WCF - Windows Communication Foundation

Windows Communication Foundation (WCF) is Microsoft's programming model for using managed code to build unified Web services and other distributed systems that can communicate with each other. WCF focuses on connecting XML to programs that are built using development languages supported by Microsoft, such as VB.NET and C#. To support this cross-language communication, WCF uses the extensible Simple Object Access Protocol (SOAP). WCF is one of the four main products in Microsoft's .NET Framework 3.0, previously known as WinFX. The other three are the Windows Presentation Foundation, or WPF, the Windows Workflow Foundation, abbreviated as either WF or WinWF, and the Windows CardSpace. The .NET 3.0 suite is due to be released around the same time as Windows Vista, Microsoft's upcoming update to its Windows operating system. .NET 3.0 can also be used with Windows XP and Windows 2003 Server.

WCF includes the following set of features.

• Service Orientation
  
  One consequence of using WS standards is that WCF enables you to create service oriented applications. Service-oriented architecture (SOA) is the reliance on Web services to send and receive data.
  
  
• Interoperability
  
  WCF implements modern industry standards for Web service interoperability.
  
  
• Multiple Message Patterns
  
  Messages are exchanged in one of several patterns. The most common pattern is the request/reply pattern, where one endpoint requests data from a second endpoint. The second endpoint replies. There are other patterns such as a one-way message in which a single endpoint sends a message without any expectation of a reply.
  
  
• Service Metadata
  
  WCF supports publishing service metadata using formats specified in industry standards such as WSDL, XML Schema and WS-Policy. This metadata can be used to automatically generate and configure clients for accessing WCF services. Metadata can be published over HTTP and HTTPS or using the Web Service Metadata Exchange standard.
  
  
• Data Contracts
  
  Because WCF is built using the .NET Framework, it also includes code-friendly methods of supplying the contracts you want to enforce. One of the universal types of contracts is the data contract. In essence, as you code your service using Visual C# or Visual Basic, the easiest way to handle data is by creating classes that represent a data entity with properties that belong to the data entity.
  
  
• Security
  
  Messages can be encrypted to protect privacy and you can require users to authenticate themselves before being allowed to receive messages. Security can be implemented using well-known standards such as SSL or WS-SecureConversation.
  
  
• Multiple Transports and Encodings
  
  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.
  
  
• Reliable and Queued Messages
  
  WCF supports reliable message exchange using reliable sessions implemented over WS-Reliable Messaging and using MSMQ.
  
  
• Durable Messages
  
  A durable message is one that is never lost due to a disruption in the communication. The messages in a durable message pattern are always saved to a database. If a disruption occurs, the database allows you to resume the message exchange when the connection is restored.
  
  
• Transactions
  
  WCF also supports transactions using one of three transaction models: WS-AtomicTtransactions, the APIs in the System.Transactions namespace, and Microsoft Distributed Transaction Coordinator.
  
  
• AJAX and REST Support
  
  REST is an example of an evolving Web 2.0 technology. WCF can be configured to process "plain" XML data that is not wrapped in a SOAP envelope. WCF can also be extended to support specific XML formats, such as ATOM (a popular RSS standard), and even non-XML formats, such as JavaScript Object Notation (JSON).