Json.NET

http://www.newtonsoft.com/json
https://github.com/JamesNK/Newtonsoft.Json


Description:

Json.NET is a popular high-performance JSON framework for .NET

-Flexible JSON serializer for converting between .NET objects and JSON
-LINQ to JSON for manually reading and writing JSON
-High performance, faster than .NET's built-in JSON serializers
-Write indented, easy to read JSON
-Convert JSON to and from XML
-Supports .NET 2, .NET 3.5, .NET 4, .NET 4.5, Silverlight, Windows Phone and Windows 8 Store


Documentation:

http://www.newtonsoft.com/json/help/


Versions:

Json.NET has different libraries for the various .NET Framework versions.

-Net45:
  .NET latest (4.5)

-Net40:
  .NET 4.0

-Net35:
  .NET 3.5

-Net20:
  .NET 2.0, Unity

-Portable45:
  .NET 4.5, Windows Phone 8, Windows 8 Store, .NET Core

-Portable40:
  .NET 4.0, Windows Phone 8, Windows 8 Store, Silverlight 5, MonoTouch, MonoDroid


Notes:

For a Compact Framework 3.5 and Silverlight 3.0 builds download Json.NET 3.5
For a Silverlight 4.0 and Windows Phone 7 builds download Json.NET 5