Json.NET 5.0 Release 6 – Glimpse Plugin

The big new feature in this release is a Json.NET plugin for Glimpse. For anyone not familiar with Glimpse it is an open source diagnostics tool for ASP.NET, bringing the server-side information of a webpage into the browser. It is very useful and takes just a couple of minutes to get running.

The Glimpse Json.NET plugin adds a JSON tab to the Glimpse UI with information about each time Json.NET is used on the server, including:

  • Serialized type
  • Time taken
  • Any errors (with stack trace)
  • The complete JSON document

Being able to see the complete JSON document that Json.NET serialized or deserialized will be particularly useful when debugging unexpected results.

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The plugin also adds Json.NET events to the Glimpse timeline tab. The timeline tab is lets you see when and where Json.NET is used in a request. In the example below JSON is deserialized in the ASP.NET MVC controller action and then re-serialized in the Razor view.

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Today all calls to SerializeObject/DeserializeObject will automatically show up in Glimpse and going forward the frameworks that use Json.NET should also start appearing. Making all JSON actions on the server (deserializing the JSON request, serializing the JSON response, calls to JSON services like Web API/Facebook/Twitter, etc) visible in the browser for debugging without digging into tools like Fiddler will be very useful.

Download the Json.NET Glimpse plugin off NuGet now:

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Here is a complete list of what has changed since Json.NET 5.0 Release 5.

  • New feature - Added serialized/deserialized JSON to verbose tracing
  • New feature - Added support for using type name handling with ISerializable content
  • Fix - Fixed not using default serializer settings with primitive values and JToken.ToObject
  • Fix - Fixed error writing BigIntegers with JsonWriter.WriteToken
  • Fix - Fixed serializing and deserializing flag enums with EnumMember attribute
  • Fix - Fixed error deserializing interfaces with a valid type converter
  • Fix - Fixed error deserializing ISerializable objects that also implement IConvertible
  • Fix - Fixed potential infinite loop when parsing unquoted JSON values


Json.NET CodePlex Project

Json.NET 5.0 Release 6 Download – Json.NET source code and assemblies

Json.NET 5.0 Release 5 – DefaultSettings and Extension Data


If you have used Json.NET then you will be familiar with JsonSerializerSettings. This class has been an extremely successful at providing an simple way for developers to customize Json.NET.

With Json.NET’s increasing popularity and its use by more third party frameworks, a problem I have noticed is a developer has to customize serializer settings in multiple places. If you want your HtmlHelper.ToJson extension method, Web API services and SignalR to serialize JSON the same way across an application then you have to manually share a JsonSerializerSettings instance between them and figure out how each different framework allows you to customize Json.NET.

The solution I have come up with is to add global default settings. Set once with JsonConvert.DefaultSettings in an application, the default settings will automatically be used by all calls to JsonConvert.SerializeObject/DeserializeObject, and JToken.ToObject/FromObject. Any user supplied settings to these calls will override the default settings.

// settings will automatically be used by JsonConvert.SerializeObject/DeserializeObject
JsonConvert.DefaultSettings = () => new JsonSerializerSettings
    Formatting = Formatting.Indented,
    ContractResolver = new CamelCasePropertyNamesContractResolver()
Employee e = new Employee
    FirstName = "Eric",
    LastName = "Example",
    BirthDate = new DateTime(1980, 4, 20, 0, 0, 0, DateTimeKind.Utc),
    Department = "IT",
    JobTitle = "Web Dude"
string json = JsonConvert.SerializeObject(e);
// {
//   "firstName": "Eric",
//   "lastName": "Example",
//   "birthDate": "1980-04-20T00:00:00Z",
//   "department": "IT",
//   "jobTitle": "Web Dude"
// }

Because there are cases where JSON should not be customized, e.g. a Facebook or Twitter library, by default JsonSerializer won’t use DefaultSettings, providing an opt-out for those frameworks or for places in your application that shouldn’t use default settings. To create a JsonSerializer that does use them there is a new JsonSerializer.CreateDefault() method.

