Json.NET 3.5 Beta 1 – Big performance improvements, Compact Framework support and more

I am starting to get organised towards releasing Json.NET 3.5. There are a lot of good new features coming in this version, almost all of them driven by user requests.

Compact Framework Support

Json.NET 3.5 includes a build for the Compact Framework 3.5. It supports all the major features of Json.NET.

Performance Improvements

A lot of features have been added to Json.NET over the past couple of years and it has been a long time since I had done any performance tuning.

I busted out a profiler and found some big gains in the JsonSerializer by doing some basic caching of type data. I managed to eek out a 400% increase in performance. Not bad for 20 minutes work.

Below is a comparison of Json.NET 3.0, Json.NET 3.5 Beta 1, the WCF DataContractJsonSerializer and the JavaScriptSerializer. The code for the results is in the PerformanceTests class and is over 5000 iterations.

Okay Marge, its your child against my child. The winner will be showered with praise. The loser will be taunted and booed until my throat is sore.


There are a lot of settings on JsonSerializer but only a few of them are exposed through the JavaScriptConvert.SerializeObject/DeserializeObject helper methods. To make those options available through the easy to use helper methods I have added the JsonSerializerSettings class along with overloads using it to the helper methods.

public class Invoice
  public string Company { get; set; }
  public decimal Amount { get; set; }
  public bool Paid { get; set; }
  public DateTime? PaidDate { get; set; }

This example of the JsonSerializerSettings also shows another new feature of Json.NET 3.5: DefaultValueHandling. If the property value is the same as the default value then those values will be skipped when writing JSON.

public void SerializeInvoice()
  Invoice invoice = new Invoice
                      Company = "Acme Ltd.",
                      Amount = 50.0m,
                      Paid = false
  string json = JavaScriptConvert.SerializeObject(invoice);
  // {"Company":"Acme Ltd.","Amount":50.0,"Paid":false,"PaidDate":null}
  json = JavaScriptConvert.SerializeObject(invoice,
    new JsonSerializerSettings { DefaultValueHandling = DefaultValueHandling.Ignore });
  // {"Company":"Acme Ltd.","Amount":50.0}

Writing Raw JSON

For a long time JsonWriter has had a WriteRaw method. I can proudly say that now it actually works. Serializing raw JSON is also much improved with the new JsonRaw object.


Here is a complete list of what has changed.

  • New feature - Compact framework support
  • New feature - Big serializer performance improvements through caching of static type data
  • New feature - Added DefaultValueHandling option to JsonSerializer
  • New feature - JsonSerializer better supports deserializing into ICollection<T> objects
  • New feature - Added JsonSerializerSettings class along with overloads to JavaScriptConvert serialize/deserialize methods
  • New feature - IsoDateTimeConverter and JavaScriptDateTimeConverter now support nullable DateTimes
  • New feature - Added JsonWriter.WriteValue overloads for nullable types
  • New feature - Newtonsoft.Json.dll is now signed
  • New feature - Much better support for reading, writing and serializing raw JSON
  • New feature - Added JsonWriter.WriteRawValue
  • Change - Renamed Identifier to JsonRaw
  • Change - JSON date constructors deserialize to a date
  • Fix - JavaScriptConvert.DeserializeObject checks for addition content after deserializing an object
  • Fix - Changed JsonSerializer.Deserialize to take a TextReader instead of a StringReader
  • Fix - Changed JsonTextWriter.WriteValue(string) to write null instead of an empty string for a null value
  • Fix - JsonWriter.WriteValue(object) no longer errors on a null value
  • Fix - Corrected JContainer child ordering when adding multi values


Json.NET CodePlex Project

Json.NET 3.5 Beta 1 Download – Json.NET source code, documentation and binaries

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