WCF

                     Windows Communication Foundation

Windows Communication Foundation (Code named Indigo) is a programming platform and runtime system for building, configuring and deploying network-distributed services. It is the latest service oriented technology; Interoperability is the fundamental characteristics of WCF. It is unified programming model provided in .Net Framework 3.0 WCF is a combined features of Web Service, Remoting, MSMQ and COM+. WCF provides a common platform for all .NET communication.

Definition:

Windows Communication Foundation (WCF) is a framework for building service-oriented applications. Using WCF we can build secure, reliable, transacted solutions that integrate across platforms.

Below figures shows the different technology combined to form WCF.

Advantage

1. WCF is interoperable with other services when compared to .Net Remoting,where the client and service have to be .Net.
2. WCF services provide better reliability and security in compared to ASMX web services.
3. In WCF, there is no need to make much change in code for implementing the security model and changing the binding. Small changes in the configuration will make your requirements.
4. WCF has integrated logging mechanism, changing the configuration file settings will provide this functionality. In other technology developer has to write the code.

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).

Features of WCF:

1.      Service Orientation

2.      Interoperability

3.      Multiple Message Patterns

4.      Service Metadata

5.      Data Contracts

6.      Security

7.      Multiple Transports and Encodings

8.      Reliable and Queued Messages

9.      Durable Messages

10.  Transactions

11.  AJAX and REST Support

12.  Extensibility

Terms of WCF:

 A WCF service is exposed to the outside world as a collection of endpoints.       

1. Endpoint: Endpoint is a construct at which messages are sent or received (or both). Endpoint comprises of ABC’s

What are ABC’s of WCF ? 

A. Address - Address is a location that defines where messages can be sent

B. Binding - Binding is a specification of the communication mechanism (a binding) that described how messages should be sent

 The endpoints also define a binding that specifies how a client will communicate with the service and the address where the endpoint is hosted. Various components of the WCF are depicted in the figure below.

·         "A" stands for Address: Where is the service?

·         "B" stands for Binding: How can we talk to the service?

·         "C" stands for Contract: What can the service do for us?

Different bindings supported by WCF

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
BasicHttpBinding	Basic Web service communication. No security by default
WSHttpBinding	Web services with WS-* support. Supports transactions

C. Contract - Contract is a definition for a set of messages that can be sent or received (or both) at that location (a service contract) that describes what message can be sent.

2. Service: A construct that exposes one or more endpoints, with each endpoint exposing one or more service operations.

3. Contracts: A contract is a agreement between two or more parties for common understanding and it is a is a platform-neutral and standard way of describing what the service does. In WCF, all services expose contracts.

Types of Contracts:
1) Operation Contract: An operation contract defines the parameters and return type of an operation.

1	[OperationContract]
2	double Add(double i, double j);

2) Service Contract: Ties together multiple related operations contracts into a single functional unit.

01	[ServiceContract] //System.ServiceModel
02	public interface IMath

03	{
04	[OperationContract]

05	double Add(double i, double j);
06	[OperationContract]

07	double Sub(double i, double j);
08	[OperationContract]

09	Complex AddComplexNo(Complex i, Complex j);
10	[OperationContract]

11	Complex SubComplexNo(Complex i, Complex j);
12	}

3) Data Contract: The descriptions in metadata of the data types that a service uses.

01	// Use a data contract
02	[DataContract] //using System.Runtime.Serialization

03	public class Complex
04	{

05	private int real;
06	private int imaginary;

07
08	[DataMember]

09	public int Real { get; set; }
10

11	[DataMember]
12	public int Imaginary { get; set; }

13

}

Difference between WCF and Web service

Web service is a part of WCF. WCF offers much more flexibility and portability to develop a service when comparing to web service. Still we are having more advantages over Web service, following table provides detailed difference between them.

Features	Web Service	WCF
Hosting	It can be hosted in IIS	It can be hosted in IIS, windows activation service, Self-hosting, Windows service
Programming	[WebService] attribute has to be added to the class	[ServiceContraact] attribute has to be added to the class
Model	[WebMethod] attribute represents the method exposed to client	[OperationContract] attribute represents the method exposed to client
Operation	One-way, Request- Response are the different operations supported in web service	One-Way, Request-Response, Duplex are different type of operations supported in WCF
XML	System.Xml.serialization name space is used for serialization	System.Runtime.Serialization namespace is used for serialization
Encoding	XML 1.0, MTOM(Message Transmission Optimization Mechanism), DIME, Custom	XML 1.0, MTOM, Binary, Custom
Transports	Can be accessed through HTTP, TCP, Custom	Can be accessed through HTTP, TCP, Named pipes, MSMQ,P2P, Custom
Protocols	Security	Security, Reliable messaging, Transactions

 WCF  Examples:

This is the Basic WCF Tutorial ‘wcfMathSerLib’ will be created in a step by step approach. This ‘wcfMathSerLib’ will be tested by ‘ConsoleMathClient’ and with ‘WCF Test Client’

