JSON.NET : This 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, Silverlight, Windows Phone and Windows 8.