Readonly property corrupts normal property object references.

[MagicShoebox]

Stack Overflow Thread

If the Deserializer encounters an object reference ("$ref": "2") that was originally defined in a readonly property (get; only), it fails to deserialize and returns null instead.

Class

public class Parent
{
    public Child ReadOnlyChild
    {
        get
        {
            return Child;
        }
    }

    public Child Child {get; set;}
}
public class Child
{
}

Serialization:

Parent p = new Parent() { Child = new Child() };
JsonConvert.SerializeObject(p, new JsonSerializerSettings()
{ Formatting = Formatting.Indented,
  PreserveReferencesHandling = PreserveReferencesHandling.Objects });

Serialized:

{
  "$id": "1",
  "ReadOnlyChild": {
    "$id": "2",
  },
  "Child": {
    "$ref": "2"
  }
}

Deserialized (& reserialized to show the change):

{
  "$id": "1",
  "ReadOnlyChild": null,
  "Child": null
}

Note that sometimes [JsonProperty(Order = #)] is needed to force the serializer to act on ReadOnlyChild first. Regardless, the above Serialized JSON block will fail to deserialize properly, even if the class has been modified to deserialize Child first.

To clarify, the problem is that the Child property is being read as null, not that ReadOnlyChild is unset.

[JamesNK]

Cool bug.

Fixed