Discarding garbage characters after json object with Json.Net

Question

I have to consume a so called web service implemented by a dumb monkey which is returning some garbage after the proper Json response. Something like this:

{
  "Property1": 1,
  "Property2": 2,
  "Property3": 3
}<?xml version='1.0' ?>Maybe some other gibberish nonsense I wish to discard.

Now, I could just search for "<?xml" and split, but I was wondering if I can use a stream reader or something to read up to the closing } and then discard the rest.

I'm using C# and Json.Net.

http://stackoverflow.com/questions/524548/regular-expression-to-detect-semi-colon-terminated-c-for-while-loops/524624#524624 Look at the propsed solution, it's based on counting opening/closing brackets — Gusman, May 11 '16 at 20:05
I would like a robust solution. Given Json.Net has many advanced readers, I was wondering if using one of them instead of the standard JsonConvert I could get a JToken or something like that. — Alberto Chiesa, May 11 '16 at 20:06

score 2 · Accepted Answer · answered May 11 '16 at 21:50

2

You can also set JsonSerializerSettings.CheckAdditionalContent = false to tell the serializer to ignore any content after the end of the deserialized JSON object:

var result = JsonConvert.DeserializeObject<Dictionary<string, long>>(json, new JsonSerializerSettings { CheckAdditionalContent = false })

Oddly enough it is necessary to do this explicitly despite the fact that the default value seems to be false already, since the underlying field is nullable.

answered May 11 '16 at 21:50

dbc

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[Here specifically](https://github.com/JamesNK/Newtonsoft.Json/blob/6d7c94e69fa2f52b91fb22972321cb9b51b9abed/Src/Newtonsoft.Json/JsonConvert.cs#L856-L859) are the lines of code that are the culprit of requiring you to explicitly set the value to false. – Scott Chamberlain May 11 '16 at 22:02
@ScottChamberlain - yes, there's something a bit awkward going on here with how this setting interacts with [`JsonReader.SupportMultipleContent`](http://www.newtonsoft.com/json/help/html/P_Newtonsoft_Json_JsonReader_SupportMultipleContent.htm). I have a feeling `CheckAdditionalContent` was added later in such a way that `JsonConvert` would error by default when encountering additional content, but [fragment loops](http://www.newtonsoft.com/json/help/html/ReadMultipleContentWithJsonReader.htm) would not. – dbc May 11 '16 at 22:07

Alberto Chiesa · Answer 2 · 2016-05-11T20:27:29.407

I knew there had to be a simple and robust way:

    public T ReadTypeAndDiscardTheRest<T>(string json)
    {
        using (var sr = new StringReader(json))
        using (var jsonReader = new JsonTextReader(sr))
        {
            var token = JToken.Load(jsonReader);

            return token.ToObject<T>();
        }
    }

    [Test]
    public void TestJsonDiscarding()
    {
        var json = @"{""Key"":""a"", ""Value"":""n""}<?xml>aaaa";
        var kp = ReadTypeAndDiscardTheRest<KeyValuePair<string, string>>(json);

        Assert.That(kp.Key, Is.EqualTo("a"));
        Assert.That(kp.Value, Is.EqualTo("n"));
    }

As always, Json.Net FTW.

Discarding garbage characters after json object with Json.Net

2 Answers2

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