Background <\/h3>\n
While events in WCF are nothing more than call back operations<\/strong>, however by their very nature events usually imply a looser relationship<\/strong> between the publisher and the subscriber than a typical relationship between a client and a service. The Service firing the event is called the publisher<\/strong>, and the client receiving the event is called the subscriber<\/strong>. service typically publishes the same event to multiple subscribing clients. the publisher often does not care about the order of invocation of the subscribers, or any errors, all the publishers knows is that it should deliver the event to the subscribers. <\/p>\n Since service does not care about the returned results from the subscribers. Consequently, event handling operations <\/p>\n This article has been divided into 3 modules: <\/p>\n To create this project, you can simply take a "Class Library" <\/strong>project, while choosing from project wizard option. let’s name it " so let’s define interface for the events published by the service.<\/p>\n namespace EventsLib public interface ICalcServiceEvents<\/p>\n {<\/p>\n [OperationContract(IsOneWay = true)]<\/p>\n void Calculated(int nOp, double dblNum1, double dblNum2, double dblResult);<\/p>\n [OperationContract(IsOneWay = true)]<\/p>\n void CalculationFinished();<\/font><\/p>\n } Interface simply publishes 2 method. which are basically events for the subscriber. note that, every method in this interface has been <\/p>\n First method Calculated <\/strong>is an event for the subscriber, it is fired, when calculation is done, it also passes the result to the subscribers. along with the operands and operation type.<\/p>\n Second Method CalculationFinished<\/strong> is the event, it is fired, when the Calculation is finished.<\/p>\n <\/p>\n so let’s define interface for the service.<\/p>\n namespace EventsLib [ServiceContract(CallbackContract = typeof(ICalcServiceEvents))]<\/p>\n public interface ICalcService<\/p>\n {<\/p>\n [OperationContract]<\/p>\n void Calculate(int nOp, double dblNum1, double dblNum2);<\/font><\/p>\n [OperationContract] [OperationContract] }<\/p>\n }<\/font><\/p>\n <\/p>\n Interface simple defines 3 method.<\/p>\n First Method Calculate<\/strong> is the method, that is related to business logic. that does the actual job. the other two methods are helper methods that are called by the client to subscribe a event published by the client. as you have 2 events, so you have one method for each event.<\/p>\n \/\/ Listing of CalcService.cs using System.ServiceModel;<\/font><\/p>\n namespace EventsLib public class CalcService : ICalcService<\/p>\n {<\/p>\n static Action<int, double, double, double> m_Event1 = delegate { }; <\/p>\n static Action m_Event2 = delegate { };<\/font><\/p>\n public void SubscribeCalculatedEvent() <\/strong> ICalcServiceEvents subscriber = OperationContext.Current.GetCallbackChannel<ICalcServiceEvents>();<\/p>\n m_Event1 += subscriber.Calculated;<\/p>\n }<\/strong><\/p>\n <\/strong> ICalcServiceEvents subscriber = OperationContext.Current.GetCallbackChannel<ICalcServiceEvents>();<\/p>\n m_Event2 += subscriber.CalculationFinished ;<\/p>\n } <\/strong> double dblResult = 0;<\/p>\n switch (nOp)<\/p>\n {<\/p>\n case 0: dblResult = dblX + dblY; break;<\/p>\n case 1: dblResult = dblX – dblY; break;<\/p>\n case 2: dblResult = dblX * dblY; break;<\/p>\n case 3: dblResult = (dblY == 0) ? 0 : dblX \/ dblY; break;<\/p>\n }<\/p>\n m_Event2();<\/p>\n } }<\/font><\/p>\n static Action<int, double, double, double> m_Event1 = delegate { }; Action<\/font><\/strong> keyword can be used define a delegate, can be used to pass a method as a parameter without explicitly declaring a custom delegate<\/strong>. <\/p>\n static Action <int, double, double, double> m_Event1 = delegate { }; m_Event1<\/font><\/strong> is declared as it takes four parameters. parameter list which is defined as <\/p>\n <int, double, double, double><\/font><\/p>\n that explains its parameters list and order. the encapsulated method must correspond to the method signature that is defined by this delegate. that is first parameter is an int<\/strong> and the consecutive 3 are double<\/strong>.