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. The architecture 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.
Endpoints
A 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.
Behaviors
Behaviours are just 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
Behaviors implement the
IServiceBehavior interface for service
extensions, the IEndpointBehavior
for endpoints, the
IContractBehavior interface for
service contracts, or the
IOperationBehavior for operations.
Service behaviors are used for message
processing across a service, rather than
processing that would be specific to a
single operation.
Interoperability
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. In addition to SOAP, WCF 4
supports non-SOAP XML, RSS, JSON , and
binary formats for external communication
via HTTP or HTTPS.
