WCF TUTORIAL FOR BEGINNERS PDF
This tutorial explains the fundamentals of WCF and is conveniently divided The objective of this tutorial is to help those readers who want to learn the basics of. WCF: Application Structure and Code Examples. Creating a client to consume the hosted Service. application containing three basic components: 1. 12 Implementing a WCF Service for Good Performance. Visual Studio actually provides two templates for creating a WCF service; the WCF http:// resourceone.info
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See the WCF Developer Center, especially Getting Started with Windows A Beginner's Tutorial for Understanding Windows Communication. As Figure 2 shows, WCF allows creating clients that access services. Both the . To allow more than just basic communication, WCF implements Web services. WCF for Beginners and Experiaced with resourceone.info - Ebook download as PDF Transactions WCF Fundamental In this part of tutorial you are going to learn.
Testing the Fault contract". Instance mode can be configured using ServiceBehavior attribute. This Service instance will be disposed after response is sent back to client. Single ] public class MyService: This can be specified at implementing the service contract as shown below. Service instance will be created for each client request. Let as understand the per-call instance mode using example. Add service behavior attribute to the service class and set the InstanceContextMode property to PerCall as show below.
Create the service contract called IMyService and implement the interface. Following diagram represent the process of handling the request from client using Per-Call instance mode. WriteLine "Client making call to service. WriteLine "Service Instance mode: Each time while making call to the service.
Service instance will created for each request and value of static variable will be set to one. Client side. While return back. Output is shown below. PerCall ] public class MyService: In this implementation of MyMethod operation. When the client creates new proxy to particular service instance.
Following diagram represent the process of handling the request from client using Per-Session instance mode. Add service behavior attribute to the service class and set the InstanceContextMode property to PerSession as show below.
Let as understand the Per-Session instance mode using example. It is independent of all other instance.
So each time request is made to the service. Service instance will be created once the proxy is created at client side. So each call to MyMethod return incremented value. PerSession ] public class MyService: Following diagram represent the process of handling the request from client using Singleton instance mode. This singleton instance will be created when service is hosted and. Let as understand the Singleton Instance mode using example.
Add service behavior attribute to the service class and set the InstanceContextMode property to Single as show below. WriteLine "Client 1 making call to service. Service instance is created when it is hosted. WriteLine "Client 2 making call to service.
So this instance will remain till host is shutdown. Basically service instance is hosted in a context. BeforeCall] public int Add int num1. Session actually correlated the client message not to the instance. When session starts. WCF provides the option of separating the two lifetimes and deactivating the instance separately from its context.
ReleaseInstanceMode property of the OberationalBehavior attribute used to control the instance in relation to the method call. BeforeCall 3. None 2. AfterCall 4. BeforeAndAfterCall Below code show. Followings are the list Release mode available in the ReleaseInstanceMode 1. This is designed to optimize a method such a Cleanup ReleaseInstanceMode. By default ReleaseInstanceMode property is set to 'None'. None This property means that it will not affect the instance lifetime.
AfterCall This property means that it will deactivate the instance after call is made to the method. BeforeCall This property means that it will create new instance before a call is made to the operation. WCF deactivates the instance and calls Dispose before the call is done. If the instance is already exist. This is designed to optimize a method such as Create ReleaseInstanceMode. It can use data store like SQL database for maintain instance state.
BeforeCall and ReleaseInstanceMode. Net 3. AfterCall Explicit Deactivate You can also explicitly deactivate instance using InstanceContext object as shown below. This has combined effect of using ReleaseInstanceMode. It means that durable services have the capability to restore their own state when they are recycled.
This is means that it will create new instance of object before a call and deactivates the instance after call. It is new feature in. Service will send the instanceID to the client. It takes 'CanCreateInstance' and 'CompletesInstance' property to mention on which operation instance state has to be saved and destroyed. Calling this operation results in creating the serialization and inserting it into the datastore. If the service is shut down or client closes the proxy.
