What is a WCF Service?

Windows Communication Foundation (WCF) is a framework for building service-oriented applications. Using WCF, you can send data as asynchronous messages from one service endpoint to another. A service endpoint can be part of a continuously available service hosted by IIS, or it can be a service hosted in an application. An endpoint can be a client of a service that requests data from a service endpoint. The messages can be as simple as a single character or word sent as XML, or as complex as a stream of binary data. A few sample scenarios include:

• A secure service to process business transactions.
  
• A service that supplies current data to others, such as a traffic report or other monitoring service.
  
• A chat service that allows two people to communicate or exchange data in real time.
  
• A dashboard application that polls one or more services for data and presents it in a logical presentation.
  
• Exposing a workflow implemented using Windows Workflow Foundation as a WCF service.
  
• A Silverlight application to poll a service for the latest data feeds.

 Features of WCF

• Service Orientation
• Interoperability
• Multiple Message Patterns
• Service Metadata
• Data Contracts
• Security
• Multiple Transports and Encodings
• Reliable and Queued Messages
• Durable Messages
• Transactions
• AJAX and REST Support
• Extensibility

 WCF is a replacement for all earlier web service technologies from Microsoft. It also does a lot more than what is traditionally considered as "web services".

Messages can be sent on any of several built-in transport protocols and encodings. The most common protocol and encoding is to send text encoded SOAP messages using is the HyperText Transfer Protocol (HTTP) for use on the World Wide Web. Alternatively, WCF allows you to send messages over TCP, named pipes, or MSMQ. These messages can be encoded as text or using an optimized binary format. Binary data can be sent efficiently using the MTOM standard. If none of the provided transports or encodings suit your needs you can create your own custom transport or encoding.