According to JSON.NET documentation, default behavior is to use int value for Enums : http://james.newtonking.com/projects/json/help/SerializationGuide.html
You can change that by adding a JsonConverter attribute with StringEnumConverter on your enum…
/// <summary>
/// The geometry type.
/// </summary>
[DataContract]
[JsonConverter(typeof(StringEnumConverter))]
public enum GeometryType
Documentation: Serialize with JsonConverters