ASP.Net Web API 2.1 is the latest Microsoft technology which comes with ASP.Net MVC 4.0 onwards and it enables you to build restful, http-based services, which can be consumed by a variety of clients. In this guide you will learn step-by-step the techniques of using web api framework to create api services, it has lots of coding examples to explain the concepts and features of web api. It covers api controllers, api routing, data formats like json, xml, Bson and csv, api versioning, api controller action versioning, api hosting, controller unit testing, OData query support, authentication, authorization, and security.Web api 2.1, the latest version of web api, which has very sophisticated features for examples attribute routing which helps in api versioning, earlier versions had conventional routing only.The author is expert in Microsoft technologies and have been working in IT for last 17 years. He is hard core developer in Microsoft technologies.The guide is designed in such a manner so that you can learn the concepts and gain practical knowledge in the fastest possible manner.