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Introduction to WCF Services

1

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2Introduction to WCF Services / Session 1

Objectives

Describe Windows Communication Foundation (WCF)

and service-oriented development with WCF

Explain the procedure to create and host a WCF service

using Visual Studio 2008

Explain the procedure to consume a WCF service usingVisual Studio 2008

Describe programmatic configuration of applications to

host and call a WCF service

Explain deployment of WCF services

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Service Oriented Architecture (SOA):

Is an approach to create enterprise applications

Integrates existing business components

Exposes the application to your business partners

Addresses and accommodates changes easily Helps heterogeneous platforms and applications

communicate with each other

Exposes the logic of an application as a service

without letting others know about the actual code

Introduction to WCF Services / Session 1 3

Introduction

3

Real World Example of SOA-based application

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SOA

In SOA:

The server machine or the server program hosts the

code

The server machine or the server program exposes

the code to the clients as a service

Any enterprise application is built using the three

building blocks:

Code

Server Program Client Program

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Windows Communication Foundation (WCF)

WCF:

Is an important part of the Microsoft .NET Framework architecture Is a SOA-based technology to create distributed enterprise applications

Includes features like multiple protocol support, reliability, and security

Offers interoperability with other services

WCF key components include:

Service Class

WCF Runtime

Host Application

Service class is the actual business logic exposed as a WCF service

WCF runtime serves any class as a WCF service

The class should implement an interface with the ServiceContract

attribute

Host application hosts the WCF runtime

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WCF Architecture 1-3

The following figure shows the WCF architecture:

6

The architecture includes:

A service host application

A client application

The service host application hosts a service class through multiple

endpoints

This service class will be exposed as a WCF service

The host application hosts the WCF runtime The client application communicates with the server application

through the proxy class

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A dispatcher component:

Is a helper component

Acts as if it is a client on the server machine and takes the service request

Passes the reply of the server to the channel next to it. The message is

passed through a series of channels, till it reaches the client

Channels:

Are processing units

Are inbuilt components of WCF

Exist on a client and the server to process input or output message

Address is the URL at which the server provides the service

Binding describes how the client communicates with the service

Contract describes the functionality provided by the service

Endpoint:

Specifies the following:

How to host a service class on the server

application

The protocol to be used for communication



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Is a combination of address, binding, and contract

Commonly referred as ABC

Information can be specified in the code and configuration file

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The WCF runtime exposes any class as a WCF service class

provided: The class implements an interface with the

ServiceContractattribute

The WCF runtime exposes a method declared in an interface

only with theOperationContract

attribute

The client application talks to the service application through

the proxy class

The client can choose to interact with the interface directly

instead of using the proxy class In the figure, the proxy class:

Forms a message on behalf of the client application

Passes the message on to the server

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Describing the WCF Service

The WCF runtime:

Exposes and controls a class as the WCF service Is represented in the System.ServiceModelnamespace that

resides inside the System.ServiceModel.dlllibrary

Is hosted in the host process that acts as a server application

This server application can be:

The EXE assemblies created using the console-based application,

Windows-based application, and Windows service

IIS or Windows Activation Service

The WCF service class hosted in an application other than IIS

is called self-hosted WCF service

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Creating and Hosting a WCF Service using Visual Studio 2008

To create and host a WCF service in Visual Studio

2008, you need to create a:

Service interface

Service class

Server alias host application

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The service interface describes the functionality offered

by the server:

Creating a Service Interface 1-2

namespace

{[ServiceContract]

public interface

{

[OperationContract]

(Parameters );

[OperationContract]

(Parameters );

. .

. .

}

}

Syntax


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Creating a Service Interface 2-2

namespace MyService

{

[ServiceContract]

public interface IHello

{

[OperationContract]

string SayHello(string inputMessage);

}

}

Snippet


In order to use the code, you need to import the

System.ServiceModelnamespace from

System.ServiceModel.dll

The code shows a simple IHelloservice interface:

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A service class implements the functionality declared in the service interface:

Creating a Service Class 1-2

namespace

{

public class:

{

public (Parameters)

{

// Actual functionality related code

return ;

}

public (Parameters)

{// Actual functionality related code

return ;

}

}

}

Syntax


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In the code, the service class, HelloService, implements the

IHelloServiceinterface:

Creating a Service Class 2-2

namespace MyService

{

public class HelloService: IHello

{

public string SayHello(string inputMessage)

{

return "Hello " + inputMessage;

}

}

}

Snippet


In order to use the code, you need to import the System.ServiceModel

namespace from System.ServiceModel.dll

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Creating a Server or Host Application 1-7

After creating the service class, you need to create a host application

You can host the WCF service class on: IIS

Custom host application

You need to specify the Address, Binding and Contract (ABC) information

Generally, ABC information is written in XML-based configuration files If the service class is IIS hosted, then the host application uses web.config

file

If the service class is self-hosted, then the host application uses app.config

file

The host application needs to know the following: Which service interface functionality should be offered to the client?

Which protocol should be used?

What is the information regarding input/output parameters?

How to start listening requests from the client applications?

