Json.NET

Json.NET is a powerful framework for the .NET  environment that allows object serialization, providing fast processing speed and XML support.
Aiming to provide versatility and address all user requirements, Json.NET deploys components for various versions of the .NET Framework, namely .NET 2, .NET 3.5, .NET 4, and .NET 4.5, as well as support for Windows 8 Store, Windows Phone, Mono, Xamarin, and Silverlight.
The integrated JSON serializer makes it possible for developers to conveniently convert between .NET objects and JSON, offering higher speeds than other similar development tools. Json.NET also provides support for BSON, JSON Schema, also providing  serialization of circular references and multidimensional arrays. Additional attributes, such as JsonIgnore and JsonProperty, can be assigned to a class to define serialization options.
Thanks to the integrated JObject, JValue, and JArray components, you can use Json.NET to create, modify, and parse JSON formatted data. JSON Path enables developers to run queries in JSON with a simple syntax.
Furthermore, the JsonReader and JsonWriter libraries allow you to read and write such data, so you can generate JSON data either for display or debugging. If required, Json.NET can easily convert JSON data to XML format and vice-versa.
The popularity of Json.NET has grown over time and now it is used in various open-source projects, such as Mono, RavenDB, ASP.NET SignalR, or ASP.NET Web API.