C# Newtonsoft deserialize JSON array

Question

I'm trying to deserialize an array using Newtonsoft so i can display files from a cloud based server in a listbox but i always end up getting this error no matter what i try:

Newtonsoft.Json.JsonReaderException: 'Unexpected character encountered while parsing value: [. Path '[0].priv', line 4, position 15.'

Thisis an example try to deserialize:

[
 {
  "code": 200,
  "priv": [
     {
        "file": "file.txt",
        "ext": "txt",
        "size": "104.86"
     },
     {
        "file": "file2.exe",
        "ext": "exe",
        "size": "173.74"
     },

  ],
  "pub": [
     {
        "file": "file.txt",
        "ext": "txt",
        "size": "104.86"
     },
     {
        "file": "file2.exe",
        "ext": "exe",
        "size": "173.74"
     }
  ]
 }
]

I tried using a C# Class like this:

    public class ListJson
{
    [JsonProperty("pub")]
    public List List { get; set; }
}

public class List
{
    [JsonProperty("file")]
    public string File { get; set; }

    [JsonProperty("ext")]
    public string Ext { get; set; }

    [JsonProperty("size")]
    public string Size { get; set; }
}
    [JsonProperty("priv")]
public List List { get; set; }
}

public class List
{
    [JsonProperty("file")]
    public string File { get; set; }

    [JsonProperty("ext")]
    public string Ext { get; set; }

    [JsonProperty("size")]
    public string Size { get; set; }
}

And deserialize with:

List<list> fetch = Newtonsoft.Json.JsonConvert.DeserializeObject<List<list>>(json);

Have you used this to validate your JSON hint it has a syntax error — t0mm13b
– t0mm13b, Commented May 16, 2017 at 21:09
Also, there is a C# class called List - please refrain from confusing the name of classes that already exist. — t0mm13b
– t0mm13b, Commented May 16, 2017 at 21:12
If you are using Visual Studio - you can copy the JSON into memory using (ctrl+c) . Click on edit --> Paste Special --> Paste Json as Classes. — user4573148
– user4573148, Commented May 16, 2017 at 21:31

Federico Dipuma · Accepted Answer · 2017-05-16 21:29:26Z

13

The correct C# class structure for your JSON is the following:

public class FileEntry
{
    public string file { get; set; }
    public string ext { get; set; }
    public string size { get; set; }
}

public class FileList
{
    public int code { get; set; }
    public List<FileEntry> priv { get; set; }
    public List<FileEntry> pub { get; set; }
}

Deserializing it in this way:

var fetch = JsonConvert.DeserializeObject<FileList[]>(json);
var fileList = fetch.First(); // here we have a single FileList object

As said in the other answer, creating a class called List doesn't automagically turn it into a collection of objects. You need to declare the types to be deserialized from an array a collection type (e.g. List<T>, T[], etc.).

Small tip: when in doubt, use json2csharp.com to generate strongly typed classes from a json string.

edited May 16, 2017 at 21:29

answered May 16, 2017 at 21:15

Federico Dipuma

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6 Comments

Zeq Over a year ago

Now i'm stuck on actually using the deserialized json :/ i really suck at this

Federico Dipuma Over a year ago

@Zeq stuck where? Here it is a small demo on .NET Fiddle.

Zeq Over a year ago

Okay thanks a lot i will try to figure it out from here also the json gets downloaded from a server so it changes depending on the files

Brian Rogers Over a year ago

@Zeq what part changes?

Zeq Over a year ago

The json i use this to download the file on start client.DownloadFile("https://www.zeroside.co/api/list/" + fetch[0].id + "/" + fetch[0].token, zerolist);

|

Marc Gravell · Accepted Answer · 2017-05-16 21:10:22Z

0

At the moment List has a single List instance called priv, which despite the name: doesn't make it a list. To deserialize a JSON array ("priv": [...]), it needs to an array or list-like type, for example List<T> for some T. Presumably a List<FileThing>, if we assume that FileThing is actually the second type called List (you have 2).

answered May 16, 2017 at 21:10

Marc Gravell

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2 Comments

Zeq Over a year ago

My class is called list

Marc Gravell Over a year ago

@Zeq they're not both called List (at least: not in the same namespace)... because that isn't legal C#... but that isn't the point. The problem isn't the name... it is that it needs to be an array or list-like type. You could rename your List type(s) to Banana, and everything I said would remain identical.

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