Windows Communication Foundation

Windows Communication Foundation (WCF) is Microsoft’s unified programming model for building service-oriented applications. It enables developers to build secure, reliable, transacted solutions that integrate across platforms and interoperate with existing investments.

What Is Windows Communication Foundation?
Now a days web services are used extensively for applications that are distributed across platforms and web services provide security, distributed transaction coordination and a reliable communication.
WCF simplifies webservice consumption and development through a Service Oriented Programming model. The typed programming model (called the service model) is designed to ease the development of distributed applications and to provide developers with expertise in ASP.NET Web services, .NET Framework remoting, and Enterprise Services, and who are coming to WCF with a familiar development experience.

Problem Example
The following example illustrates some of the problems that WCF addresses. A car rental company decides to create a new application for reserving cars. The creators of this rental car reservation application know that the business logic it implements must be accessible by other software running both inside and outside their company. Accordingly, they decide to build it in a service-oriented style, with the application’s logic exposed to other software through a well-defined set of services. To implement these services, and thus communicate with other software, the new application will use WCF.

Over its lifetime, the rental car reservation application will likely be accessed by a range of other applications. When it is designed, however, the architects of the rental car reservation application know that its business logic will be accessed, as shown in the preceding figure, by three other kinds of software:

A call center client application running on the Windows desktops that are used by employees in the organization’s call center. Created specifically for the new reservations system, this application will also be built using the Microsoft .NET Framework and WCF. This application is not truly distinct from the new rental car reservation application, because its only purpose is to act as a client for the new system. From a service-oriented perspective, it is just another client for the reservation system’s business logic.

An existing reservation application built on a J2EE server running on a non-Windows system. Due to a recent merger with another car rental firm, this existing system must be able to access the new application’s logic to provide customers of the merged firms with a unified experience.
Partner applications running on a variety of platforms, each located within a company that has a business arrangement with the car rental firm. Partners might include travel agencies, airlines, and others that have a business requirement to make car rental reservations.

The diverse communication requirements for the new rental car reservation application are not simple. For interactions with the call center client application, for instance, performance is important, while interoperability is straightforward, because both are built on the .NET Framework. For communication with the existing J2EE-based reservation application and with the diverse partner applications, however, interoperability becomes the highest goal. The security requirements are also quite different, varying across local Windows-based applications, a J2EE-based application running on another operating system, and a variety of partner applications coming in across the Internet. Even transactional requirements might vary, with only the internal applications being allowed to make transactional requests. How can these diverse business and technical requirements be met without exposing the creators of the new application to unmanageable complexity?
WCF is designed for this diverse but realistic scenario and is the default technology for Windows applications that expose and access services. This topic provides an introduction to WCF, examining what it provides and showing how it is used. Throughout this introduction, the scenario just described will serve as an example. The goal is to make clear what WCF is, show what problems it solves, and illustrate how it solves those problems.

The figure shows a view of a WCF client and service. The two interact using SOAP, the WCF native message representation, so even though the figure shows both parties built on WCF, this is not required. WCF is built on .NET Framework 2.0.

As the scenario described earlier suggests, WCF addresses a range of challenges for communicating applications. Three things stand out, however, as the most important aspects of WCF:

  • Unification of existing .NET Framework communication technologies like ASP.NET Web services (ASMX), .NET Framework remoting, Enterprise Services, WSE and Microsoft Message Queuing (MSMQ).
  • Support for cross-vendor interoperability, including reliability, security, and transactions.
  • Explicit service orientation.

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