Calling this operation results in deleting the persisted instance from the datastore. Even when client is shut down. So when ever client opening the proxy. This serialized instance xml and key will be saved in the database. But in case of Durable service it is still maintained. When Durable service is created with database as data store. You might think that we can also maintain session using WCF sessions.
When a client make a request to the service. Create interface and decorate with Service and Operation contract. Let us understand more about the durable service by creating Simple Calculator service which persist the instance state in SQL server database. You need to add [Serializable] And [DurableService ] attribute to the service implementation. Select the 'WCF Service' as shown below. Before configuring the database information in the durable service.
In this implementation. Microsoft provides inbuilt sqlPersistance provider. In order to support durable service. To set up the database environment. Create the console client application and name it as DurableServiceClient Step 7: Retrieve and set the context at the client side.
Create the Helper class called it as Helper. This helper class is used to Store. Copy and paste the below code to your helper file. SetContext ctx. Serialize fs. Delete TokenContextFileName. When I call the Subtract and Multiply operation. SaveContext client. Add SetContext client. In the main method.
Call to this method will add instance state to the database. Subtract 2. Multiply 5. Now I have closed the proxy and creating new proxy instance. I was creating the proxy for the service and calling the Add operation.
Output of the client application. Serialized XML instance state save in the database is shown below. Attribute maxConcurrentCalls Description Limits the total number of calls that can currently be in progress across all service instances. Performance of the WCF service can be improved by creating proper instance. The default is Throttling WCF throttling provides some properties that you can use to limit how many instances or sessions are created at the application level.
A positive integer that limits the number of sessions a ServiceHost object can accept. Open ; Operations In classic object or component- oriented programming model offered only single way for client to call a method. Client will issue a call, block while the call was in progress, and continue executing once the method returned.
WCF will support classical Request-Replay model, along with that it also supports One-Way call call and forget operation and callback service to call back the client Three modes of communication between client and service are 1. It means that, when client make a request to the WCF service and client will wait to get response from service till receiveTimeout.
After getting the response it will.
If service doesn't respond to the service within receiveTimeout, client will receive TimeOutException. One-Way In One-Way operation mode, client will send a request to the server and does not care whether it is success or failure of service execution. There is no return from the server side, it is one-way communication. Client will be blocked only for a moment till it dispatches its call to service. If any exception thrown by service will not reach the server.
Client can continue to execute its statement, after making one-way call to server. There is no need to wait, till server execute. Sometime when one-way calls reach the service, they may not be dispatched all at once but may instead be queued up on the service side to be dispatched one at a time, according to the service's configured concurrency mode behavior.
If the number of queued messages has exceeded the queue's capacity, the client will be blocked even if it's issued a one-way call. However, once the call is queued, the client will be unblocked and can continue executing, while the service processes the operation in the background.
One-way operation can be enabled by setting IsOneWay property to true in Operation contract attribute.
Client will be blocked until operation completes. Suppose If you want to make use of One-way operation in Sessionful service. It will be good practice. This operation should not return any value. In the below example you can find the decalration of the callback contract and it is configured in the ServiceContract attribute.
In which. Defining and configuring a callback contract Callback service can be enabled by using CallbackContract property in the ServiceContract attribute. Callback Service Till now we have seen that the all clients will call the service to get the things done. In the presence of transport session. Client will not be able to make new call using same proxy instance. So all these binding will be used for callback operation. But WCF also provides the service to call the client.
The client must use a proxy that will set up the bidirectional communication and pass the callback endpoint reference to the service. In the earlier part of the tutorial I have mention that InstanceContext is the execution scope of inner most service instance.
It provides a constructor that takes the service instance to the host. So client has to expose a callback endpoint to the service to call. Add System. ServiceModel reference to the project Step 3: Create the Callback and Service contract as shown below. Implementation of the Callback contract will be done on the client side.
You need to mention CallbackContract property in theServiceContract attribute. The following code shows the callback method invocation. Service can call the client side callback method using reference e to the client side callback instance. Using that instance we are calling the OnCallback method from client side.
