Introduction to WCF Services1
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 using Visual Studio 2008
Describe programmatic configuration of applications to host and call a WCF service
Explain deployment of WCF services
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
Introduction to WCF Services / Session 1 4
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
4
Introduction to WCF Services / Session 1 5
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
5
Introduction to WCF Services / Session 1 6
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
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
Introduction to WCF Services / Session 1 7
WCF Architecture 2-3
7
Is a combination of address, binding, and contract Commonly referred as ABC
Information can be specified in the code and configuration file
Introduction to WCF Services / Session 1 8
WCF Architecture 3-3
The WCF runtime exposes any class as a WCF service class provided:
The class implements an interface with the ServiceContract attribute
The WCF runtime exposes a method declared in an interface only with the OperationContract 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
8
Introduction to WCF Services / Session 1 9
Describing the WCF Service
The WCF runtime: Exposes and controls a class as the WCF service Is represented in the System.ServiceModel namespace that
resides inside the System.ServiceModel.dll library 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
9
Introduction to WCF Services / Session 1 10
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
10
The service interface describes the functionality offered by the server:
Creating a Service Interface 1-2
namespace <namespace Name>
{
[ServiceContract]
public interface <interface Name>
{
[OperationContract]
<return type><Function Name> (Parameters …);
[OperationContract]
<return type><Function Name> (Parameters …);
. .
. .
}
}
Syntax
11Introduction to WCF Services / Session 1
Creating a Service Interface 2-2
namespace MyService
{
[ServiceContract]
public interface IHello
{
[OperationContract]
string SayHello(string inputMessage);
}
}
Snippet
12Introduction to WCF Services / Session 1
In order to use the code, you need to import the System.ServiceModel namespace from System.ServiceModel.dll
The code shows a simple IHello service interface:
A service class implements the functionality declared in the service interface:
Creating a Service Class 1-2
namespace <namespace Name>
{
public class<class Name>:<interface Name>
{
public <return type><Function Name> (Parameters)
{
// Actual functionality related code
return <return value>;
}
public <return type><Function Name> (Parameters)
{
// Actual functionality related code
return <return value>;
}
}
}
Syntax
13Introduction to WCF Services / Session 1
In the code, the service class, HelloService, implements the IHelloService interface:
Creating a Service Class 2-2
namespace MyService
{
public class HelloService: IHello
{
public string SayHello(string inputMessage)
{
return "Hello " + inputMessage;
}
}
}
Snippet
14Introduction to WCF Services / Session 1
In order to use the code, you need to import the System.ServiceModel namespace from System.ServiceModel.dll
Introduction to WCF Services / Session 1 15
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?
15
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.serviceModel>
<services>
<service name="<Fully Qualified Name of the Service Class>">
<endpoint
address="<URI where the service needs to accessed>"
binding="<way how service needs to be accessed>"
contract="<Fully Qualified Name of the Interface – defines what is offered from the service>"/>
<other endpoints>
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior>
<serviceMetadata httpGetEnabled="true"/>
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>
</configuration>
The syntax for the configuration file is as follows:
16Introduction to WCF Services / Session 1
Creating a Server or Host Application 2-7
Syntax
<?xml version="1.0"?>
<configuration>
<system.serviceModel>
<services>
<service name="MyService.HelloService">
<endpoint address="http://localhost:9898/HelloService"
binding="basicHttpBinding"
contract="MyService.IHello"/>
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior>
<serviceMetadata httpGetEnabled="true"/>
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>
</configuration>
address=http://localhost:9898/HelloService
informs the WCF runtime that the client will communicate and ask for HelloService
at the port number 9898.
