Make schemaless json serializable by web api

Question

I have a JSON string that contains an object that is complex, nested, and will likely change schema in the future. I would like to hand it off to a web API to serialize in the content negotiation pipeline as needed.

Is there any straightforward way of doing this? I've read other answers on SO, but they only discuss either cases where you know the schema you want beforehand (eg deserialize with JsonConvert.DeserializeAnonymousType) or when you know the nesting depth that you want to deserialize to.

So for example let's say I have the following string:

    @"{
      name: "Dan"
      children: [
         {
            name: 'Fred',
         },
         {
            name: 'Fannie',
            age: 30,
            children: {
                own: [
                    {name: "Barney"},
                    {name: "Angela"}
                ],
                adopted: {
                    {name: "Sven"}
                }            
            }  
        }
    }"

I don't know what the schema of it is, and it can change at any time, I just want to be able to send it via web api with proper content negotiation.

I can do JObject.Parse(...) but web api can't handle JObjects properly. It would handle dictionaries properly, but I can't seem to figure out how to use JSON.Net to deserialize dictionaries of arbitrary nesting depth.

Answer 1

As their documentation describes, Json.NET can convert directly from JSON to XML. Here's the example from their documentation:

string json = @"{
  '?xml': {
    '@version': '1.0',
    '@standalone': 'no'
  },
  'root': {
    'person': [
      {
        '@id': '1',
        'name': 'Alan',
        'url': 'http://www.google.com'
      },
      {
        '@id': '2',
        'name': 'Louis',
        'url': 'http://www.yahoo.com'
      }
    ]
  }
}";

XmlDocument doc = (XmlDocument)JsonConvert.DeserializeXmlNode(json);
// <?xml version="1.0" standalone="no"?>
// <root>
//   <person id="1">
//   <name>Alan</name>
//   <url>http://www.google.com</url>
//   </person>
//   <person id="2">
//   <name>Louis</name>
//   <url>http://www.yahoo.com</url>
//   </person>
// </root>

So either pass the JSON along as a string (unmodified) or convert to XML based on the requested content type.

Answer 2

So after a lengthy investigation I've managed to boil the problem down to this:

• Web Api by default uses the (now basically abandoned) XmlSerializer when content type of xml is specified
• XmlSerializer cannot serialize JObjects
• There is no built-in way to convert JObjects of arbitrary nesting depth to dictionaries (although a custom recursive function to do this wouldn't be terribly hard).

So the way to attack the problem is to implement your own xml formatter that converts to dictionaries or uses something like XSerializer. This sounds simple, but in a related 30 minute-long spike I was unable to get my custom formatter to fire.

In the end I simply removed the xml formatter as it's not strictly necessary for my api and is more trouble than it's worth.

Answer 3

I achieved exactly this by casting my dynamic objects as List<Dictionary<string, object>>. Please clarify if this is what you need.

Okey, after you updated your question it is clear that you don't even need to serialize it to dictionary. Just use Json.NET (It's built in in WebApi and it's being used as default JSON serializer btw).

Also, please make sure in future that you pass valid json.

Working example (WebApi2)

JSON Payload

{
    "name": "Dan",
    "children": [
        {
            "name": "Fred"
        },
        {
            "name": "Fannie",
            "age": 30,
            "children": {
                "own": [
                    {
                        "name": "Barney"
                    },
                    {
                        "name": "Angela"
                    }
                ],
                "adopted": [
                    {
                        "name": "Sven"
                    }
                ]
            }
        }
    ]
}

Code

public class DefaultController : ApiController
{
    [Route, HttpGet]
    public IHttpActionResult Test()
    {
        var json = "{\"name\": \"Dan\",\"children\": [{\"name\": \"Fred\"},{\"name\": \"Fannie\",\"age\": 30,\"children\": {\"own\": [{\"name\": \"Barney\"},{\"name\": \"Angela\"}],\"adopted\": [{\"name\": \"Sven\"}]}}]}";

        var obj = JsonConvert.DeserializeObject(json);

        return Ok(obj);
    }
}

Response