You can do it with the following converter:
public class MyModelConverter : JsonConverter
{
[ThreadStatic]
static bool cannotWrite;
// Disables the converter in a thread-safe manner.
bool CannotWrite { get { return cannotWrite; } set { cannotWrite = value; } }
public override bool CanWrite { get { return !CannotWrite; } }
public override bool CanConvert(Type objectType)
{
return typeof(MyModel).IsAssignableFrom(objectType);
}
public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
{
var obj = JObject.Load(reader);
obj.SelectToken("details.size").MoveTo(obj);
obj.SelectToken("details.weight").MoveTo(obj);
using (reader = obj.CreateReader())
{
// Using "populate" avoids infinite recursion.
existingValue = (existingValue ?? new MyModel());
serializer.Populate(reader, existingValue);
}
return existingValue;
}
public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
// Disabling writing prevents infinite recursion.
using (new PushValue<bool>(true, () => CannotWrite, val => CannotWrite = val))
{
var obj = JObject.FromObject(value, serializer);
var details = new JObject();
obj.Add("details", details);
obj["size"].MoveTo(details);
obj["weight"].MoveTo(details);
obj.WriteTo(writer);
}
}
}
public static class JsonExtensions
{
public static void MoveTo(this JToken token, JObject newParent)
{
if (newParent == null)
throw new ArgumentNullException();
if (token != null)
{
if (token is JProperty)
{
token.Remove();
newParent.Add(token);
}
else if (token.Parent is JProperty)
{
token.Parent.Remove();
newParent.Add(token.Parent);
}
else
{
throw new InvalidOperationException();
}
}
}
}
public struct PushValue<T> : IDisposable
{
Action<T> setValue;
T oldValue;
public PushValue(T value, Func<T> getValue, Action<T> setValue)
{
if (getValue == null || setValue == null)
throw new ArgumentNullException();
this.setValue = setValue;
this.oldValue = getValue();
setValue(value);
}
#region IDisposable Members
// By using a disposable struct we avoid the overhead of allocating and freeing an instance of a finalizable class.
public void Dispose()
{
if (setValue != null)
setValue(oldValue);
}
#endregion
}
And then use it like this:
[JsonConverter(typeof(MyModelConverter))]
public class MyModel
{
[JsonProperty("name")]
public string Name { get; set; }
[JsonProperty("size")]
public string[] Size { get; set; }
[JsonProperty("weight")]
public string Weight { get; set; }
}
public class TestClass
{
public static void Test()
{
string json = @"{
""name"" : ""widget"",
""details"" : {
""size"" : [
""XL"",""M"",""S"",
],
""weight"" : ""heavy""
}
}";
var mod = JsonConvert.DeserializeObject<MyModel>(json);
Debug.WriteLine(JsonConvert.SerializeObject(mod, Formatting.Indented));
}
}
The ReadJson()
method is straightforward: deserialize to a JObject
, restructure the appropriate properties, then populate the MyModel
class. WriteJson
is a little more awkward; the converter needs to temporarily disable itself in a thread-safe manner to generate a “default” JObject
that can be then restructured.