Complete Architecture and
Development Guide To
Windows Communication
Foundation (WCF)
By Abdul khan

Author
• Abdul Khan
• IT Consultant based in Manchester, UK
• Engineering Lead, Executive, Technologist, Architect
• IT experience, within the private and public sectors (Retail, Banking, Digital, Insurance, M.O.D., HMRC, Aviation, Telecommunication,
Housing Associations, Education, Travel, and Pharmaceutical companies). Excellent architectural and strong DevOps experience with
proven-track record of delivering E2E, B2B and B2C solution on regional and global programs.
• SME in specializing in providing integration, data migration, digital transformations to the cloud solutions (Azure and AWS)
• Wealth of experience in global projects across EMEA, ASPAC and LATAM
• Liked in profile https://www.linkedin.com/in/abdul-khan-uk/

Accreditations
Thank you to my good friend and colleague for reviewing, adding value, sharing their vast experience and
knowledge.
• Steve Lampton (IT Consultant, Cloud SME) specialising in NetOps, DevOps and SecOps

Audience
Main Audience
• Technical Managers
• Architects
• Technical Leads and Developers
Assumptions
• Reader has some knowledge of development in .NET

Content
1. What Is A Service ?
2. What Is WCF?
3. WCF Architecture
4. WCF Technologies
5. WCF Features
6. Massaging Runtime Design
7. RESTful Service
8. SOAP and REST Design
9. Durable Services
10. Defining the Durable Services
11. Contracts & Service contracts
12. Data Contracts
13. Message Contracts
14. Policies and Bindings
15. Service Runtime
16. Messaging In WCF
17. Messaging Runtime/Channel Stack
18. Message Exchange Patterns
19. Message Topologies
20. Activation and Hosting
21. Understanding WCF Runtime Service Instance
23. Routing Service (WCF 4.0)
24. Discovery Service (WCF 4.0)
25. 24. Simplified configuration (WCF 4.0)
26. Metadata Exchange
27. HTTP_GET Enabled Metadata
28. Metadata Exchange Endpoint
29. Transport Security Credential Bindings
30. Types Of Authentication
31. Transfer Security Mode
32. Transport Security Mode (None)
33. Message Security Mode (Message)
34. Mixed Transfer Security Mode (Credential)
35. Security Modes (Both)
36. Throttling
37. Streaming
38. Streaming Restrictions
39. Streaming and Binding
40. Streaming and Transport
41. Transactions
42. Transaction Protocols
43. Transaction Resources
44. Transaction Client/Server transaction mode
45. Transaction None transaction mode
46. Operations
47. Request-Reply
48. One-Way
49. Callback Service
50. What Is WCF RIA Service?
51. RIA Service Architecture
52. Problem Solved By RIA
53. Domain Services
54. WCF RIA Domain Service Architecture
55. Creating WCF Service (Step-by-Step)

Complete Architecture and
Development Guide To
Windows Communication
Foundation (WCF)

1. What Is A Service?
• Service are reusable units providing business functionality that are:-
• Clearly defined using standard policies
• Clearly described
• Autonomous
• Abstraction of the underlying business logic and functionality
• Functionality exposed via structed messaging scheme
• Not XML centric, Not HTTP centric
• JOSN, XML, SOAP, Images, steaming over TCP, HTTP, Name Pipes, MSMQ etc…
• Message sent and received
• Moves from client/server model to a service model
• Rich communication patterns
• Versioning Independency
• Service Orientation provides the benefits of loosely coupled , message-oriented programming
model

2. What is WCF? (1/2)
• An API service the communicate between applications and services.
• Provides secure, reliable and transacted messaging along with interoperability
• Unifies a broad array of distributed systems capabilities in an extensible
architecture
• Spans transport, security systems , messaging patterns , encoding, networks
topologies and hosting models
• WCF combines the best off all existing Microsoft distributed computing stacks
• WCF use WS-* standards to interoperability and .NET value-add for performance
and integration with existing solutions

2. What is WCF? (2/2)
Summary, WCF provide a unified API service that’s used in various types of communication from an
application . WCF is hosted on .NET frameworks and supports distributed applications
Client Framework
Client - Consuming
Service
.NET Framework
WCF Service
WCF Service
(.NET)
MSMQ DCOM WS-*
TCP/IP HTTP/HTTPS
Messages-oriented
communication
WCF provides a unified
API for various
communication models

