JSON.NET

Json - Release: Json.NET 3.5 Release 7

Json.NET library makes working with JSON formatted data in .NET simple. Key features include a flexible JSON serializer to for quickly converting .NET classes to JSON and back again, and LINQ to JSON for reading and writing JSON.

Features
-Flexible JSON serializer to convert .NET objects to JSON and back again
-LINQ to JSON for reading and writing JSON
-Writes indented, easy to read JSON
-Convert JSON to and from XML
-Supports Silverlight and the Compact Framework

The JSON serializer is a good choice when the JSON you are reading or writing maps closely to a .NET class. The serializer automatically reads and writes JSON for the class.

For situations where you are only interested in getting values from JSON, don't have a class to serialize or deserialize to, or the JSON is radically different from your class and you need to manually read and write from your objects then LINQ to JSON is what you should use. LINQ to JSON allows you to easily read, create and modify JSON in .NET.