Implement the Service contract as shown below. In the below code you will find using OperationContext is used to receive the reference to Callback instance. Multiple ] public class MyService: If you are calling the Callback method inside the service method. This is because when a client made a call to the service. This application is used to self-host the WCF service.
Service will try to access the lock channel. So you can set ConcurrencyMode to Multiple or Reentent so it will release the lock silently. If you are not using ConcurrencyMode to Multiple or Reentent. Use Duplex binding to support Callback operation. Press key to stop the service. This is the client application which contain Callback implementation.
Run the host application Step 9: Create the contractor which will accept InstanceContext as parameter. ServiceModel and CallbackService as reference to the project Step Create the proxy class as shown below. Use DuplexClientBase to create the proxy. An event may result from a direct client call. The service firing the event is called the publisher. WriteLine "Callback method is called from client side. In the output.
Create the implementation for Callback Contract class MyCallback: Run the client application. Publisher will be blocked. It will not affect the client. Subscriber can be executed in any manner. Net delegates to manage the list of subscribers. These make publishers to put in wait state. Let us consider the scenario in which you what to publish large volume of event. It may lead Publisher event not to reach other subscriber. Since service has to communicate to the client.
Here we are using one operation to subscribe the event and another for firing the event. PerCall ] public class MyPublisher: DoSomethingAndFireEvent operation will fire the event as shown. I am using Operationcontext to get the reference to the client instance and Subscription method is added as event handler to the service event.
Implementation of the Service Contract is shown below. This application will be used to self-host the service. In the Subscription operation. ServiceModel and WcfEventService as reference to the project. WriteLine "Host is running.. This application will act a client which is used to subscribe the event from service. Run the host application as shown below. Create the console application using visual studio and name it as WcfEventServiceClient as shown below.
Implementation of IMyEvents at client side is shown below. This method will be called when service publish the event. This is true whether it is the client sending a message to the service or the service returning a message to the client. Transfer mode In our normal day today life. If data transfer is taking place through WCF service. WriteLine "Client call operation which will fire the event".
Streamed transfers can improve the scalability of a service by eliminating the requirement for large memory buffers. StreamRequest In this mode of configuration. Subscriber got notification. As a result. Based on the size and other condition of the data transfer. WCF supports two modes for transferring messages Buffer transfer When the client and the service exchange messages. If you want to transfer large message.
Run the client application and you see the when event is fired from the service. Stream transfer When client and Service exchange message using Streaming transfer mode. In this mode of configuration. NetworkStream are derived from it. Streaming Client and Service exchange message using Streaming transfer mode. Net stream class for Streaming the message. Stream and it's subclass can be used for streaming. Stream the data. Stream in base class for streaming. Send and accept requests in streaming mode.
TransferMode property should be set according to the desired streaming mode in the bindings. Stream and MemoryStream are serializable and it will support streaming 3. FileStream is non serializable. So you can increase the message size using maxReceivedMessageSize attribute in the binding element as shown below.
Send and accept requests in buffered mode. With all of these bindings streaming is disabled by default. Transaction Resources Transactional programming requires working with a resource that is capable of participating in a transaction. While doing singe operation. Below figure gives idea about transaction. Productivity penalty has to be payee for all effort required for handcrafting the recovery logic 4.
In addition. Solution Best way to maintain system consistence and handling error-recovery challenge is to use transactions. Recovery Challenge Let us discuss more on challenge we will phased and how to recover from it. Such resources have been around in one form or another for decades. Transaction encounters an error and rollback to Consistence State A from intermediate state.
These operations might success or fail. Transaction that execute successfully and transfer the system from consistence state A to B. Transactions fail to either in commit or abort. Consider a system maintained in consistent state.
It provides way to logically group single piece of work and execute them as a single unit. WCF allows client applications to create transactions and to propagate transactions across service boundaries. We are not considering about sub operation which are failed. Some resources support auto-enlisting. We mainly consider about the success operation.
Windows Communication Foundation
Performance will be decreased because you need to execute huge amount of code. This act is called enlisting. Because we have to recover all these state to its previous consistence state. When transaction completes. Transaction Properties Transaction can be said as pure and successful only if meets four characteristics.