3. WCF Architecture
Application
Contracts
Services Runtime
Service Contract Data Contract Message Contract Policy and Binding
Throttling Behaviour Error Behaviour Metadata Behaviour Instance Behaviour
Message Inspection Transaction Behaviour Concurrency Behaviour Parameter Filtering Dispatch Behaviour
Messaging
WS-Security WS-Reliable Messaging Encoder: Binary/MTOM/XML
HTTP channel TCP Channel Transaction Flow Channel NamedPipe Channel MSMQ Channel
Activation And Hosting
Windows Activation Service .exe Windows Service COM+

4. WCF Technologies
WSE
Web Service
Enhancement
ASMX
Active Server
Methods
.NET
Remoting
Enterprise
Service
Messaging
WCF
Attribute Base
programming
Interop with Other
Platform
WS* Protocols
Support
Message Oriented
Programming
Extensibility
Location
Transparency

5. WCF Features
Address
Http://...
Binding
HTTP Transport HTTP Security
Contract
Http://...
Behaviour
Instance Behaviour
Concurrency
Behaviour
Net.p2p://..
Net.tcp://..
Net.pipe://..
Net.msmq://..
xxx://..
Peer Transport
TCP Transport
Namedpipe
Transport
MSMQ Transport
Custom Transport
WS-RM Protocol
WS-Coord Protocol
Duplex Channel
Custom Protocol
One way
Duplex
Throttling
Behaviour
Metadata
Behaviour
Error Behaviour
Custom Behaviour
Transaction
Behaviour
Security Behaviour

6. Messaging Runtime Design
Client
Services
Dispatcher
Protocol(s)
Encoder
Transport
Protocol(s)
Encoder
Transport
Binding
Address
Contract and
Behaviours

7. RESTful service
• Any Service which follows this REST architecture style is called as RESTful service. It became very
popular because of it behaviour, it is similar to the website i.e. we can load the server information
using web URL in the browser. similarly we can also access/modify the server resource using URL
in RESTful service
• RESTful service will allow the client (written in different language)to access or modify the
resource in the server using URL.
• RESTful service uses the http protocol for its communication and it is stateless
• RESTful service can transfer the data in XML,JSON,RSS,ATOM

8. SOAP and REST Design
SOAP POX(plain-old XML) REST
 Simple Object Application Protocol
 SOAP – is a package contain message
information and it will be delivered by
HTTP
 Developers are mainly preferred to user
because of its increase interoperability
 Lot of tools are available in the market to
generate the clients code from WSDL
 Plain raw XML message will be used
for communication
 Developers using POX had to write
their own code for XML and HTTP for
request/response message.
 So most of the developers moved
back to SOAP
 REST defines more of a
transport-specific model
 In reality HTTP is the only
protocol that is used in practice
today for building RESTful
architecture.

9. Durable Services
• Durable services are WCF services that persist service state information even after service host is
restarted or Client. It means that durable services have the capability to restore their own state
when they are recycled. It can use data store like SQL database for maintain instance state. It is
new feature in .NET 3.5
• You might think that we can also maintain session using WCF sessions, but content in the session
environment is not persisted by default. If the service is shut down or client closes the proxy, data
will be lost. But in case of Durable service it is still maintained.
• Working:
• When Durable service is created with database as data store, it will maintain all its state information in the
table.
• When a client make a request to the service, instance of the service is serialized, a new GUID is generated.
This serialized instance xml and key will be saved in the database. We will call this GUID as instanceID. Service
will send the instanceID to the client, so later it can use this id to get the instance state back. Even when client
is shut down, instanceId will be saved at the client side. So when ever client opening the proxy, it can get back
the previous state.

10. Defining the Durable Services
• Durable service can be implemented using [DurableService()] attribute. It takes
'CanCreateInstance' and 'CompletesInstance' property to mention on which operation instance
state has to be saved and destroyed.
• CanCreateInstance = true: Calling this operation results in creating the serialization and inserting
it into the datastore.
• CompletesInstance = true: Calling this operation results in deleting the persisted instance from
the datastore.

11. Contracts & Service contracts
• Contracts
• Contracts are the Application layers.
• 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.

12. Data Contracts
Data contracts 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.

13. Message Contract
• 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.

14. Policies and Binding
• 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.

15. Service Runtime
Service Runtime contains the behaviour's that occur during runtime of service,
they are: -
• Throttling Behaviour- Controls how many messages are processed.
• Error Behaviour - Specifies what occurs, when internal error occurs on the service.
• Metadata Behaviour - Tells how and whether metadata is available to outside world.
• Instance Behaviour - Specifies how many instance of the service has to be created while
running.
• Transaction Behaviour - Enables the rollback of transacted operations if a failure occurs.
• Dispatch Behaviour - Controls how a message is processed by the WCF Infrastructure.

