WCF is Microsoft platform for Service Oriented Architecture, enables applications to communicate whether they are on the same computer, across the Internet, or on different application platforms. In the distributed application development, we can use COM+, Web Services, Remoting, and Enterprise Services, MSMQ. All this technologies play different roles, and if we have to implement these technologies then developer have to concentrate each of these separate technologies and develop as separate solution.
But in WCF wraps all these technologies as one single Service Oriented Programming model, so that developers can concentrate on application logic rather than worrying about implementing communication protocols.
Advantage
1) We can have choices in choosing the Protocol, messaging formats and process allocation.
2) Supports core Web Service standards.
3) Extensible to quickly adapt to new protocol and updates.
The basic tasks to perform are, in order:
1) Define the service contract
2) Implement the contract
3) Configure the service
4) Host the service
5) Build a client application
Microsoft Technologies 