Durable transactions must survive failures. In which service starts and manage the transaction. Resources participating in the transaction should be locked and it should not be access by other third party. Any network failure or machine crash also increases the complexity for managing the transaction. Now the questions arise that which service will begin the transaction?
Which service will take responsibility of committing the transaction? How would one service know what the rest of the service feels about the transaction? Service could also be deployed in different machine and site.
WCF come up with distributed transaction using two way committed protocol and dedicated transaction manager. Client itself will act as service or client. If service disallows at binding level. This enables service to participate in a client transaction and it includes multiple services in same transaction. TransactionFlow can be enabled only at the operation level not at the service level. FaultException will be thrown when client disable at its binding. Transaction Mode This article explains about the how to configure the service and client transaction mode in WCF service.
Allowed in the operation contract 3. Transaction Protocols As a developer we no need to concern about transaction protocols and transaction manager used by WCF. Set TransactionFlowOption. Basically there are three different kinds of transaction protocols used by WCF.
WCF itself will take care of what kind of transaction protocols should be used for different situation. NotAllowed in the operation contract 3. This seeing ensures that the service always has a transaction. This setting ensures service does not use transaction 1.
Mandatory in the operation contract 3. Allowed ] bool AddEmployee int id. This attribute is used to enable the service transaction when the client transaction is not available. Modify the service application to throw exception explicitly after successfully insert statement execution and check the transaction behavior.
Create the Employee WCF service to allow client user to insert employee detail 2. TransactionFlowOption take three set of values. Run the client application to successfully insert the employee detail 5. WCF transaction was explained with below employee service 1. Create the Employee service that allows the addition of new employee details in DB.
Create the client application by consuming the Employee Service and insert the employee details 4. Decorate the operation contract with TransactionFlow attribute for enabling the transaction. Enable the transaction from server side by setting proper attributes 3. Update the service endpoint to enable transactions for wsHttpBinding by setting the transactionFlow attribute to true.
It is required to set the transaction at the service contract level as mention in Step 1. Create a new console application from add Employee service as ServiceReference Step 5: Create a new proxy object for the employee service and call the AddEmployee method.
AddEmployee 1. WriteLine "Error while adding employee details". Output shows the employee detail is added successfully and DB also shows the new entry is made Step 6: Now everything works fine.
WriteLine "Employee details add successfully". WriteLine ex. Run the client application and check the output. WCF RIA service will generate the code at the client side related to the service and domain entities declared at the server side.
DB is not updated. It solves the major problem while developing business application like decoupling the resource access. RIA service client will be updated with business rule and entity present at the server side. Result clearly says that even insert statement is executed successfully and error is thrown after insert statement. Main problem developer are facing while developing the n-tier RIA application will be coordinating the application logic between middle tier and presentation tier.
It is mainly used in RIA applications like Silverlight. Because all the code execution is comes under the transaction so failure in any module of code will revert back all code execution. WCF RIA service will allow developer to write the set of service code and this server code will be available to the client side without manually duplicate that programming logic.
AJAX client. A domain service class must be marked with the EnableClientAccessAttribute attribute to make the service available to the client project.
RIA Services generates the corresponding classes for the client project. RIA service exposes the data from server side to client side using Domain service. Domain service contains set of business related data operation and it is exposed as WCF service.
When the EnableClientAccessAttribute attribute is applied to a domain service. RIA service framework implements the each domain service as WCF service to access the data as business entity. Problems solved in RIA Service 3. Since entity objects used in domain service are serializable and so it can be access across different layer 4. To have best performance of the RIA application. Client" fig: Asynchronous call — Asynch service call are supported in Domain service by using WCF infrastructure 3.
This problem is solved by auto generating the code at the client side while recompiling the project. Handling large data and data across different tier — Large amount of data can be access and filter using IQueryable object.
DomainContext class available inside the name space "System. Validation — Entity can be validated based using adding attribute to the class members Example: This is the data class which will return list of Employee and update the employee list Data Model class: Add code to return the Employee list Domain Service class: Create methods containing your application logic. Create domain service class. By right click project file and select Add new item. To expose the Employee related operation to the client side.