16. Messaging In WCF
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 the following: -
• 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.

17. Messaging Runtime/Channel Stack
Services
Dispatcher
Protocol(s)
Encoder
Transport
Binding
Address
Contract and
Behaviours

18. Message Exchange Pattern
• One-way (Datagram)
• Message send and no response (fire and Forget, Datagram style delivery
• Request / Reply from the receiver
• Message send another message received as response (immediate reply)
• Duplex
• Sender and receiver can exchange multiple messages
• Reply later and no backchannel (call-back-style)
Sender Receiver
Sender Receiver
Sender Receiver

19. Message Topologies
• Intermediary
• Invisible to the sender, promises to not materially change the message
• A receiver message trigger a send another services
• Request / Reply from the receiver
• Message sent, one or more replies from a receiver other than the original recipient
Sender Intermediary
Sender
ReceiverSender
Receiver
Receiver

20. 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

21. Understanding WCF Runtime Service Instance
• A complete picture of WCF runtime with Service
Instance, Dispatcher and Channel Stack is as
follows:
• WCF is extensible, so we can defined our own
bindings but there are different built-in bindings
available in WCF, each designed to fulfill some
specific needs.
• basicHttpBinding
• wsHttpBinding
• netNamedPipeBinding
• netTcpBinding
• netPeerTcpBinding
Dispatcher
Channel Stack
Protocol(s)
Encoder
Transport
Service Instance
Services Method
Configuration
Binding, Protocol,
Encoding and Transport
.NET Assembly
Data Contracts, Message
Contracts, Service
Contracts

22. Routing service (WCF 4.0)
WCF 4.0 introduced routing service between client and actual business service. This
intermediated service Act as broker or gateways to the actual business services and
provides features for content based routing, protocol bridging and error handling
Service 1
Service 2
Service 3
Routing ServiceClient

23. Discovery service (WCF 4.0)
There are certain scenario in which endpoint address of the service will be keep on
changing. In that kind of scenario, client who consume this service also need to
change the endpoint address dynamically to identify the service. This can be
achieved using WS-Discovery protocol.

24. Simplified configuration (WCF 4.0)
In WCF 4.0, a simplified configuration providing default endpoint, binding and
behaviour configuration. It is not mandatory to provide endpoint while hosting
service. Service will automatically create new endpoint if it does find any endpoint
while hosting service. These changes make it possible to host configuration-free
services.

25. Metadata Exchange
• WCF provides rich infrastructure for Exporting, Publishing, retrieving and Importing the metadata.
WCF uses the Metadata to describe how to interact with the service endpoint. Using the
metadata, client will create the proxy class for the service using SvcUtil.exe
• Exporting Service Metadata
• It is the process of describing the service endpoint so that client can understand how to use the service.
• Publishing Service Metadata
• It is the process publishing metadata. It involves converting CLR type and binding information into WSDL or some
other low level representation.
• Retrieving Service Metadata
• It is the process of retrieving the metadata. It uses WS-MetadataExcahge or HTTP protocol for retrieving the
metadata. Importing Service Metadata - It is the process of generating the abstract representation of the service
using metadata.

26. HTTP_GET Enabled Metadata
• WCF use ServiceBehaviour to publish the metadata using HTTP-GET
• This can be configured either administratively or Programmatically
• Http and Https can expose by appending "?wsdl" to the end of the service
address. For example service address is http://localhost:9090/MyService , HTTP-
Get metadata address is given by http://localhost:9090/MyService?wsdl.

27. Metadata Exchange Endpoint
• Exposing the metadata using HTTP-GET has a disadvantage, such that there is no guarantee that other
platforms you interact will support it. There is other way of exposing the using special endpoint is called as
Metadata Exchange Endpoint. You can have as many metadata exchange endpoints as you want.
• Address
• It is basically Uri to identify the metadata. You can specify as address in the endpoint but append with "mex" keyword. For
example "http://localhost:9090/MyCalulatorService/mex"
• Binding
• There are four types of bindings supported for metadata exchange. They are mexHttpBinding, mexHttpsBinding,
mexNamedPipesBinding, mexTcpBinding.
• Contract
• IMetadataExchange is the contract used for MEX endpoint. WCF service host automatically provides the implementation for
this IMetadataExcahnge while hosting the service.
• You can create the Metadata Exchange Endpoint either Administrative (configuration file) or
programmatically.

