Errors parsing JSON using Newtonsoft.Json

Question

I am getting the following error when I try and parse my JSON using Newtonsoft.Json using

Response result = JsonConvert.DeserializeObject<Response>(unfilteredJSONData);

Can not add property string to Newtonsoft.Json.Linq.JObject. Property with the same name already exists on object.

I have no control over the JSON feed and they just added flags1 and flags2. The duplicate string seems to be causing the error, but I don't have any good idea on how to resolve it. This code was working well until the addition of the new fields.

Update:

The first error was caused by using an outdated version of JSON.net. There was a built-in version with the CMS system I am using and it was 3.5. When I use 4.5 I get a new error:

Can not add Newtonsoft.Json.Linq.JValue to Newtonsoft.Json.Linq.JObject.

It turns out my JSON below was not exactly the same format as what I am dealing with. Please note the update. The error seems to be caused here:

"flags1": {
    "string": "text",
    "string": "text"
},

The JSON is:

{
    "result":
    {
        "lookups":
        [
            {
                "groups":
                [
                    {
                        "item0": "text",
                        "item1": "text",
                        "item2": 0,
                        "item3": 0,
                        "item4": 11.5,
                        "item5": true
                    },
                    {
                        "item6": "text",
                        "oddName": "text"
                    },
                    {
                        "item7": {
                            "subitem0": "text",
                            "subitem1": 0,
                            "subitem2": true
                        },
                        "item8": {
                            "subitem0": "string",
                            "subitem1": 0,
                            "subitem2": true
                        }
                    },
                    {
                        "url": "http://google.com",
                        "otherurl": "http://yahoo.com",
                        "alturllist": [],
                        "altotherurl": []
                    },
                    {},
                    {
                        "flags1": {
                            "string": "text"
                        },
                        "flags2": {
                            "string": "text"
                        }
                    }
                ]
            },
            {
                "groups":
                [
                    {
                        "item0": "text",
                        "item1": "text",
                        "item2": 0,
                        "item3": 0,
                        "item4": 11.5,
                        "item5": true
                    },
                    {
                        "item6": "text",
                        "oddName": "text"
                    },
                    {
                        "item7": {
                            "subitem0": "text",
                            "subitem1": 0,
                            "subitem2": true
                        },
                        "item8": {
                            "subitem0": "string",
                            "subitem1": 0,
                            "subitem2": true
                        }
                    },
                    {
                        "url": "http://google.com",
                        "otherurl": "http://yahoo.com",
                        "alturllist": [],
                        "altotherurl": []
                    },
                    {},
                    {
                        "flags1": {
                            "string": "text",
                            "string": "text"
                        },
                        "flags2": {}
                    }
                ]
            }
        ]
    }
}

The C# classes are:

// response
[DataContract]
public class Response
{
    [DataMember(Name = "result")]
    public Result result { get; set; }
}
[DataContract]
public class Result
{
    [DataMember(Name = "lookups")]
    public List<Item> lookups { get; set; }
}
[DataContract]
public class Item
{
    [DataMember(Name = "groups")]
    public List<Dictionary<string, object>> groups { get; set; }
}

I have simplified the JSON and code example for clarity.

I included the code aspx to simplify reproducing.

test.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Test.aspx.cs" Inherits="Test" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <code>
    <%=response %>
    </code></div>
    </form>
</body>
</html>

test.aspx.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Runtime.Serialization;

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

using NLog;

public partial class Test : System.Web.UI.Page
{
    public string response = string.Empty;
    public static string cacheDirPath = HttpRuntime.AppDomainAppPath + "cache\\";
    private static Logger log = LogManager.GetLogger("productFeed");

    protected void Page_Load(object sender, EventArgs e)
    {

        response = readDataFromFile(cacheDirPath + "test2.json");
        Response masheryResult = JsonConvert.DeserializeObject<Response>(response);
    }
    private string readDataFromFile(string filePath)
    {
        string JSONData = string.Empty;
        try
        {
            StreamReader myFile = new StreamReader(filePath);

            JSONData = myFile.ReadToEnd();

            myFile.Close();
        }
        catch (Exception e)
        {
            log.Warn(e.Message);
        }

        return JSONData;
    }
}

// response
[DataContract]
public class Response
{
    [DataMember(Name = "result")]
    public Result result { get; set; }
}
[DataContract]
public class Result
{
    [DataMember(Name = "lookups")]
    public List<Item> lookups { get; set; }
}
[DataContract]
public class Item
{
    [DataMember(Name = "groups")]
    public List<Dictionary<string, object>> groups { get; set; }
}

No problems here with your example JSON. It deserializes just fine. — user530189
– user530189, Commented Jan 3, 2013 at 4:38
No issues for me as well. What version of Json.NET are you using, i'm using 4.5.0.0 from nuget. Is the above json the exact text you have deserialisation problem with, or just a representation. — Robert Slaney
– Robert Slaney, Commented Jan 3, 2013 at 6:55
@Robert Slaney - I was using the dll built into the Ektron's CMS system. Version 3.5, when I used the nuget version 4.5 the error goes away. Another error appears which I have to look into. 'Can not add Newtonsoft.Json.Linq.JValue to Newtonsoft.Json.Linq.JObject.' This isn't the exact code unfortunately what I am dealing with is much more unruly. Thank you. — whoacowboy
– whoacowboy, Commented Jan 3, 2013 at 19:40

Connie Hilarides · Accepted Answer · 2013-02-26 20:38:03Z

23

Both the properties in the "flags1" object are named "string", you can't define a property twice.

Edit: It seems that, at least in the latest nuget version, JObject.Parse skips over the error and properly parses the data! I hope you can make that work for you.

Here's an example of how you can do it:

Response result = JObject.Parse(unfilteredJSONData).ToObject<Response>();

edited Feb 26, 2013 at 20:38

answered Feb 26, 2013 at 15:13

Connie Hilarides

1,74515 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

whoacowboy Over a year ago

Thanks for the response, but I have no control over the JSON. Is there a work around by chance?

Jeff Schumacher Over a year ago

Does anyone know why this works and JsonConvert does not? What are the pros/cons of this approach?

Connie Hilarides Over a year ago

I think this approach works because JObject builds the tree dynamically, and JsonConvert tries to do it efficiently and complains with bad data. JsonConvert is definitely faster, and you should use it whenever it's possible, but in a case like this JObject is the best solution.

Trisped · Accepted Answer · 2020-08-10 23:38:43Z

3

In additional to Connor Hilarides answer, it can be used including arrays:

JToken resultToken = JToken.Parse(unfilteredJSONData);

edited Aug 10, 2020 at 23:38

Trisped

6,0442 gold badges51 silver badges65 bronze badges

answered Sep 8, 2015 at 16:39

quckly

692 bronze badges

Collectives™ on Stack Overflow

Errors parsing JSON using Newtonsoft.Json

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related