<\/p>\n m_Event2<\/font><\/strong> is declared without any parameter<\/p>\n static Action m_Event2 = delegate { };<\/font><\/p>\n public void SubscribeCalculatedEvent()<\/p>\n you simple take take the reference of Call back channel (that is the reference of sink, that implements ICallbackServiceEvents, and assign the reference of Calculated method to m_Event1.<\/p>\n you simple take take the reference of Call back channel (that is the reference of sink, that implements ICallbackServiceEvents, and assign the reference of Calculated method to m_Event2.<\/p>\n these so this method gives a choice, whether the client want to notified about this particular event or not. <\/p>\n This function implements the business logic, simple do the desired operation as specified by nOp parameter, <\/p>\n <\/font>double dblResult = 0; {<\/p>\n case 0: dblResult = dblX + dblY; break;<\/p>\n case 1: dblResult = dblX – dblY; break;<\/p>\n case 2: dblResult = dblX * dblY; break;<\/p>\n case 3: dblResult = (dblY == 0) ? 0 : dblX \/ dblY; break;<\/p>\n }<\/p>\n <\/font> <\/p>\n after that it simply calls both the events in orderly fashion using defined delegates. <\/p>\n m_Event1(nOp, dblX, dblY, dblResult); To create this project, you can simply take a "Console Application" <\/strong>project, while choosing from project wizard option. let’s name it " before we write any code for the host, let’s define the configuration.<\/p>\n The Host application will expose the following endpoints for the service.<\/p>\n <service name="EventsLib.CalcService<\/strong>" behaviorConfiguration="CalcServiceBehavior<\/font><\/strong>"><\/p>\n <host><\/p>\n <baseAddresses><\/p>\n <add baseAddress="http:\/\/localhost:9011\/CalcService"\/> <\/host><\/p>\n <endpoint<\/strong> <\/strong>address="mex<\/strong>" binding="mexHttpBinding<\/font><\/strong>" contract="IMetadataExchange<\/font><\/strong>"\/><\/p>\n <\/service> <\/p>\n The service defines, one endpoint<\/strong> with wsDualHttpBinding<\/font><\/strong>, if you notice, you will see, that the address field has been omitted, in the end point definition. you can do this, if you define a base address for the said type. another endpoint is defined as mex<\/font><\/strong>, are defined for publication of metadata, IMetadataExchange<\/font><\/strong> is standard contract for mex<\/font><\/strong> endpoints.<\/p>\n <behaviors> <!\u2014CalcService Behavior –> <serviceMetadata httpGetEnabled<\/strong>="true"\/><\/p>\n <serviceDebug includeExceptionDetailInFaults<\/strong>="true "\/><\/p>\n <\/behavior><\/p>\n <\/serviceBehaviors><\/p>\n <\/behaviors><\/p>\n each service behavior defines two attributes, <\/p>\n Gets or sets a value that indicates whether to publich service medtadata for retrieval using an HTTP\/GET request, true means yes, metadata is available for retrieval using a HTTP\/GET request.<\/p>\n Set As we have defined the configuration for service, Let’s write code to host the service. <\/p>\n \/\/ Listing of Program.cs<\/font><\/p>\n using System; using System.ServiceModel;<\/font><\/p>\n namespace EventsLibHost class Program<\/p>\n {<\/p>\n static void Main(string[] args)<\/p>\n {<\/p>\n try<\/p>\n {<\/p>\n ServiceHost host = new ServiceHost(typeof(EventsLib.CalcService));<\/p>\n host.Open();<\/p>\n Console.WriteLine("Service is Hosted as <\/font>http:\/\/localhost:9011\/CalcService");<\/font><\/a><\/p>\n Console.WriteLine("\\nPress key to stop the service."); host.Close();<\/p>\n }<\/p>\n catch (Exception eX)<\/p>\n {<\/p>\n Console.WriteLine("There was en error while Hosting Service [" + eX.Message +"]" );<\/p>\n Console.WriteLine("\\nPress key to close.");<\/p>\n Console.ReadLine();<\/p>\n }<\/p>\n }<\/p>\n }<\/p>\n }<\/p>\n <\/font><\/p>\n Build and Execute the Host.<\/p>\n Open a command prompt in administrator mode and execute the host. here is the output. <\/p>\n\n
Using the code<\/h3>\n
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OperationContract<\/code>, and implements them, and exposes few functions to the world to use them <\/li>\nFirst Module: WCF Service Library (EventsLib.dll) <\/h3>\n