Steps for creating wcfMathSerLib

1. Open Visual Studio 2010 and File->NewProject
2.select WCF in ‘Recent Templates’
3.select ‘WCF Service Library’
4.Give Name as wcfMathServiceLibrary
5.Click OK

2. Delete IService1.cs and Service1.cs

3. Add IMath.cs and MathService.cs and add the code listed below

IMath.cs

01	using System.Runtime.Serialization;
02	using System.ServiceModel;

03
04	namespace WcfMathServLib

05	{
06	[ServiceContract] //System.ServiceModel

07	public interface IMath
08	{

09	[OperationContract]
10	double Add(double i, double j);

11	[OperationContract]
12	double Sub(double i, double j);

13	[OperationContract]
14	Complex AddComplexNo(Complex i, Complex j);

15	[OperationContract]
16	Complex SubComplexNo(Complex i, Complex j);

17	}
18

19	// Use a data contract
20	[DataContract] //using System.Runtime.Serialization

21	public class Complex
22	{

23	private int real;
24	private int imaginary;

25
26	[DataMember]

27	public int Real { get; set; }
28

29	[DataMember]
30	public int Imaginary { get; set; }

31	}
32	}

MathService.cs

01	namespace WcfMathServLib
02	{

03	public class MathService : IMath
04	{

05
06	public double Add(double i, double j)

07	{
08	return (i + j);

09	}
10

11	public double Sub(double i, double j)
12	{

13	return (i - j);
14	}

15
16	public Complex AddComplexNo(Complex i, Complex j)

17	{
18	Complex result = new Complex();

19	result.Real = i.Real + j.Real;
20	result.Imaginary = i.Imaginary + j.Imaginary;

21	return result;
22	}

23
24	public Complex SubComplexNo(Complex i, Complex j)

25	{
26	Complex result = new Complex();

27	result.Real = i.Real - j.Real;
28	result.Imaginary = i.Imaginary - j.Imaginary;

29	return result;
30	}

31	}
32	}

4.Modify the App.config file as shown

App.config

01	<?xml version="1.0" encoding="utf-8" ?>
02	<configuration>

03
04	<system.web>

05	<compilation debug="true" />
06	</system.web>

07
08	<system.serviceModel>

09	<services>
10	<service name="WcfMathServLib.MathService">

11
12	<host>

13		<baseAddresses>
14	<add baseAddress ="http://localhost:8732/Design_Time_Addresses/WcfMathServLib/MathService/" />

15	</baseAddresses>
16	</host>

17
18	<!-- Service Endpoints -->

19	<endpoint address ="" binding="wsHttpBinding" contract="WcfMathServLib.IMath">
20		<identity>

21	<dns value="localhost"/>
22	</identity>

23	</endpoint>
24

25		<!-- Metadata Endpoints -->
26	<endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>

27	</service>
28	</services>

29	<behaviors>
30

31	<serviceBehaviors>
32	<behavior>

33	<serviceMetadata httpGetEnabled="True"/>
34	<serviceDebug includeExceptionDetailInFaults="False" />

35	</behavior>
36	</serviceBehaviors>

37	</behaviors>
38

39	</system.serviceModel>
40

41	</configuration>

Result Using WCF Test Client

1. Run the WcfMathServLib project you will get the ‘WCF Test Client’
2. Select each method say ‘AddComplexNo’ Give the values in ‘Request’
3. Click on Invoke button
4. See the results in “Response”

Steps for creating ConsoleMathClient

1. Open Visual Studio 2010 and File->NewProject
2. select Visual C#->Windows in ‘Installed Templates’
3. select ‘Console Application’
4. Give Name as ConsoleMathClient
5. Click OK

2. Go to ‘Solution Explorer’ Right click on ConsoleMathClient -> Select ‘Add Service
Reference’ the below dialog will be displayed
1. Click on Discover button
2. Give namespace as ‘MathServiceReference’ and click OK

The service reference will be added now modify the program.cs as shown below.

Program.cs

01	using System;
02	using ConsoleMathClient.MathServiceReference;

03
04	namespace ConsoleMathClient

05	{
06	class Program

07	{
08	static void Main(string[] args)

09	{
10	Console.WriteLine("Press <Enter> to run the client....");

11	Console.ReadLine();
12

13	MathClient math = new MathClient();
14	Console.WriteLine("Add of 3 and 2 = {0}", math.Add(3, 2));

15	Console.WriteLine("Sub of 3 and 2 = {0}", math.Sub(3, 2));
16

17	Complex no1 = new Complex();
18	no1.Real = 3;

19	no1.Imaginary = 3;
20

21	Complex no2 = new Complex();
22	no2.Real = 2;

23	no2.Imaginary = 2;
24

25	Complex result = new Complex();
26	result = math.AddComplexNo(no1, no2);

27	Console.WriteLine("Add of 3+3i and 2+2i = {0}+{1}i", result.Real, result.Imaginary);
28

29	result = math.SubComplexNo(no1, no2);
30	Console.WriteLine("Sub of 3+3i and 2+2i = {0}+{1}i", result.Real, result.Imaginary);

31
32	Console.ReadLine();

33	}
34	}

35

}

Result

Compile and Run the project to see the Result

Another Example:

Add new project to this



Select "WCF Service Library" as shown in above figure.

