Developing a REST Web Service using C# - A walkthrough

Objective

The objective of this article is to create a REST Web Service using C# which will support CRUD operations on the exposed object. This article concentrates on building the Web Service from scratch using HttpHandlers, and will give a detailed understanding of operations that happen “under the hood”. There are many documents which talk about REST Web Services, but hardly any which gives a complete code walkthrough. This is just what I intend to do. In subsequent releases, we will see how in-built project templates can be used to achieve the same objective.

Introduction

REST stands for Representational State Transfer. The term was introduced by Roy Fielding in his doctorial dissertation. REST is an architectural style for designing networked applications. It is an alternate to using complex mechanisms like COBRA, RPC, and SOAP to connect between client and server. REST makes communication between remote computers easy by using the simple HTTP protocol which support for CRUD (Create, Read, Update, and Delete) operations on the server. In a way, our World Wide Web is also based on the REST architecture.

In a nutshell, REST is based on the representation of resources. A resource is an object that we can access over the World Wide Web. It can be a document, an image, or anything. When we request a resource (an object) from a server, the server returns the representation of that resource. In REST architecture, a client requests an operation (CRUD) on an object (resource) on the server, and the server returns data as per requirements.

Example – Let us consider a Web Service that returns Employee information. The Web Service responds to client calls by polling a database and returning a result. In classical Web Services or WCF Services, we would have a method exposed to clients, like GetEmployee(). The REST architecture is different from this as it does not work with the methods but with nouns (resources / objects) and allow verbs (HTTP Methods) to operate on them.

So if we want to get Employee information, we send an HTTP GET on the object Employee rather than query a method like GetEmployee(). The advantage is manifold, the most important being the power and flexibility that we get in our hands to play around with the object.

For further reading, see the References section at the end of the article. I will not go into the details of explaining REST, rather concentrate on how to code one from scratch.

Why use REST?

Let us consider a practical example. Imagine that you have to build a Web Service which should be cross functional and should be able to be consumed by any client. Traditional Web Services in .NET have to be consumed using a proxy. What if the client does not know how to create a proxy? Imagine that your Web Service needs to be consumed by a client running on an iPhone or Android. As far as I know, Objective C does not know how to create a proxy. It only knows to send basic HTTP verbs – GET, PUT, POST, and DELETE – to the server and expect XML or string as response. Enter the world of REST!!

Read more: Codeproject

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