In the short term there will be some third party libraries that don’t use default settings that should, and some third party libraries that do use default settings that shouldn’t. If you encounter a situation where DefaultSettings doesn’t work for you then continue to customize Json.NET settings like you do today.

In the long term DefaultSettings will hopefully provide a simple, standard way to developers to customize JSON in .NET applications.

Extension Data

The second new feature in Json.NET 5.0 Release 5 is copied inspired by WCF’s IExtensibleDataObject.

Extension data is a JSON object’s values that aren’t matched to a .NET property during deserialization. By placing the JsonExtensionDataAttribute on a dictionary all unused values are automatically added to that dictionary and are accessible by you.

public class DirectoryAccount
  // normal deserialization
  public string DisplayName { get; set; }
  // these properties are set in OnDeserialized
  public string UserName { get; set; }
  public string Domain { get; set; }
  private IDictionary<string, JToken> _additionalData;
  private void OnDeserialized(StreamingContext context)
    // SAMAccountName is not deserialized to any property
    // and so it is added to the extension data dictionary
    string samAccountName = (string)_additionalData["SAMAccountName"];
    Domain = samAccountName.Split('\\')[0];
    UserName = samAccountName.Split('\\')[1];


Here is a complete list of what has changed since Json.NET 5.0 Release 4.

  • New feature – Added global default serialization settings with JsonConvert.DefaultSettings
  • New feature – Added extension data support with JsonExtensionDataAttribute
  • New feature – Added NullValueHandling and DefaultValueHandling support to serializing dynamic types
  • Change – Changed some explicit interface methods on JArray to public to support use with ImpromtuInterface
  • Fix – Fixed deserializing non-ISO formatted date dictionary keys
  • Fix – Fixed values not being set when deserializing with DefaultValueHandling.IgnoreAndPopulate
  • Fix – Fixed deserializing with type named handling and assemblies loaded with Assembly.LoadFrom
  • Fix - Fixed deserializing Regexes when using StringEnumConverter
  • Fix – Fixed serializing and deserializing typed DataSets


Json.NET CodePlex Project

Json.NET 5.0 Release 5 Download – Json.NET source code and assemblies

Json.NET 5.0 Release 4 – Performance

This release of Json.NET ships with many performance improvements, and is over 30% faster serializing and deserializing JSON compared to Json.NET 4.5.

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Json.NET extends its performance lead over DataContractJsonSerializer and continues to be significantly faster than JavaScriptSerializer which is used by ASP.NET MVC.

Compiled Expressions on Windows 8 and Windows Phone 8

An additional performance improvement specific to Windows 8 and Windows Phone 8 is the switch from the serializer internally using latebound reflection to compiled expressions. In exchange for a small one off cost the first time a type is serialized, compiled expressions are considerably faster than latebound reflection and provide an additional speed boost to Json.NET on Win8 and WP8.


Here is a complete list of what has changed since Json.NET 5.0 Release 1.

  • New feature - Added JsonWriter.SetWriteState to support inheritance from JsonWriter implementations
  • Change - Changed .NET 4.5 portable library and WinRT library to use compiled expressions reflection
  • Fix - Fixed error serializing non-generic types that implement IEnumerable<T>


Json.NET CodePlex Project

Json.NET 5.0 Release 4 Download – Json.NET source code and assemblies

Json.NET 5.0 Release 1 – .NET 4.5, BigInteger, Read-Only Collections

New and Updated Libraries

In Json.NET 5.0 there are a bunch of library version changes:

  • Added .NET 4.5 library
  • Added portable library targeting .NET 4.5 + WP8 + Win8
  • Removed the Silverlight library.
  • Removed the Windows Phone library

Upgrading library versions allows Json.NET to support new .NET features such as dynamic and async across more platforms.

A baseline portable class library still supports all platforms (.NET 4 + WP7 + SL5 + Win8) so have no fear  Silverlight and Windows Phone developers, even though the dedicated libraries have been removed you can continue use the latest version of Json.NET on Silverlight/Windows Phone with a portable class library.

Note that the assembly version number of Json.NET 5.0 hasn't changed and is still to avoid assembly redirect issues. Read more about assembly version numbers here.