Delete the two files IService1.cs and Service1.cs

Now add two classes with the names IMyClass.cs and MyClass.cs

Now your solution should look like:


Now define the service contract and operation contract in iMyclass

The sample code is as given,using System;using System.Collections.Generic;using System.Linq;using System.Text;

using System.ServiceModel;using System.Runtime.Serialization;

namespace WcfServiceLibrary1
{
        [ServiceContract]
        public interface IMyClass        {
            [OperationContract]
            string[] Answers(int a, int b);
        }
}
Implement that interface in the Myclass

The sample code is as given,using System;using System.Collections.Generic;using System.Linq;using System.Text;
 namespace WcfServiceLibrary1
{
    public class MyClass : IMyClass    {        #region IMyClass Members
 
        public string[] Answers(int a, int b)
        {
            string[] result = new string[5];
            if (a > b)
                result[0] = a.ToString() + " is greater than " + b.ToString();
            else if (a == b)
                result[0] = a.ToString() + " is Equal to " + b.ToString();
            else                result[0] = a.ToString() + " is Smaller than " + b.ToString();
 
            result[1] = "Addition is " + (a + b).ToString();
            result[2] = "Multiplication is " + (a * b).ToString();
            if (a > b)
            {
                if (b != 0)
                {
                    result[3] = "Division is " + (a / b).ToString();
                }
                else                {
                    result[3] = "Division is " + "infinite";
                }
            }
            else if (a < b)
            {
                if (a != 0)
                {
                    result[3] = "Division is " + (b / a).ToString();
                }
                else                {
                    result[3] = "Division is " + "infinite";
                }
            }
            else            {
                if (a != 0 && b != 0)
                {
                    result[3] = "Division is " + "1";
                }
                else                {
                    result[3] = "Division is " + "infinite";
                }

            }
            if (a > b)
                result[4] = "Substraction is " + (a - b).ToString();
            else if (a < b)
                result[4] = "Substraction is " + (b - a).ToString();
            else                result[4] = "Substraction is " + "0";

            return result;
        }        #endregion    }
}

Now build the solution. It is necessary that your solution will build; if it doesn't then fix the error(s) then re-build.

Now add one more project to the solution as given below:



Again delete the two files Service1.svc.cs and IService1.cs 

Add the reference of the dll which we have generated by building.

Open the service1.svc file and make the changes to make similar to the following line<%@ ServiceHost Language="C#" Debug="true" Service="WcfServiceLibrary1.MyClass"CodeBehind="MyClass.cs %>

Save it.

Now right click and select View in browser. It will show an error. No problem just take the url.

For me it gave the url : http://localhost:54640/Service1.svc

Now right click on web.config and select "Edit WCF Configuration"

Delete the Endpoints (whatever you have) then also delete the service.

Now, click on the "Create a new Service".

Click on the browse button --> Go to bin folder. You will find two Dlls over there ,

Double click both one by one so you can be given this screen,



Select That. And click on next.

Select the contract by repeating above step generally it has been given. Click next button 

Select HTTP and click next. Again next.

Now It will ask for the address give the address which we have got I am giving this addresshttp://localhost:54640/Service1.svc 

Proceed ahead and click finish.

In the end point section, Give Name Basic



Now Click on the Services it will give you following screen,

Click on link says "click to create"

Again give the name "Basic"

Now go to advanced => Service Behaviour.

Which Gives you following screen

Right click on service behavior and add new .

Click on add button,

Select ServiceMetadata.

Go to top and do like the following screen.

Just save now and exit.

Refresh the url now it will gives you something instead of error.

Actually I have forgotten one setting no problem we will do that now 

Again edit web.config by right clicking as done previously.

Try to reach following screen ,

Just enable httpgetenabled so it will look like,

Again save and exit.

Now refresh the page again it is ready to work.

Your refreshed page now look like this,

You can test the wcf from visual studio command prompt by writing

Wcftestclient http://localhost:54640/Service1.svc

Please provide your own url over here.

Now add website to our solution,

Add service reference give namespace that you want to give rest of the thing is simple as we do in the webservice.

Sample code to use this using System;using System.Configuration;using System.Data;using System.Linq;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.HtmlControls;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Xml.Linq;using ServiceReference1;

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {

        MyClassClient obj = new MyClassClient("Basic");
        string[] datas = obj.Answers(5, 10);
        foreach (string data in datas)
        {
            Response.Write(data);
        }
    }
}

Reference Books:

Download:  Programming WCF Services, 3rd Edition

Microsoft Windows Communication Foundation Step by Step

                                              Microsoft Windows Communication Foundation: Hands-on