poniedziałek, 12 grudnia 2016

70-487 [WCF] Create a WCF Service part 1

The first problem raised on the exam from WCF technology is Creating a WCF Service.
Here are the subtasks for the problem:
  • Create contracts (service, data, message callback, and fault);
  • Implement message inspectors;
  • Implement asynchronous operations in the service;
First let's start from question what WCF is?

The official book describes WCF as a runtime and corresponding set of application programming interfaces (APIs) that facilitate building distributed applications [1]. Another book defines WCF as component handling communication infrastructure of .NET 3.x and later, which allows to create a diverse range of applications through its simplified model [2]. Very often WCF services are part of Service Oriented Architectures (SOA). About SOA you can read more in [3].

For this exam you should be familiar with following SOA concepts and tenets:
  • Service - a component that is capable of performing one or more tasks,
  • Service definition - also known as a Contract, is a document that express meta information about a service,
  • Binding - item used to specify the transport, encoding, and protocol details require for a client and server to communicate with each other,
  • Serialization - transforms data from one representation to another so it can be transferred and consumed by different service,
  • Explicit boundaries - services should provide no visibility to the internal implementation of the service. This allows a services implementation to be versioned without breaking external systems,
  • Services are autonomous - the service and any items it contains must be independently deployed, versioned, and managed,
  • Services share schema and contract, not class - to communicate with a service, a client needs to know the uniform resource identifier (URI), the protocol the communication will happen with, and what operations are supported. It should not need a copy of the class or library that provides the operations,
  • Service compatibility is based on policy - at times you will not be able to express all the requirements of service interaction via WSDL alone; this is when you can use policies. Policy expressions essentially separate the structural and semantic compatibilities. In other words, they separate what is communicated from how/to whom a message is communicated.
In the next post we will decode acronym of WCF.

[1] Exam Ref 70-487: Developing Windows Azure and Web Services
[2] Pro WCF 4. Practical Microsoft SOA Implementation
[3] The OpenGroup "The SOA Book" http://www.opengroup.org/soa/source-book/soa/index.htm

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