Unable to parse well formed JSON

Question

I issue a request to an API, and I'm able to parse the success response result (response.Content.ReadAsStringAsync().Result), but when I get a failure response ("bad request"), the seemingly well-formed JSON result cannot be parsed by JObject.Parse() or JToken.Parse(), they throw.

using System;
using Newtonsoft.Json.Linq;

public class Program
{
    public static void Main()
    {
        var result = "\"{\\\"error\\\":{\\\"detail\\\":\\\"java.lang.NullPointerException\\\",\\\"message\\\":\\\"Error occured while setting field 'caller_id' with value null\\\"},\\\"status\\\":\\\"failure\\\"}\"";

        var jObject = JObject.Parse(result);

        Console.WriteLine(jObject["error"]["message"]);
    }
}

The exception:

Run-time exception (line 10): Error reading JObject from JsonReader. Current JsonReader item is not an object: String. Path '', line 1, position 162.

Stack Trace:

[Newtonsoft.Json.JsonReaderException: Error reading JObject from JsonReader. Current JsonReader item is not an object: String. Path '', line 1, position 162.] at Newtonsoft.Json.Linq.JObject.Load(JsonReader reader, JsonLoadSettings settings) at Newtonsoft.Json.Linq.JObject.Parse(String json, JsonLoadSettings settings) at Newtonsoft.Json.Linq.JObject.Parse(String json) at Program.Main() :line 10

The exception points to the very end of the string, but I can't figure out what's missing. https://jsonblob.com can parse it after I remove the backslashes, I got rid of the apostrophe's, I "cleaned it up" with string and regex replace, I turned into a char array and build it again, all to no avail.

Help appreciated!

Why do you have so many slashes in your string? I ran your code with this string var result = "{\"error\":{\"detail\":\"java.lang.NullPointerException\",\"message\":\"Error occured while setting field 'caller_id' with value null\"},\"status\":\"failure\"}"; successfully. — yW0K5o
That's what comes back from the request, I'm guessing C# escapes a bit more. — hector-j-rivas

Luke Woodward Luke Woodward · Accepted Answer · 2019-05-01T21:18:42

The string you provide is well-formed JSON. It's what you get if you serialize some data to a JSON string and then serialize that string to a JSON string. To get the data out of the original JSON string, you therefore have to parse it twice.

The following works for me:

        var jToken = JToken.Parse(result);
        var jObject = JObject.Parse((string)((JValue)jToken).Value);

        Console.WriteLine(jObject["error"]["message"]);

Unable to parse well formed JSON

2 Answers