Compile the solution — After compilation RIA service will generate the application logic at the client side using DomainContext object. Domain Context class at client: Update emp. Enable show all files option for the solution and view the auto generated code.
View the DomainContext class are created at the client side. DataGrid x: Add DataGrid to Main.
Run the application and see the output as shown below. It became very popular because of it behavior. Other operations like POST. Download Souce: This Restful service will be consumed using client console application. Data Model class: This sample explains about the creating the RESTful service to create and updating the resource information available at the sever side. Remove existing. Interface and Implementation: Employee GetEmployee int Id. OperationContract and DataContract as shown below.
IEmployeeService As it is mention in introduction section of RESTful service. Add newEmp. Method exposed at the server side can be call using url.
This service can be hosted as normal WCF service by creating the ServiceHost object and adding endpoint with different binding. Update newEmp. Allowed ] Delete System. ToInt32 empId. Just type the url in the web browser to read all the employee details. Endpoints Console. By hosting the restful service with WebServiceHost host class will automatically set the binding and other configuration setting.. We can access the RESTful service using browser.
WriteLine "ASP. In the below code you can see that I have only mention url for the hosting. In the above interface declaration. For this example we are using console application for hosting service. Now we have completed with service implementation project.
Below code first read the employee details from the server and add new employee and once again it read the employee details to confirm the added resource. Now we can start with client application. If we need to get specific employee details.
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Below sample is the ASP. Date Verification of caller will be referring as service authentication. This will make sure that communication channel between client and service is secured. Types Of Authentication 2. Transfer Security Mode 3. Transport Security Protection Level 4. Message Security Level Types of Authentication WCF Authentication is basically referred to the verification of the caller who claims to the call the service.
WCF offers various authentication mechanisms. When WCF service is created. X certificates: In this mode of security. Message integrity — it ensures that message used in communication is not tampered by any malicious party. Service host will check and validate the caller certificate information to authenticate the service. Transfer security — it ensures that only authenticated user can able to read the content of the message.
Windows authentication: Services use Kerberos when a windows domain service is available or NTLM when deployed in workgroup configuration. No transfer security mode: This ensure that no security is applied while communication between server and client. No authentication: Service does not authenticate its caller and it will allow all clients to access. WCF supports five different modes of transfer security to accomplish above three aspects. Message privacy — It ensures confidentiality of the msessage so that no third part can even read the message.
Issue token: The caller and the service can both rely on a secure token service to issue the client a token that service identify and trust. Custom mechanism: WCF allows developers to replace the build-in authentication mechanism by providing user own protocol and credential type for authentication. Explicit username and password is provided to authenticate the service. One of main disadvantage is that it can only guarantee transfer security point-to-point. Encrypting the message rather than transport enables the service to communicate securely over non secure transport such as HTTP.
It provides point-to-point security. One of disadvantage of the mixed mode is that it will secure only point-to-point as nature of Transport security. Transport security encrypts all communication on the channel and provides integrity.
One of the disadvantages of message security is that it may introduce call latency due to its inherent overhead. Message inside the channel will not get secured. It uses Transport security for message integrity. It provides end-to-end security. It is mainly used in internet application. WCF uses secured communication protocol. In case of distributed communication.
So message is secured using Message security and then it is transferred to the service using secure transport. This mode will maximize the security but overload the performance. This mode Both transfer security mode uses both Transport security and Message security. When configure transfer security for Transport security. Format "You entered: It makes sure that Windows authentication is used else it will throw exception.
This indicate the service should not auto-impersonate 2. In this case. Impersonate all operation: Impersonation can be allowed for all operation by setting the service Authorization in service behavior section as shown below. Make sure it is commented. Create client application and create the proxy for the WCF service Step 4: Make sure that client side configuration are updated with "Windows" Authentication as mention below Step 5: Sample client code to consume the service Note: If Metadata Exchange Endpoint is enabled in service configuration.