binding="basicHttpBinding" informs the WCF runtime that the HTTP protocol with no security needs to be used for communication
17Introduction to WCF Services / Session 1
Creating a Server or Host Application 3-7 Snippe
t<service name="MyService.HelloService">
informs the WCF runtime that the MyService.HelloService class needs to be exposed as a WCF service
contract="MyService.IHello" informs the WCF runtime that only the MyService.IHello kind of functionality needs to be exposed from the MyService.HelloService class
The following code shows a sample code inside the app.config file
To use the code, you need to reference System.ServiceModel.dll
Introduction to WCF Services / Session 1 18
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 HelloService WCF service
18
Creating a Server or Host Application 4-7
The code shows how the server listens to the client requests
Note that this code should be written inside the main method of the server
ServiceHost host = new ServiceHost(typeof(MyService.HelloService));
host.Open();
Snippet
19Introduction to WCF Services / Session 1
In order to use the code, you need to import the System.ServiceModel namespace from System.ServiceModel.dll
In the code, a call to Open() method creates and opens the listener for the service
Creating a Server or Host Application 5-7
In the IIS-hosted WCF service, the ServiceHost object used in the previous code is replaced with a file that 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:
<%@ ServiceHost Language=”C#” Service=”<name of service class which implements functionality >" CodeBehind="<File which contains service class>" %>
Syntax
20Introduction to WCF Services / Session 1
Creating a Server or Host Application 6-7
The code shows a @ServiceHost directive in the HelloService.SVC file while you host MyService.HelloService
To use the code, you need to add the reference to System.ServiceModel.dll
<%@ ServiceHost Language="C#" Debug="true" Service="MyService.HelloService" CodeBehind="HelloService.svc.cs" %>
Snippet
21Introduction to WCF Services / Session 1
Creating a Server or Host Application 7-7
The Service property informs the WCF runtime that when a call is given to the HelloService.SVC file, it should create an object of the MyService.HelloService class and serve it to the client
The CodeBehind property informs the WCF runtime about the file in which the MyService.HelloService class is defined
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 use the ChannelFactory class
22Introduction to WCF Services / Session 1
Consuming the WCF service using Visual Studio 2008
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
23Introduction to WCF Services / Session 1
ChannelFactory 1-5
The syntax adds the client-side app.config configuration file:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.serviceModel>
<client>
<endpoint
address="<URI where the service needs to accessed>"
binding="<way how service needs to be accessed>"
contract="<Fully Qualified Name of the Interface – defines what
is offered from the service>"
name="<Name_For_the_Configuration>"/>
</client>
</system.serviceModel>
</configuration>
Syntax
24Introduction to WCF Services / Session 1
ChannelFactory 2-5
The code shows the code in the app.config configuration file for the HelloService WCF service:
<?xml version="1.0"?>
<configuration>
<system.serviceModel>
<client>
<endpoint address="http://localhost:9898/HelloService"
binding="basicHttpBinding"
contract="MyService.IHello"
name="MyEndPoint"/>
</client>
</system.serviceModel>
</configuration>
Snippet
25Introduction to WCF Services / Session 1
ChannelFactory 3-5
The syntax to use the service interface and create an object is as follows:
<Interfacereference>= new ChannelFactory<Interface Type>("<Name_For_the_Configuration>").CreateChannel();
Syntax
26Introduction to WCF Services / Session 1
ChannelFactory 4-5
The code shows how to use ChannelFactory to call the HelloService WCF service
You need to import the System.ServiceModel namespace from System.ServiceModel.dll
IHello obj = new ChannelFactory<IHello>(" MyEndPoint").CreateChannel();
Console.WriteLine(obj.SayHello("WCF"));
Snippet
27Introduction to WCF Services / Session 1
ChannelFactory 5-5
Call the CreateChannel() method
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 running2. In the client application, in the Solution Explorer window, right-
click References and click Add Service Reference. The Add Service Reference window is displayed
3. To call the service, in the Address text box, type the URL4. To hold the proxy class, in the Namespace textbox, type the
namespace name5. To add the proxy, click OK6. Create a proxy class object and call the Web method
28Introduction to WCF Services / Session 1
The Service Reference Option
To create a proxy class and access the WCF service using the SVCUTIL.EXE utility, perform the following steps:
1. Ensure the server application is running2. Click Start Programs Microsoft Visual Studio 2008 Visual
Studio Tools Visual Studio 2008 Command Prompt3. 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 for HelloService WCF service
29Introduction to WCF Services / Session 1
Using the SVCUTIL.EXE Utility 1-2
Syntax
SVCUTIL /Config:App.Config /Out:<Proxy Class File Name> “<type the URL with which the service can be called >”
Snippet
SVCUTIL /Config:App.Config /Out:proxy.cs “http://localhost:9898/HelloService”
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 Step 4)
30Introduction to WCF Services / Session 1
Using the SVCUTIL.EXE Utility 2-2
The following figure displays different types of host applications host a WCF service:
31Introduction to WCF Services / Session 1
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
The table shows various hosting environments and the protocols that each environment supports:
32Introduction to WCF Services / Session 1
Deploying a WCF Service 2-2
Hosting Environment Supported ProtocolsWindows or Console application HTTP, net.tcp, net.pipe,
net.msmqWindows service application HTTP, net.tcp, net.pipe,
net.msmqWeb Server IIS6 HTTPWeb Server IIS7 - Windows Process Activation Service (WAS)
HTTP, net.tcp, net.pipe, net.msmq
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
ChannelFactory class, the proxy class, or the SVCUTIL.EXE utility The client and server configuration can be written either in code or in
configuration files
33Introduction to WCF Services / Session 1