SerializationCallbacks.md

Serialization callbacks

A callback can be used to manipulate an object before and after its serialization and deserialization by the JsonSerializer.

• OnSerializing
• OnSerialized
• OnDeserializing
• OnDeserialized

To tell the serializer which methods should be called during the object's serialization lifecycle, decorate a method with the appropriate attribute (OnSerializingAttribute, OnSerializedAttribute, OnDeserializingAttribute, OnDeserializedAttribute).

Example

Example object with serialization callback methods:

public class SerializationEventTestObject :
    IJsonOnSerializing,
    IJsonOnSerialized,
    IJsonOnDeserializing,
    IJsonOnDeserialized
{
    // 2222
    // This member is serialized and deserialized with no change.
    public int Member1 { get; set; } = 11;

    // The value of this field is set and reset during and
    // after serialization.
    public string Member2 { get; set; } = "Hello World!";

    // This field is not serialized. The OnDeserializedAttribute
    // is used to set the member value after serialization.
    [JsonIgnore]
    public string Member3 { get; set; } = "This is a nonserialized value";

    // This field is null, but populated after deserialization.
    public string Member4 { get; set; }

    public virtual void OnSerializing() =>
        Member2 = "This value went into the data file during serialization.";

    public virtual void OnSerialized() =>
        Member2 = "This value was reset after serialization.";

    public virtual void OnDeserializing() =>
        Member3 = "This value was set during deserialization";

    public virtual void OnDeserialized() =>
        Member4 = "This value was set after deserialization.";
}

^{snippet source | anchor}

The example object being serialized and deserialized by Json.NET:

var obj = new SerializationEventTestObject();

Console.WriteLine(obj.Member1);
// 11
Console.WriteLine(obj.Member2);
// Hello World!
Console.WriteLine(obj.Member3);
// This is a nonserialized value
Console.WriteLine(obj.Member4);
// null

var json = JsonConvert.SerializeObject(obj, Formatting.Indented);
// {
//   "Member1": 11,
//   "Member2": "This value went into the data file during serialization.",
//   "Member4": null
// }

Console.WriteLine(obj.Member1);
// 11
Console.WriteLine(obj.Member2);
// This value was reset after serialization.
Console.WriteLine(obj.Member3);
// This is a nonserialized value
Console.WriteLine(obj.Member4);
// null

obj = JsonConvert.DeserializeObject<SerializationEventTestObject>(json);

Console.WriteLine(obj.Member1);
// 11
Console.WriteLine(obj.Member2);
// This value went into the data file during serialization.
Console.WriteLine(obj.Member3);
// This value was set during deserialization
Console.WriteLine(obj.Member4);
// This value was set after deserialization.

^{snippet source | anchor}