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The syntax for the configuration file is as follows:



Syntax

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address=http://localhost:9898/HelloService informs the WCF runtimethat the client will communicate and ask forHelloServiceat the port number 9898.

binding="basicHttpBinding"informs the WCF runtime that the HTTPprotocol with no security needs to be usedfor communication



Snippet

informs the WCF runtime that the

MyService.HelloService class needs to beexposed as a WCF service

contract="MyService.IHello"

informs the WCF runtime that only the

MyService.IHellokind of

functionality needs to be exposed fromthe MyService.HelloService

class

The following code shows a sample code inside theapp.config file

To use the code, you need to reference

System.ServiceModel.dll

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Consider a console application as a server

application This means that you are hosting the WCF service on

your own server, that is, the console application

This refers to self-hosting

Consider that this server listens to the client

requests for the HelloServiceWCF service

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The code shows how the server listens to the client requests

Note that this code should be written inside the main method ofthe server

ServiceHost host = new

ServiceHost(typeof(MyService.HelloService));host.Open();

Snippet


In order to use the code, you need to import the

System.ServiceModelnamespace fromSystem.ServiceModel.dll

In the code, a call to Open()method creates and opens the

listener for the service


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In the IIS-hosted WCF service, the ServiceHost

object used in the previous code is replaced with a filethat has the extension .SVC

A directive called @ServiceHost represents the

entire code The syntax to use the @ServiceHost directive in the

.SVC file is as follows:

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You can call the WCF service functionality hosted on the server

using:

The service interface in combination with a mediator

The mediator communicates on behalf of the client with the

service that is represented by a class called ChannelFactory

The Service Reference option in Visual Studio

The SVCUTIL.EXE utility that ships with the .NET framework

When you use the SVCUTIL.EXE utility or the Service Reference

option, a proxy class is created

To share only the interface library with the client, you can usethe ChannelFactoryclass


Consuming the WCF service using Visual Studio 2008

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To access a WCF service hosted on the server by using

ChannelFactory:

In the client application, add a reference to the service

interface library

Add app.config configuration file in the client

application


ChannelFactory 1-5

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The syntax adds the client-side app.config configuration file:

Syntax


ChannelFactory 2-5

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The syntax to use the service interface and create an object is as

follows:

= new ChannelFactory("").CreateChannel();

Syntax


ChannelFactory 4-5

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The code shows how to use ChannelFactoryto call the

HelloServiceWCF service

You need to import the System.ServiceModelnamespace

from System.ServiceModel.dll

IHello obj = new ChannelFactory("MyEndPoint").CreateChannel();

Console.WriteLine(obj.SayHello("WCF"));

Snippet


ChannelFactory 5-5

Call the CreateChannel()method

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To access the WCF service hosted on the server by

using the Service Reference option in Visual Studio,

follow these steps:

1. Ensure that the server application is running

2. In the client application, in the Solution Explorer window, right-click Referencesand click Add Service Reference. The AddService Reference window is displayed

3. To call the service, in the Addresstext box, type the URL

4. To hold the proxy class, in the Namespacetextbox, type thenamespace name

5. To add the proxy, click OK6. Create a proxy class object and call the Web method


The Service Reference Option

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To create a proxy class and access the WCF service

using the SVCUTIL.EXEutility, perform the following

steps:1. Ensure the server application is running

2. Click StartProgramsMicrosoft Visual Studio 2008 VisualStudio ToolsVisual Studio 2008 Command Prompt

3. Use the following syntax to use the SVCUTIL.EXE utility

The code shows how to use the SVCUTIL command to

generate the proxy class and the configuration file forHelloServiceWCF service


Using the SVCUTIL.EXE Utility 1-2

Syntax

SVCUTIL /Config:App.Config /Out:

Snippet

SVCUTIL /Config:App.Config /Out:proxy.cshttp://localhost:9898/HelloService

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4. Press Enter. This generates two files, the proxy class file and the

app.config configuration file

5. Add the generated files, the proxy class file and the app.config file

to the client application

6. Call the WCF service using the proxy class object (generated in Step4)


Using the SVCUTIL.EXE Utility 2-2

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The following figure displays different types of host applications

host a WCF service:


Deploying a WCF Service 1-2

IIS 6.0 only supports HTTP protocol

IIS 7.0 supports TCP and HTTP

protocols

The service hosted using the following

is called the self-hosted WCF service:

Windows application

Console application

Windows service

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The table shows various hosting environments and the

protocols that each environment supports:


Deploying a WCF Service 2-2

Hosting Environment Supported Protocols

Windows or Console application HTTP, net.tcp, net.pipe, net.msmq

Windows service application HTTP, net.tcp, net.pipe, net.msmq

Web Server IIS6 HTTP

Web Server IIS7 - Windows Process

Activation Service (WAS)

HTTP, net.tcp, net.pipe, net.msmq

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Summary

WCF is a SOA-based technology from Microsoft for distributed enterprise

application development

A WCF service class implements an interface with the

[ServiceContract]attribute and exposes the methods with the

[OperationContract]attribute

The server application hosts a WCF service class and offers the functionality of

the class as a service to the clients

WCF services can be self-hosted or IIS hosted

A client determines the functionality offered by the server using the interface

or the proxy class

A client requests the functionality from a WCF service using the

ChannelFactoryclass, the proxy class, or the SVCUTIL.EXE utility The client and server configuration can be written either in code or in

configuration files

Documents

Session 1_23.ppt