Handling reference loops in JSON.net

Question

I wish to serialize a collection (List<Item>) of items to JSON.

These items have a collection of Connection which gives information about the connection from one Item to a second Item. And since the connection object has a reference to the items it makes it an infinite loop.

My question is is there a way for me to skip serialization of the connection collection when serializing the object the second time.

I've tried things like inheriting from JsonConverter and writing a custom WriteJson() method but from there I have no sence whether I should write out the array or not.

I've also tried using a custom ContractResolver but with no good results.

Classes

public class Item
{
    private static int _lastID = 0;

    public Item()
    {
        ID = ++_lastID;
        Connections = new List<Connection>();
    }


    public int ID { get; set; }

    public string Name { get; set; }

    public string Prop1 { get; set; }

    public string Prop2 { get; set; }

    public List<Connection> Connections { get; set; }

}



public class Connection
{
    private Connection(ConnectionType type, Item source, Item target)
    {
        if (type == ConnectionType.None)
            throw new ArgumentException();
        if (source == null)
            throw new ArgumentNullException("source");
        if (target == null)
            throw new ArgumentNullException("target");

        Type = type;
        Source = source;
        Target = target;
    }


    public ConnectionType Type { get; set; }

    public Item Source { get; set; }

    public Item Target { get; set; }


    public static void Connect(ConnectionType type, Item source, Item target)
    {
        var conn = new Connection(type, source, target);
        source.Connections.Add(conn);
        target.Connections.Add(conn);
    }
}

Wanted result:

[
    {
        "id": 1,
        "name": "Item #1",
        "prop1": "val1",
        "prop2": "val2",
        "connections": {
            "type": "ConnType",
            "source": {
                "id": 1,
                "name": "Item #1",
                "prop1": "val1",
                "prop2": "val2"
                // no connections array
            },
            "target": {
                "id": 2,
                "name": "Item #2",
                "prop1": "val1",
                "prop2": "val2"
                // no connections array
            }
        }
    },
    {
        "id": 2,
        "name": "Item #2",
        "prop1": "val1",
        "prop2": "val2",
        "connections": {
            "type": "ConnType",
            "source": {
                "id": 1,
                "name": "Item #1",
                "prop1": "val1",
                "prop2": "val2"
                // no connections array
            },
            "target": {
                "id": 2,
                "name": "Item #2",
                "prop1": "val1",
                "prop2": "val2"
                // no connections array
            }
        }
    }
]

EDIT:

C#

var settings = new JsonSerializerSettings
    {
        ContractResolver = new CamelCasePropertyNamesContractResolver(),
        ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
        Formatting = Formatting.Indented
    };
settings.Converters.Add(new StringEnumConverter());
var json = JsonConvert.SerializeObject(collection, settings);

Answer 1

Add this to your Global.asax (or in the WebApiConfig or any other config class)

var jsonFormatter = config.Formatters.OfType<JsonMediaTypeFormatter>().First();
jsonFormatter.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;

Answer 2

If I'm not mistaken you need to keep only the first depth of reference containing the connection collection? If that is the case, try using:

settings.ReferenceLoopHandling = ReferenceLoopHandling.Serialize;
settings.MaxDepth = 1;