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4. Polymorphism

SharpYaml supports polymorphism in a JSON-like way by default: using a discriminator property within a mapping.

It also supports YAML tags as an alternative discriminator style.

JSON-like discriminator property

Use JsonPolymorphicAttribute and JsonDerivedTypeAttribute:

using System.Text.Json.Serialization;

[JsonPolymorphic(TypeDiscriminatorPropertyName = "$type")]
[JsonDerivedType(typeof(Dog), "dog")]
[JsonDerivedType(typeof(Cat), "cat")]
public abstract class Animal
{
    public string Name { get; set; } = "";
}

When serialized, a discriminator property is emitted:

$type: dog
Name: Rex

YAML tag discriminator

Use YamlPolymorphicAttribute and YamlDerivedTypeAttribute:

using SharpYaml.Serialization;

[YamlPolymorphic(DiscriminatorStyle = YamlTypeDiscriminatorStyle.Tag)]
[YamlDerivedType(typeof(Dog), "dog", Tag = "!dog")]
public abstract class TaggedAnimal
{
}

Notes

• For safety, runtime activation from tag type names is disabled by default.
• When using tags, prefer an explicit registry (YamlDerivedType/JsonDerivedType) over free-form type names.