WCF Architecture – Easy WCF
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WCF Architecture

In this article, we will discuss on WCF architecture.

WCF has a layered architecture.

It has application layer,Contracts, messaging and activation and hosting layer.

WCF Architecture

Contracts and Descriptions:


  • Contracts defines the  various service operations.
    • The data exchanged by a service with Client is defined by a data contract. Both the client and the service has to be in agreement with the data contract.
    • The message parameters are defined by XML Schema definition language (XSD) documents. The message contract defines message parts using SOAP protocols. A data contract is controlled by message contract.
    • The service contract specifies the actual method signatures of the service.
    • Policies and bindings defines the conditions required to communicate with a service.


Service Runtime:


  • The service runtime layer contains the runtime behaviors of actual operation of the service.
    • Throttling controls how many messages are processed.
    • An error behavior specifies what occurs when an internal error occurs on the service,
    • Metadata behavior governs how and whether metadata is made available to the outside world.
    • Instance behavior specifies how many instances of the service can be run
    • Transaction behavior enables the rollback of transacted operations if a failure occurs.
    • Dispatch behavior is the control of how a message is processed by the WCF infrastructure.
    • Extensibility enables customization of runtime processes.
    • Parameter filtering enables preset actions to occur based on filters acting on message headers.




  • The messaging layer is composed of channels.
    • A channel is a component that processes a message in some way . A set of channels is also known as a channel stack. Channels operate on messages and message headers.
  • There are two types of channels: transport channels and protocol channels.
    • Transport channels read and write messages from the network (or some other communication point with the outside world).
      • Examples of transports are HTTP, named pipes, TCP, and MSMQ. Examples of encodings are XML and optimized binary.
    • Protocol channels implement message processing protocols, often by reading or writing additional headers to the message.
      • Examples of such protocols include WS-Security and WS-Reliability.
  • The messaging layer supports the possible formats and exchange patterns of the data.
  • WS-Security is an implementation of the WS-Security specification enabling security at the message layer.
  • The WS-Reliable Messaging channel enables the guarantee of message delivery.
  • The encoders present a variety of encodings that can be used to suit the needs of the message.
  • The HTTP channel specifies that the HyperText Transport Protocol is used for message delivery.
  • The TCP channel similarly specifies the TCP protocol. The Transaction Flow channel governs transacted message patterns.
  • The Named Pipe channel enables interprocess communication.
  • The MSMQ channel enables interoperation with MSMQ applications.

Hosting and Activation:

  • A service must be run in an executable. This is known as a self-hosted service.
  • Services can also be hosted, or run in an executable managed by an external agent, such as IIS or Windows Activation Service (WAS).
  • WAS enables WCF applications to be activated automatically when deployed on a computer running WAS.
  • Services can also be manually run as executables (.exe files).
  • A service can also be run automatically as a Windows service.
  • COM+ components can also be hosted as WCF services


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