Json.NET 5.0 Release 7 – Immutable Collections

Immutable Collections

The biggest new feature in Json.NET 5.0.7 is support for serializing and deserializing the offical new .NET Immutable Collections types.

string json = @"[
// deserializing directly to an immutable collection, what sorcery is this?!
ImmutableList<string> champions = JsonConvert.DeserializeObject<ImmutableList<string>>(json);
// Volibear

There is nothing you need to do to make immutable collection and Json.NET work together. Upgrade to Json.NET 5.0 Release 7, add the immutable collections NuGet package to your project and you can start using immutable collections with Web API, SignalR or directly from Json.NET like the example above.

Round-trip Extension Data

Extension data is now written when an object is serialized. Reading and writing extension data makes it possible to automatically round-trip all JSON without adding every property to the .NET type you’re deserializing to. Only declare the properties you’re interested in and let extension data do the rest.

public class CustomerInvoice
  // we're only modifing the tax rate
  public decimal TaxRate { get; set; }
  // everything else gets stored here
  private IDictionary<string, JToken> _additionalData;
string json = @"{
  'HourlyRate': 150,
  'Hours': 40,
  'TaxRate': 0.125
var invoice = JsonConvert.DeserializeObject<CustomerInvoice>(json);
// increase tax to 15%
invoice.TaxRate = 0.15m;
string result = JsonConvert.SerializeObject(invoice);
// {
//   'TaxRate': 0.15,
//   'HourlyRate': 150,
//   'Hours': 40
// }

Using extension data to round-trip JSON like this also means you don’t need to worry about third-party sources adding additional JSON because it will automatically be preserved when serializing/deserializing. Nifty.

If you don’t want extension data serialized (or deserialized) then disable that functionality by setting WriteData and ReadData properties on ExtensionDataAttribute to false.

Bug fixes

A couple of bugs crept into Json.NET after the flurry of releases earlier in the year. I have consulted with other developers and the consensus was that bugs are bad so this release fixes all known bugs.


Here is a complete list of what has changed since Json.NET 5.0 Release 6.

  • New feature - Added support for Immutable Collections
  • New feature - Added WriteData and ReadData settings to DataExtensionAttribute
  • New feature - Added reference and type name handling support to extension data
  • New feature - Added default value and required support to constructor deserialization
  • Change - Extension data is now written when serializing
  • Fix - Added missing casts to JToken
  • Fix - Fixed parsing large floating point numbers
  • Fix - Fixed not parsing some ISO date timezones
  • Fix - Fixed schema validation of integer value when type was number
  • Fix - Fixed writing of IConvertible values when TypeCode returned was Object
  • Fix - Fixed serializing proxy objects with no default constructor


Json.NET CodePlex Project

Json.NET 5.0 Release 7 Download – Json.NET source code and assemblies