ASP.NET Web API returning C# class

Question

In Web API Controller action method returns C# class, like that:

public class ShipController : ApiController
{
    [HttpGet]
    public Cell GetShip()
    {
        return new Cell(new ScriptEngine());
    }
}

Where Cell is my class, inherited from ObjectInstance from Jurassic JS library. When I call this action, ASP.NET tries to serialize my object to XML or JSON, and I get System.InvalidOperationException: "The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8'." I also tried to add [DataContract] attributes to class, as I found here, like that:

[DataContract]
public class Cell : ObjectInstance
{
    [DataMember]
    public int cellId;

    public Cell(ScriptEngine  engine) : base(engine)
    {
    }
}

But I still get error. How to make action return only my fields of class serialized, and not get into parent classes?

Answer 1

You want to serialize the Cell class only, not its parent class, right? The solution is: create a custom JSON converter. Here is the code:

Cell.cs

[JsonConverter(typeof(CellJsonConverter))]
public class Cell : Parent
{
    public int CellId { get; set; }
    public string Name { get; set; }

    public Cell(int id) : base(id)
    {
        CellId = id;
        Name = "This is a name";
    }
}

CellJsonConverter.cs

public class CellJsonConverter : JsonConverter
{
    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var cell = (Cell) value;

        writer.WriteStartObject();

        writer.WritePropertyName("cellId");
        serializer.Serialize(writer, cell.CellId);

        writer.WritePropertyName("name");
        serializer.Serialize(writer, cell.Name);

        writer.WriteEndObject();
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }

    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(Cell);
    }
}

When you call your API, you will get: {"cellId":10,"name":"This is a name"}.

JsonConverter is from Newtonsoft.Json.

Feel free to ask if there's something unclear to you :)