Windows Communication Foundation in Framework 4.0

Windows Communication Foundation (WCF) provides the following improvements:

• Configuration-based activation: Removes the requirement for having an .svc file.
  
• System.Web.Routing integration: Gives you more control over your service’s URL by allowing the use of extensionless URLs.
• Multiple IIS site bindings support: Allows you to have multiple base addresses with the same protocol on the same Web site.
• Routing Service: Allows you to route messages based on content.
• Support for WS-Discovery: Allows you to create and search for discoverable services.
• Standard endpoints: Predefined endpoints that allow you to specify only certain properties.
• Workflow services: Integrates WCF and WF by providing activities to send and receive messages, the ability to correlate messages based on content, and a workflow service host.
• WCF REST features:
  • Web HTTP caching: Allows caching of Web HTTP service responses.
  • Web HTTP formats support: Allows you to dynamically determine the best format for a service operation to respond in.
  • Web HTTP services help page: Provides an automatic help page for Web HTTP services, similar to the WCF service help page.
  • Web HTTP error handling: Allows Web HTTP Services to return error information in the same format as the operation.
  • Web HTTP cross-domain JavaScript support: Allows use of JSON Padding (JSONP).
• Simplified configuration: Reduces the amount of configuration a service requires

WCF Architecture

The following figure illustrates the major components of WCF.

 
 

Contracts

Contracts layer are next to that of Application layer. Developer will directly use this contract to develop the service. We are also going to do the same now. Let us see briefly what these contracts will do for us and we will also know that WCF is working on message system.

Service contracts

– Describe about the operation that service can provide. Example, Service provided to know the temperature of the city based on the zip code, this service we call as Service contract. It will be created using Service and Operational Contract attribute.

Data contract

– It describes the custom data type which is exposed to the client. This defines the data types, are passed to and from service. Data types like int, string are identified by the client because it is already mention in XML schema definition language document, but custom created class or datatype cannot be identified by the client e.g. Employee data type. By using DataContract we can make client aware that we are using Employee data type for returning or passing parameter to the method.

Message Contract

– Default SOAP message format is provided by the WCF runtime for communication between Client and service. If it is not meeting your requirements then we can create our own message format. This can be achieved by using Message Contract attribute.

Policies and Binding

– Specify conditions required to communicate with a service e.g security requirement to communicate with service, protocol and encoding used for binding.

Service Runtime

– It contains the behaviors that occur during runtime of service.

• Throttling Behavior- Controls how many messages are processed.
  
• Error Behavior – Specifies what occurs, when internal error occurs on the service.
• Metadata Behavior – Tells how and whether metadata is available to outside world.
• Instance Behavior – Specifies how many instance of the service has to be created while running.
• Transaction Behavior – Enables the rollback of transacted operations if a failure occurs.
• Dispatch Behavior – Controls how a message is processed by the WCF Infrastructure.

Messaging

– Messaging layer is composed of channels. A channel is a component that processes a message in some way, for example, by authenticating a message. A set of channels is also known as a channel stack. Channels are the core abstraction for sending message to and receiving message from an Endpoint. Broadly we can categories channels as

• Transport Channels
  Handles sending and receiving message from network. Protocols like HTTP, TCP, name pipes and MSMQ.
  
• Protocol Channels
  Implements SOAP based protocol by processing and possibly modifying message. E.g. WS-Security and WS-Reliability.

Activation and Hosting

– Services can be hosted or executed, so that it will be available to everyone accessing from the client. WCF service can be hosted by following mechanism

• IIS
  Internet information Service provides number of advantages if a Service uses Http as protocol. It does not require Host code to activate the service, it automatically activates service code.
  
• Windows Activation Service
  (WAS) is the new process activation mechanism that ships with IIS 7.0. In addition to HTTP based communication, WCF can also use WAS to provide message-based activation over other protocols, such as TCP and named pipes.
• Self-Hosting
  WCF service can be self hosted as console application, Win Forms or WPF application with graphical UI.
• Windows Service
  WCF can also be hosted as a Windows Service, so that it is under control of the Service Control Manager (SCM).

