Don't serialize properties with no setter

Question

I need to serialize objects (OpenTK.Vector2) containing properties with a getter but no setter. I would like these properties to be ignored in general, otherwise I end up with hugely inflated JSON from an object that has two relevant pieces of data (X and Y).

The code:

JsonSerializerSettings settings = new JsonSerializerSettings { ReferenceLoopHandling = ReferenceLoopHandling.Ignore };
Vector2 v = new Vector2 { X = 1, Y = 0 };
string json = JsonConvert.SerializeObject(v, settings);

produces the string:

{
   "X" : 1.0,
   "Y" : 0.0,
   "Length" : 1.0,
   "LengthFast" : 1.0016948,
   "LengthSquared" : 1.0,
   "PerpendicularRight" : {
      "X" : 0.0,
      "Y" : -1.0,
      "Length" : 1.0,
      "LengthFast" : 1.0016948,
      "LengthSquared" : 1.0,
      "PerpendicularRight" : {
         "X" : -1.0,
         "Y" : 0.0,
         "Length" : 1.0,
         "LengthFast" : 1.0016948,
         "LengthSquared" : 1.0,
         "PerpendicularRight" : {
            "X" : 0.0,
            "Y" : 1.0,
            "Length" : 1.0,
            "LengthFast" : 1.0016948,
            "LengthSquared" : 1.0
         }
      },
      "Yx" : {
         "X" : -1.0,
         "Y" : 0.0,
         "Length" : 1.0,
         "LengthFast" : 1.0016948,
         "LengthSquared" : 1.0,
         "PerpendicularRight" : {
            "X" : 0.0,
            "Y" : 1.0,
            "Length" : 1.0,
            "LengthFast" : 1.0016948,
            "LengthSquared" : 1.0
         } 
      }
   },
   "PerpendicularLeft" : {
      "X" : 0.0,
      "Y" : 1.0,
      "Length" : 1.0,
      "LengthFast" : 1.0016948,
      "LengthSquared" : 1.0,
      "PerpendicularLeft" : {
         "X" : -1.0,
         "Y" : 0.0,
         "Length" : 1.0,
         "LengthFast" : 1.0016948,
         "LengthSquared" : 1.0,
         "PerpendicularLeft" : {
            "X" : 0.0,
            "Y" : -1.0,
            "Length" : 1.0,
            "LengthFast" : 1.0016948,
            "LengthSquared" : 1.0
         },
         "Yx" : {
            "X" : 0.0,
            "Y" : -1.0,
            "Length" : 1.0,
            "LengthFast" : 1.0016948,
            "LengthSquared" : 1.0
         }
      }
   },
   "Yx" : {
      "X" : 0.0,
      "Y" : 1.0,
      "Length" : 1.0,
      "LengthFast" : 1.0016948,
      "LengthSquared" : 1.0,
      "PerpendicularLeft" : {
         "X" : -1.0,
         "Y" : 0.0,
         "Length" : 1.0,
         "LengthFast" : 1.0016948,
         "LengthSquared" : 1.0,
         "PerpendicularLeft" : {
            "X" : 0.0,
            "Y" : -1.0,
            "Length" : 1.0,
            "LengthFast" : 1.0016948,
            "LengthSquared" : 1.0
         },
         "Yx" : {
            "X" : 0.0,
            "Y" : -1.0,
            "Length" : 1.0,
            "LengthFast" : 1.0016948,
            "LengthSquared" : 1.0
         }
      }
   }
}

How can I get the serializer ignore these other properties?

Answer 1

Since you can't modify the OpenTK.Vector2 struct to add [JsonIgnore] property to the get-only properties, the easiest way to do this might be to write your own JsonConverter for it:

public class Vector2Converter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(OpenTK.Vector2);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        var temp = JObject.Load(reader);
        return new OpenTK.Vector2(((float?)temp["X"]).GetValueOrDefault(), ((float?)temp["Y"]).GetValueOrDefault());
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var vec = (OpenTK.Vector2)value;
        serializer.Serialize(writer, new { X = vec.X, Y = vec.Y});
    }
}

Then use it like:

        var settings = new JsonSerializerSettings();
        settings.Converters.Add(new Vector2Converter());
        Vector2 v = new Vector2 { X = 1, Y = 0 };
        string json = JsonConvert.SerializeObject(v, settings);
        Debug.WriteLine(json);

Which produces

{"X":1.0,"Y":0.0}

But if you really want to ignore all get-only properties everywhere on all classes and structs (which might have unforeseen consequences), see here: Is there a way to ignore get-only properties in Json.NET without using JsonIgnore attributes?.