How Can I Deserialize Derived Types in JSON.NET While Preserving Type Information?

Json.net derived type deserialization

When processing JSON data, it can be advantageous to serialize and deserialize objects that follow a base-derived class relationship. However, Json.net (Newtonsoft) requires specific configuration to handle derived types efficiently.

Question:

Consider the following base and derived classes:

<code>public class Base
{
    public string Name;
}
public class Derived : Base
{
    public string Something;
}</code>

If you try to deserialize a JSON string containing base and derived class objects to List<Base>, you will only get the base class object, thus losing the derived type information.

Solution:

To successfully deserialize derived types, you need to enable type name handling. This can be achieved by creating a JsonSerializerSettings object and setting the TypeNameHandling property to All. Pass this settings object to serialization and deserialization operations:

<code>Base object1 = new Base() { Name = "Object1" };
Derived object2 = new Derived() { Something = "Some other thing" };
List<Base> inheritanceList = new List<Base>() { object1, object2 };

JsonSerializerSettings settings = new JsonSerializerSettings { TypeNameHandling = TypeNameHandling.All };
string Serialized = JsonConvert.SerializeObject(inheritanceList, settings);
List<Base> deserializedList = JsonConvert.DeserializeObject<List<Base>>(Serialized, settings);</code>

By enabling type name handling, Json.net will include type information in the JSON string. During deserialization, it will use this information to correctly recreate the derived object and populate deserializedList.

Note: Using this method exposes the names of all objects as well as the list itself in the serialized data. If this is a problem, consider alternative ways of handling polymorphic relationships.

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