Introducing $(document).ready()

This is the first thing to learn about jQuery: If you want an event to work on your page, you should call it inside the $(document).ready() function. Everything inside it will load as soon as the DOM is loaded and before the page contents are loaded.

$(document).ready(function() {
   // put all your jQuery goodness in here.
 });

The $(document).ready() function has a ton of advantages over other ways of getting events to work. First of all, you don’t have to put any “behavioral” markup in the HTML. You can separate all of your JavaScript/jQuery into a separate file where it’s easier to maintain and where it can stay out of the way of the content. I never did like seeing all those “javascript:void()” messages in the status bar when I would hover over a link. That’s what happens when you attach the event directly inside an <a href> tag.

On some pages that use traditional JavaScript, you’ll see an “onload” attribute in the <body> tag. The problem with this is that it’s limited to only one function. Oh yeah, and it adds “behavioral” markup to the content again. Jeremy Keith’s excellent book, DOM Scripting, showed me how to create an addLoadEvent function to a separate JavaScript file that allows for multiple functions to be loaded inside it. But it requires a fair amount of code for something that should be rather straightforward. Also, it triggers those events when the window loads, which leads me to another advantage of $(document).ready().

With $(document).ready(), you can get your events to load or fire or whatever you want them to do before the window loads. Everything that you stick inside its brackets is ready to go at the earliest possible moment — as soon as the DOM is registered by the browser, which allows for some nice hiding and showing effects and other stuff immediately when the user first sees the page elements.

Endpoints: Address, Bindings, and Contracts

WCF Service is a program that exposes a collection of Endpoints. Each Endpoint is a portal for communicating with the world.

All the WCF communications are take place through end point. End point consists of three components which are known as ‘ABC’: ‘A’ for Address, ‘B’ for Binding and ‘C’ for Contracts.

Address

Basically URL, specifies where this WCF service is hosted .Client will use this url to connect to the service. e.g

http://localhost/MyService/TestCalculator.svc

Binding

Binding will describes how client will communicate with service. There are different protocols available for the WCF to communicate to the Client. You can mention the protocol type based on your requirements.

A binding has several characteristics, including the following:

• Transport -Defines the base protocol to be used like HTTP, Named Pipes, TCP, and MSMQ are some type of protocols.
• Encoding (Optional) – Three types of encoding are available-Text, Binary, or Message Transmission Optimization Mechanism (MTOM). MTOM is an interoperable message format that allows the effective transmission of attachments or large messages (greater than 64K).
• Protocol(Optional) – Defines information to be used in the binding such as Security, transaction or reliable messaging capability

The following table gives some list of protocols supported by WCF binding.

Binding	Description
BasicHttpBinding	Basic Web service communication. No security by default
WSHttpBinding	Web services with WS-* support. Supports transactions
WSDualHttpBinding	Web services with duplex contract and transaction support
WSFederationHttpBinding	Web services with federated security. Supports transactions
MsmqIntegrationBinding	Communication directly with MSMQ applications. Supports transactions
NetMsmqBinding	Communication between WCF applications by using queuing. Supports transactions
NetNamedPipeBinding	Communication between WCF applications on same computer. Supports duplex contracts and transactions
NetPeerTcpBinding	Communication between computers across peer-to-peer services. Supports duplex contracts
NetTcpBinding	Communication between WCF applications across computers. Supports duplex contracts and transactions

Contract

Contracts specifies the info for how the service is implemented and what it offers. Collection of operation that specifies what the endpoint will communicate with outside world. Usually name of the Interface will be mentioned in the Contract, so the client application will be aware of the operations which are exposed to the client. Each operation is a simple exchange pattern such as one-way, duplex and request/reply.

Example:

Endpoints will be mentioned in the web.config file on the created service.

<system.serviceModel>
<services>
      <service
        behaviorConfiguration="TestServiceBehavior">
       <endpoint
         address="http://localhost/MyService/TestCalculator.svc" contract="ITestService"
          binding="wsHttpBinding"/>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior>
          <serviceMetadata httpGetEnabled="True"/>
          <serviceDebug includeExceptionDetailInFaults="true" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>