28. Transport Security Credential Bindings
Name None Windows Username Certificate
BasicHttpBinding Yes(default) Yes Yes Yes
NetTcpBinding Yes Yes(default) No Yes
NetNamedPipeBinding No Yes(default) No No
WsHttpBinding Yes Yes(default) Yes Yes
WsDualHttpBinding N/A N/A N/A N/A
NetMsmqHttpBinding Yes Yes(default) No Yes

29. Types of Authentication
• WCF Authentication is basically referred to the verification of the caller who claims to the call the service.
Verification of caller will be referring as service authentication. WCF offers various authentication
mechanisms
• No authentication:- Service does not authenticate its caller and it will allow all clients to access.
• Windows authentication -Services use Kerberos when a windows domain service is available or NTLM when deployed in
workgroup configuration. In this mode caller provides the windows credential tickets/token to the service authentication.
• UserName/Password - Explicit username and password is provided to authenticate the service.
• X509 certificates - In this mode of security, client will send his certificate information to the service communication. Service
host will check and validate the caller certificate information to authenticate the service.
• Custom mechanism - WCF allows developers to replace the build-in authentication mechanism by providing user own
protocol and credential type for authentication.
• 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. E.g. windows card space

30. Transfer Security Mode
Three aspects to transfer security to consider, they are: -
• Message integrity – it ensures that message used in communication is not
tampered by any malicious party.
• Message privacy – It ensures confidentiality of the message so that no
third part can even read the message.
• Transfer security – it ensures that only authenticated user can able to read
the content of the message.

31. Transport Security Mode (None)
• When system is configured with ‘Transport’ mode, WCF uses secured communication protocol. The
available secure transports are HTTPS, TCP, IPC and MSMQ. Transport security encrypts all
communication on the channel and provides integrity, privacy and mutual authentication. It provides
point-to-point security.
• One of main disadvantage is that it can only guarantee transfer security point-to-point, meaning it
secure only at channel level. Message inside the channel will not get secured. In case of distributed
communication, multiple intermediaries between service and client will not be secure.
• It is mainly used in intranet application, binding sample :-

32. Message Security Mode (Message)
• In this mode of configuration, message will get encrypted. Encrypting the
message rather than transport enables the service to communicate securely over
non secure transport such as HTTP. It provides end-to-end security.
• One of the disadvantages of message security is that it may introduce call latency
due to its inherent overhead.
• It is mainly used in internet application.

33. Mixed Transfer Security Mode (Credential)
• It uses Transport security for message integrity, privacy and service
authentication and it uses Message security for securing client credential.
• One of disadvantage of the mixed mode is that it will secure only point-to-point
as nature of Transport security.

34. Security Modes (Both)
This mode Both transfer security mode uses both Transport security and Message
security. 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.

35. Throttling
WCF throttling provides some properties that you can use to limit how many
instances or sessions are created at the application level. Performance of the WCF
service can be improved by creating proper instance.
Attribute Description
maxConcurrentCalls
Limits the total number of calls that can currently be in progress across
all service instances. The default is 16.
maxConcurrentInstances
The number of Instance Context objects that execute at one time across
a ServiceHost. The default is Int32.MaxValue.
maxConcurrentSessions
A positive integer that limits the number of sessions a ServiceHost
object can accept. The default is 10.

36. Streaming
• Client and Service exchange message using Streaming transfer mode, receiver can
start processing the message before it is completely delivered. Streamed
transfers can improve the scalability of a service by eliminating the requirement
for large memory buffers. If you want to transfer large message, streaming is the
best method.
• The supported Steaming bindings are: -
• BasicHttpBinding
• NetTcpBinding
• NetNamedPipeBinding

37. Streaming Restrictions
• There are some restriction, when streaming is enabled in WCF, they are: -
• Digital signatures for the message body cannot be performed
• Encryption depends on digital signatures to verify that the data has been reconstructed
correctly.
• Reliable sessions must buffer sent messages on the client for redelivery if a message gets lost
in transfer and must hold messages on the service before handing them to the service
implementation to preserve message order in case messages are received out-of-sequence.
• Streaming is not available with the Message Queuing (MSMQ) transport
• Streaming is also not available when using the Peer Channel transport

38. Streaming and Binding
Only the TCP, IPC, and basic HTTP bindings support streaming. With all of these
bindings streaming is disabled by default. TransferMode property should be set
according to the desired streaming mode in the bindings.

