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Json.NET

Serialization Callbacks

 

Json.NET supports serialization callback methods. 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:

Serialization Callback Attributes
Copy
public class SerializationEventTestObject
{
    // 2222
    // This member is serialized and deserialized with no change.
    public int Member1 { get; set; }

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

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

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

    public SerializationEventTestObject()
    {
        Member1 = 11;
        Member2 = "Hello World!";
        Member3 = "This is a nonserialized value";
        Member4 = null;
    }

    [OnSerializing]
    internal void OnSerializingMethod(StreamingContext context)
    {
        Member2 = "This value went into the data file during serialization.";
    }

    [OnSerialized]
    internal void OnSerializedMethod(StreamingContext context)
    {
        Member2 = "This value was reset after serialization.";
    }

    [OnDeserializing]
    internal void OnDeserializingMethod(StreamingContext context)
    {
        Member3 = "This value was set during deserialization";
    }

    [OnDeserialized]
    internal void OnDeserializedMethod(StreamingContext context)
    {
        Member4 = "This value was set after deserialization.";
    }
}

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

Serialization Callback Example
Copy
SerializationEventTestObject 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

string 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.
See Also