Windows Communication Foundation
The Windows Communication Foundation (or WCF), previously known as "Indigo", is a runtime and a set of APIs (application programming interface) in the .NET Framework for building connected, service-oriented applications.
WCF is a tool often used to implement and deploy a service-oriented architecture (SOA). It is designed using service oriented architecture principles to support distributed computing where services have remote consumers. Clients can consume multiple services; services can be consumed by multiple clients. Services are loosely coupled to each other. Services typically have a WSDL interface (Web Services Description Language) that any WCF client can use to consume the service, regardless of which platform the service is hosted on. WCF implements many advanced Web services (WS) standards such as WS-Addressing, WS-ReliableMessaging and WS-Security. With the release of .NET Framework 4.0, WCF also provides RSS Syndication Services, WS-Discovery, routing and better support for REST services.
EndpointsA WCF client connects to a WCF service via an Endpoint. Each service exposes its contract via one or more endpoints. An endpoint has an address (which is a URL specifying where the endpoint can be accessed) and binding properties that specify how the data will be transferred. The mnemonic "ABC" can be used to remember address / binding / Contract. Binding specifies what communication protocols are used to access the service, whether security mechanisms are to be used, and the like. WCF includes predefined bindings for most common communication protocols such as SOAP over HTTP, SOAP over TCP, and SOAP over Message Queues, etc. Interaction between WCF endpoint and client is done using a SOAP envelope. SOAP envelopes are in simple XML form, which makes WCF platform independent. When a client wants to access the service via an endpoint, it not only needs to know the contract, but it also has to adhere to the binding specified by the endpoint. Thus, both client and server must have compatible endpoints. With the release of the .NET Framework 3.5 in November 2007, Microsoft released an encoder that added support for the JSON serialization format to WCF. This allows WCF service endpoints to service requests from AJAX-powered Web pages which only accept JSON.
BehaviorsBehaviors are types that modify or extend service or client functionality. Behaviors allow the developer to create custom processing, transformation, or inspection that is applied to messages as they are sent or received. Some examples of uses for behaviors are:
- Controlling whether metadata is published with a service.
- Adding security features to a service, such as impersonation, authorization, or managing tokens
- Recording information about messages, such as tracking, tracing, or logging
- Message or parameter validation
- Invoking all additional operations when messages are received--such as notifying users when certain messages arrive
WCF supports interoperability with WCF applications running on the same Windows machine or WCF running on a different Windows machines or standard Web services built on platforms such as Java running on Windows or other operating systems. WCF does not support only SOAP messages, it can also be configured to support standard XML data that is not wrapped in SOAP, RSS, or JSON to make WCF support different requirements and future changes.