39. Streaming and Transport
• Server transaction – Transaction setting propagated or initiated from server side
• Client transaction – Transaction setting propagated or initiated from the client side
• The main aim of the Streaming transfer mode is to transfer large size data, but default message
size is 64K. So you can increase the message size using maxReceivedMessageSize attribute in the
binding element as shown below.

40. Transaction
• A transaction is a collection or group of one or more units of operation executed as a whole. It
provides way to logically group single piece of work and execute them as a single unit. In addition,
WCF allows client applications to create transactions and to propagate transactions across service
boundaries.
Recovery Challenge
• The challenge we will phased and how to recover from it, therefore we need to consider the
following : -
• Consider a system maintained in consistent state, when application fail to perform particular operation, you
should recover from it and place the system in the consistent state.
• While doing singe operation, there will be multiple atomic sub operation will happen. These operations might
success or fail. We are not considering about sub operation which are failed. We mainly consider about the
success operation. Because we have to recover all these state to its previous consistence state.
• Productivity penalty has to be payee for all effort required for handcrafting the recovery logic
• Performance will be decreased because you need to execute huge amount of code.

41. Transaction Protocols (1/2)
Best way to maintain system consistence and handling error-recovery challenge is
to use transactions. Below figure gives idea about transaction.
 Committed transaction: Transaction that execute successfully and transfer the system from consistence state A to B.
 Aborted transaction: Transaction encounters an error and rollback to Consistence State A from intermediate state.
 In-doubt transaction: Transactions fail to either in commit or abort.
Consistent
State
B
Committed Transaction
Temporary Consistence State
Abort Transaction
Consistent
State
A

41. Transaction Protocols (2/2)
As a developer we no need to concern about transaction protocols and transaction manager used
by WCF. WCF itself will take care of what kind of transaction protocols should be used for different
situation. Basically there are three different kinds of transaction protocols used by WCF.
Attribute Description
Lightweight
• This protocol are used to manage the transaction with in same application
domain
• Best performance compare to other
OleTx
• This protocol are used to manage the transaction in an internet and in a
windows environment
WS-Atomic
Transaction (WAST)
• It can propagate transaction across firewalls.
• Primary used in Internet with multiple transactions manager are involved

42. Transaction Propagation
Transaction Flow Option Binding configuration Description
NotAllowed
transactionFlow="true"
or
transactionFlow="false"
Client cannot propagate its transaction to service even client has
transaction
Allowed transactionFlow="true"
Service will allow to flow client transaction.
It is not necessary that service to use client transaction.
Allowed transactionFlow="false"
If service disallows at binding level, client also should disable at binding
level else error will be occurred.
Mandatory transactionFlow="true" Both Service and client must use transaction aware binding
Mandatory transactionFlow="false"
InvalidOperationException will be throw when service binding disables
at binding level.
Fault Exception will be thrown when client disable at its binding level.
In WCF, transaction can be propagated across service boundary. This enables service to participate in a client transaction and
it includes multiple services in same transaction, Client itself will act as service or client.
We can specify whether or not client transaction is propagated to service by changing Binding and operational contract
configuration

43. Transaction Resources
• Transactional programming requires working with a resource that is capable of participating in a transaction,
and being able to commit or roll back the changes made during the transaction. Such resources have been
around in one form or another for decades. Traditionally, you had to inform a resource that you would like to
perform transactional work against it. This act is called enlisting. Some resources support auto-enlisting.
• Transaction Properties
• Transaction can be said as pure and successful only if meets four characteristics.
• Atomic - When transaction completes, all the individual changes made to the resource while process must be made
as to they were all one atomic, indivisible operation.
• Consistent - transaction must leave the system in consistent state.
• Isolated - Resources participating in the transaction should be locked and it should not be access by other third party.
• Durable - Durable transactions must survive failures.