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Make sure both are using same config settings. What's new in WCF 4. Microsoft has brought new feautes in WCF 4. In old version of WCF, configuration files are not validated while building the project. But in WCF 4. In WCF4. This is done for both synchronous and asynchronous method.
This allows the client application to call the service operation using Task based programming model. In WCF 4. Old form of async operations methods are created in the proxy class. In old version WCF, configuration files generated at the client side will have all default setting and it looks complex.
Part 3 Default. NET Compatibility Mode. If you create the proxy using "SvcUtil. Configuration file generated in WCF 4. Contract file creation using SvcUtil.
WCF for Beginners and Experiaced with Examples.pdf
Using "SvcUtil. WCF 4. Net Compatibility Mode: In this mode. In this mode does not participate in ASP.
Net HTTP pipeline and it is similar to old web service. NET features such as File Authorization. This would cause large memory consumption.
When WCF service is sending streamed messages to multiple clients. XmlDictionaryReaderQuotas XmlDictionaryReaderQuotas contains configurable quota values for XML dictionary readers which limit the amount of memory utilized by an encoder while creating a message. Service will be block its thread to transfer to next client till the slow client is received the message. While these quotas are configurable. NET 4. So when third party try to consume the service using WSDL has to explicitly add these references.
WebSocket is designed to be implemented in web browsers and web servers. Two new bindings are added in WCF4. Part 5. It is so simple WCF 4.
Browse the wsdl file from IIS. This method will be called before service host is opened. Code sample: In older version of WCF 4. If static Configuration method is specified. Part 6. Add new MyEndpointBehavior. AddServiceEndpoint se. But in case of WCF 4. WCF provides option to configure the service using config file or through code. Type of compression can be mention in the binding settings Points to remember: WCF binary message encoder supports message compression.
You need to create the custom binding to use this feature 4. Creating ChannelFactor will increase the overhead by following operation. In the case where the CPU is the bottleneck.
WCF for Beginners and Experiaced with Examples.pdf
Compression will work for HTTP. Compression is mostly useful if network bandwidth is a bottleneck. Disposing of resources In order to avoid this overhead. Both the client and the service must configure the CompressionFormat property. Constructing the channel stack 4. Constructing the ContractDescription tree 2. Reflecting all of the required CLR types 3. Net application. In old version WCF. But in case of WCF4.
GetEmployeeDetails id. Set the authentication as mention below. Now WCF 4. Client can call the service by using IDN name Fig 1: Display the config settings. Introduction to OData OData. DnsSafeHost is converted to Punycode for internet addresses. Below diagram explains about the different types of Data sources and it connection to different types of Clients using OData.
Host remains Unicode and uri. Business Intelligence. SQL Database. In real time scenario. Open Data Protocol is method to access the information exposed by different data source Cloud storage.
Host or Uri. But it is always good to have single point of contact and mode to access the different sources. Custom application.. You will need to be an experienced developer who has a fair understanding of. NET and C 2. A couple of points about Programming WCF Services, first, this isn't a beginners book; the author dives down into advanced material in spots almost without notice.
If you want to become proficient using WCF, you will be buying this book eventually. You will find that this book will become both a reference as well as well as a guide. This book is very good for beginners. This books covers all the topics in WCF in general. I will recommend this book, for initial stage of learning. Covering the concepts and details necessary to enable you to build connected solutions, this book offers hands-on guidance for creating the Web services you need to implement robust business applications for Windows.
Teach yourself the essentials of Windows Communication Foundation-one step at a time. With this practical tutorial, you get hands-on guidance for creating the Web services you need to implement robust business applications for Windows.Publisher will be blocked. Serialization, whereas a web service supports XML serializer by making use of System.
Press key to stop the service. When Durable service is created with database as data store. WebSocket is designed to be implemented in web browsers and web servers. Service will send the instanceID to the client. Each Endpoint is a portal for communicating with the world. Let as understand the per-call instance mode using example.
WCF deactivates the instance and calls Dispose before the call is done. By default namespace is the same as the namespace of the service contract that the message is participating.
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