Serializing NaN and Infinity Floating Point Values

Json.NET no longer serializes NaN and positive and negative infinity floating point values as symbols, which is invalid JSON. With 5.0 the new default is to serialize those values as strings, e.g. "NaN" instead of NaN. There is no change to serializing normal floating point numbers.

A FloatFormatHandling setting has been added so you can control how NaN and infinity values are serialized.

string json;
IList<double> d = new List<double> {1.1, double.NaN, double.PositiveInfinity};
json = JsonConvert.SerializeObject(d);
// [1.1,"NaN","Infinity"]
json = JsonConvert.SerializeObject(d, new JsonSerializerSettings {FloatFormatHandling = FloatFormatHandling.Symbol});
// [1.1,NaN,Infinity]
json = JsonConvert.SerializeObject(d, new JsonSerializerSettings {FloatFormatHandling = FloatFormatHandling.DefaultValue});
// [1.1,0.0,0.0]

BigInteger and Read-Only Collections

Json.NET 5.0 adds support for BigInteger. Now when reading and writing JSON there is no limit on the maximum size of integers Json.NET can handle.

There is also support for read-only collection interfaces (IReadOnlyList<T> and IReadOnlyDictionary<TKey, TValue>) which were added in .NET 4.5. As long as there is an IEnumerable<T> constructor then Json.NET will deserialize to the read-only collection for you.

string json = @"[
var l = JsonConvert.DeserializeObject<IReadOnlyList<BigInteger>>(json);
BigInteger nineQuindecillionAndOne = l[0];
// 9000000000000000000000000000000000000000000000001


There are many performance and memory improvements in Json.NET 5.0, especially when serializing and deserializing collections, and Json.NET in Windows 8 Store apps.


Here is a complete list of what has changed since Json.NET 4.5 Release 11.

  • New feature - Added .NET 4.5 library
  • New feature - Added portable library targeting .NET 4.5, Win8, WP8
  • New feature - Added Path to JToken
  • New feature - Added BigInteger support
  • New feature - Added IReadOnlyCollection<T> and IReadOnlyDictionary<TKey, TValue> support
  • New feature - Added FloatFormatHandling to JsonWriter/JsonSerializer/JsonSerializerSettings
  • New feature - Added DateFormatString to JsonWriter/JsonSerializer/JsonSerializerSettings
  • New feature - Added support for multiple serialization events and use base type serialization events
  • New feature - Added DeserializeAnonymousType overload with JsonSerializerSettings
  • New feature - Added support for specifying root type when serializing JSON with TypeNameHandling.Auto
  • New feature - Added support for creating lists and dictionaries with an IEnumerable<T> constructor
  • New feature - Added IConvertible support to JValue
  • New feature - Added support for serializing custom IConvertible values
  • New feature - Added support for deserializing IList
  • New feature - Added support for converting byte array JValues to Guid
  • New feature - Added support for deserializing byte arrays to Guid
  • Change - NaN and Infinity floating point values are serialized as strings by default
  • Change - Minor breaking changes to JsonSchema type
  • Change - Upgraded Windows Phone assembly to WP8
  • Change - DateTime IDictionary keys are now serialized in ISO date format
  • Change - DataContractAttribute is no longer inherited to match DataConctractSerializer behavior
  • Change - StringEnumConverter converts empty strings to null for nullable enums
  • Change - Guids serialize to a binary UUID in BSON instead of a string
  • Remove - Removed SL4 library
  • Remove - Removed WP7 library
  • Fix - Fixed JTokenWriter returning a null reference
  • Fix - Fixed static fields to no longer be included with fields serialization
  • Fix - Fixed recursively reading type wrapper objects when deserializing
  • Fix - Fixed incorrect namespace when converting XML to JSON
  • Fix - Fixed poor performance when serializing/deserialize dynamic objects
  • Fix - Fixed StringEnumConverter to throw JsonSerializerException on error
  • Fix - Fixed hidden properties not being serialized


Json.NET CodePlex Project

Json.NET 5.0 Release 1 Download – Json.NET source code and assemblies