EventsLib<\/code>", it is the actual service which implements the business logic. The project already contains a file Class1.cs<\/em>, let us do some house keeping, before we write any code for the service library <\/p>\nLittle house keeping<\/h4>\n
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Defining Interface ICalcServiceEvents (ICalcServiceEvents.cs)<\/h4>\n
\/\/ Listing of ICalcServiceEvents.cs\n<\/font>using System;
using System.Text;
using System.ServiceModel;<\/font><\/pre>\n
\n
{<\/p>\n
\n
}<\/font><\/p>\nExplanation<\/h5>\n
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Defining Interface ICalcService (ICalcService.cs)<\/h4>\n
\/\/ Listing of ICalcService.cs\nusing System;
using System.Text;
using System.ServiceModel ;<\/font><\/pre>\n
\n
{<\/p>\n
\n
void SubscribeCalculatedEvent();<\/font><\/p>\n
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void SubscribeCalculationFinishedEvent();<\/p>\nExplanation<\/h5>\n
Implementing ICalcService interface (CalcService.cs)<\/h4>\n
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<\/font>using System;
\n
using System.Text;<\/p>\n
\n
{<\/p>\n
\n
{<\/p>\n
public void SubscribeCalculationFinishedEvent()
\n
{<\/p>\n
\n
<\/strong>
public void Calculate(int nOp, double dblX, double dblY)
\n
{<\/p>\n
m_Event1(nOp, dblX, dblY, dblResult);<\/p>\n
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<\/strong> }<\/p>\nExplanation<\/h5>\n
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Member variables <\/h6>\n<\/blockquote>\n
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static Action m_Event2 = delegate { };<\/font><\/p>\n<\/blockquote>\n\n
\n
<\/font><\/p>\npublic void SubscribeCalculatedEvent()<\/font><\/h6>\n
public void SubscribeCalculationFinishedEvent()<\/font><\/h6>\n
public void Calculate(int nOp, double dblX, double dblY)()<\/font><\/h6>\n
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switch (nOp)<\/p>\n
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m_Event2();<\/font><\/font><\/p>\n<\/blockquote>\nSecond Module: WCF Service Library Host (EventsLibHost.exe) <\/h3>\n
EventsLibHost<\/font><\/strong><\/code>", this application will self host the service. let us do some house keeping, before we write any code for the host application. <\/p>\nAdding application configuration<\/h4>\n
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Defining configuration<\/h4>\n
Assumption<\/h5>\n
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CalcService<\/strong><\/code> will expose HTTP endpoint at Port 9011<\/strong><\/li>\nDefining configuration for CalcService <\/h5>\n
Defining Endpoints<\/h5>\n
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<\/strong> <\/baseAddresses><\/p>\n
<endpoint<\/strong> <\/strong>address="" binding="wsDualHttpBinding<\/font><\/strong>" contract="EventsLib.ICalcService"\/><\/p>\nExplanation<\/h6>\n
wsDualHttpBinding<\/strong><\/code> provides the same support for web service protocol as WSHttpBinding<\/code>,<\/strong> but for use with duplex contracts<\/strong>. <\/p>\nDefining Behavior<\/h5>\n
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<serviceBehaviors><\/p>\n
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<behavior name="CalcServiceBehavior<\/strong><\/font>"><\/p>\nExplanation<\/h6>\n
<serviceMetadata httpGetEnabled="true" \/> <\/strong><\/font><\/pre>\n
<serviceDebug includeExceptionDetailInFaults="true "\/><\/strong><\/font><\/pre>\n
IncludeExceptionDetailsInFaults<\/code> <\/strong>to true<\/code> <\/strong>to enable clients to obtain information about internal service method exceptions; it is only recommended as a way of temporarily debugging a service application. this property must be set to false on production servers<\/strong>. <\/font><\/p>\nHosting Service<\/h4>\n
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using System.Text;<\/p>\n
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{<\/p>\n
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Console.ReadLine();<\/p>\n
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