're expecting to take in:

class Entity {
    public he_ident { get;set; }
    public le_ident { get;set; }
}

Then just call DeserializeObject() into a collection:

var entities = JsonConvert.DeserializeObject<List<Entity>>(json2);

You should be able to access that then just like any C# object:

foreach(var entity in entities) {
    Console.WriteLine(entity.he_ident);
    Console.WriteLine(entity.le_ident);
}

This won't work if your JSON signature is dynamic though (or will be a bit tedious, as you'd have to define classes for each of your signatures).

But personally, I find that this approach does away with the muckiness that stuff like ArrayList had, and introduces strict typing into your code, which I find to generally lend itself to stronger, cleaner structure in a C# environment.

fcuesta · Accepted Answer · 2013-07-08 04:32:00Z

1

You should use JArray instead of JObject for json arrays:

    var json = new WebClient().DownloadString(...);
    JArray array = JArray.Parse(json);
    string he_ident = (string)array[0]["he_ident"]; 
    string le_ident = (string)array[0]["le_ident"];

answered Jul 8, 2013 at 4:32

fcuesta

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Comments

Natalie Adams · Accepted Answer · 2013-07-08 03:48:24Z

0

That JSON is a list not a dictionary.

So what you need to do is this:

string he_ident = (string)(((ArrayList)o2)[0])["he_ident"];

(Or simply loop through the list)

The JSON data:

{"le_ident":"06L"}

Should work with the code you have there.

answered Jul 8, 2013 at 3:48

Natalie Adams

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1 Comment

Spencer Over a year ago

I gave it a shot, but it throws this error: Cannot convert type 'Newtonsoft.Json.Linq.JObject' to 'System.Collections.ArrayList'

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