newtonsoft json deserialization error handling: partial deserialization

Question

Is there way to deserialize invalid json?

For example, next JSON deserialization will fail with JsonReaderException

{
 'sessionId': 's0j1',
 'commandId': 19,
 'options': invalidValue // invalid value
}

because options property value is invalid.

Is there a nice way to get sessionId and commandId values even if options value is invalid?

I know it's possible to handle errors during deserialization (http://www.newtonsoft.com/json/help/html/SerializationErrorHandling.htm)

var json = "{'sessionId': 's0j1', 'commandId': 19, 'options': invalidValue}"; 

var settings = new JsonSerializerSettings
{
    Error = delegate(object sender, ErrorEventArgs args)
    {
      args.ErrorContext.Handled = true;
    }
});
var result = JsonConvert.DeserializeObject(json, settings);

Bit it will result in result = null.

I don't think Json.NET can handle invalid Json. If you want to parse something that is not Json, have a look at this answer — Pikoh
– Pikoh, Commented Sep 8, 2016 at 6:48

Ivan Sveshnikov · Accepted Answer · 2019-01-28 14:05:28Z

4

You can do it with JsonReader.

Example code:

var result = new Dictionary<string, object>();

using (var reader = new JsonTextReader(new StringReader(yourJsonString)))
{
    var lastProp = string.Empty;
    try
    {
        while (reader.Read())
        {
            if (reader.TokenType == JsonToken.PropertyName)
            {
                lastProp = reader.Value.ToString();
            }

            if (reader.TokenType == JsonToken.Integer || 
                reader.TokenType == JsonToken.String)
            {
                result.Add(lastProp, reader.Value);
            }
        }
    }

    catch(JsonReaderException jre)
    {
        //do anything what you want with exception
    }
}

Note, that there is try..catch block as when JsonReader meets invalid character it throws JsonReaderException on reader.Read()

edited Jan 28, 2019 at 14:05

Ivan Sveshnikov

3954 silver badges11 bronze badges

answered Sep 8, 2016 at 6:57

Mikhail Tulubaev

4,28122 silver badges31 bronze badges

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