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Migrate to System.Text.Json (JSON)

  • Artikkeli

The System.Text.Json library defaults to emphasizing literal, deterministic behavior and avoids any guessing or interpretation on the caller's behalf. The library is intentionally designed this way for security and performance. While System.Text.Json is highly configurable and its features can be used to minimize changes needed to serialized types, it's important to consider the trade-offs between handling existing types with as few changes as possible vs. refactoring types to enable idiomatic and secure serialization.

When migrating from BinaryFormatter to System.Text.Json, it's crucial to note the following behaviors and options:

  • By default, fields are not serialized or deserialized by System.Text.Json, but they can be annotated for serialization. Alternatively, JsonSerializerOptions.IncludeFields can be cautiously set to true to include all public fields for the types being serialized.

    JsonSerializerOptions options = new()
{
    IncludeFields = true
};

  • By default, System.Text.Json ignores private fields and properties. You can enable use of a non-public accessor on a property by using the [JsonInclude] attribute. Including private fields requires some non-trivial extra work.

  • System.Text.Json cannot deserialize read-only fields or properties, but the [JsonConstructor] attribute can be used to indicate that the specified constructor should be used to create instances of the type on deserialization. The constructor can set the read-only fields and properties.

  • To override the default serialization behavior for a specific type, you can write custom converters.

  • It supports serialization and deserialization of many collections, but there are limitations. See the supported types documentation for details on which types and collections are supported for serialization and deserialization.

  • Under certain conditions, it supports serialization and deserialization of custom generic collections.

  • Other types without built-in support are: DataSet, DataTable, DBNull, TimeZoneInfo, Type, ValueTuple. However, you can write a custom converter to support these types.

  • It supports polymorphic type hierarchy serialization and deserialization where the types have been explicitly opted in via the [JsonDerivedType] attribute or custom converter. Open inheritance hierarchies are not supported, and round-tripping with polymorphism requires type discriminator identifiers for all known derived types.

  • The [JsonIgnore] attribute on a property causes the property to be omitted from the JSON during serialization.

  • To preserve references and handle circular references in System.Text.Json, set JsonSerializerOptions.ReferenceHandler to ReferenceHandler.Preserve.

  • Serialization can be extensively customized with custom contracts, unblocking many scenarios while minimizing changes to serialized types.