Open Source C# JSON Serialization Libraries

RestSharp is probably the most popular HTTP client library for .NET. Featuring automatic serialization and deserialization, request and response type detection, variety of authentications and other useful features, it is being used by hundreds of thousands of projects. RestSharp passed over 32 million downloads on NuGet, with average daily download count of 10,000. It's being used by many popular OSS projects, including Roslyn and Swagger. The main purpose of RestSharp is to make synchronous and asynchronous calls to remote resources over HTTP. As the name suggests, the main audience of RestSharp are developers who use REST APIs. However, RestSharp can call any API over HTTP (but not HTTP/2), as long as you have the resource URI and request parameters that you want to send comply with W3C HTTP standards. RestSharp can take care of serializing the request body to JSON or XML and deserialize the response. It can also form a valid request URI based on different parameter kinds.

JSON data manipulation library, built for simplicity. Create JSON object from common data types (array, list and dictionary). Parser is based on regular expressions and can handle nested structures. Access data using implicit typecast. Tutorial with all examples included. For details visit Wiki section. New in v2.0.0: Added serialization and deserialization methods!!!

DynAjax is a Javascript / ASP.Net / C# Framework easing dynamic calls to business / service C# methods directly from JavaScript code (like DWR framework does in Java World). The object serialization is based on JSON, permitting complex objects exchange.