44. Transaction Client/Server transaction mode
• This settings ensures the service uses only the client’s transaction, Enable the TransactionFlow=true in binding
configuration
• Set TransactionFlowOption.Mandatory in the operation contract
• Set TransactionScopeRequired=true in the operation contract
• This setting ensures that service uses the client’s transaction if possible or a server side transaction when the client
does not have a transaction.
• Enable the TransactionFlow=true in binding configuration
• Set TransactionFlowOption.Allowed in the operation contract
• Set TransactionScopeRequired=true in the operation contract
This ensures that the service always has a transaction, separated from any transaction its client may or may not have.
• Disable the TransactionFlow=false in binding configuration
• Set TransactionFlowOption.NotAllowed in the operation contract
• Set TransactionScopeRequired=true in the operation contract

45. Transaction None transaction mode
This setting ensures service does not use transaction
• Disable the TransactionFlow=false in binding configuration
• Set TransactionFlowOption.NotAllowed in the operation contract
• Set TransactionScopeRequired=false in the operation contract

46. 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 call-back(service to call back the client)
• Three modes of communication between client and service are
• Request- Replay
• One-Way
• Call-back

47. Request-Reply
• By default all WCF will operated in the Request-Replay mode. 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 start executing the rest of the statement. If service doesn't
respond to the service within receiveTimeout, client will receive TimeOutException.
• Apart from NetPeerTcpBinding and the NetMsmqBinding all other bindings will support request-
reply operations.
Client
Service
Request
Response
Wait State

48. 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
Service
Request
Continue
Processing the
next
statement

49 .Callback Service
• WCF provides the service to call the client. In which, service will act as client and client will act as service. HTTP protocols
are connectionless nature, so it is not supported for callback operation. So BasicHttpBinding and WSHttpBinding cannot be
used for this operation.
• WCF support WSDualHttpBinding for call back operation.
• All TCP and IPC protocols support Duplex communication. So all these binding will be used for callback operation.
Client Service
Request
Response
Duplex Proxy
OnCallback() Callback instance call OnCallback()
Operational Context
Callback instance
Instance Context
Callback instance

50. What Is WCF RIA Service?
• WCF RIA service is a framework to develop n-tier application for Rich Internet Application (RIA). It
is mainly used in RIA applications like Silverlight, AJAX client, etc. It solves the major problem
while developing business application like decoupling the resource access, application logic and
presentation layer. WCF RIA service was introduced in Silverlight 4 with .NET framework 4, and it
can be developed using visual studio 2010.
• WCF RIA service will generate the code at the client side related to the service and domain
entities declared at the server side.
• RIA service exposes the data from server side to client side using Domain service, RIA service
framework implements the each domain service as WCF service to access the data as business
entity.

51. RIA Service Architecture
Client Service
Single Application Logic
WCF
Services
WCF
UI
(Views)
Application
Logic
Application
Logic
Data Access
Logic
DB

52. Problem Solved By RIA
• To have best performance of the RIA application, app logic need to be available in client and server
side. This problem is solved by auto generating the code at the client side while recompiling the
project.
• Asynchronous call – Async service call are supported in Domain service by using WCF infrastructure
• Handling large data and data across different tier – Large amount of data can be access and filter using
IQueryable object. Since entity objects used in domain service are serializable and so it can be access
across different layer
• Security/Access control – ASP.Net membership frameworks are integrated with RIA service to provide
security systems to RIA service
• Validation – Entity can be validated based using adding attribute to the class members

53. Domain Services
• Domain services are WCF services that expose the business logic of a WCF RIA Services application. Domain
service contains set of business related data operation and it is exposed as WCF service.
• The Domain Service class is the base class for all classes that serve as domain services.
• DomainServiceHost is the hosting class for domain service; internally
• DomainServiceHost uses the WCF ServiceHost class to host the application.
• A domain service class must be marked with the EnableClientAccessAttribute attribute to make the service
available to the client project. The EnableClientAccessAttributeattribute is automatically applied to a domain
service when you select the Enable client access check box in the Add New Domain Service Class dialog box.
When the EnableClientAccessAttribute attribute is applied to a domain service, RIA Services generates the
corresponding classes for the client project.

54. WCF RIA Domain Service Architecture
Server Stack
Domain
Service
Domain
Service Host
Client Stack
Domain
Service
Domain
Service Host
RIAService
WCF Service
WCF Client
Channel
WCF Service
Contract
WCF Service
Contract
Client

55. Creating WCF Service (Step-by-Step)
Step-by-step guide in creating a WCF Service
Define .NET service interfaces to serve as the Service Contract
Implement Service Contract in .NET class as Service type and configure its behaviour
Configure the End Point where service will expose, by specifying A,B,C
Host Service type in application using WCF hosting infrastructure
At Client side, by using description of target End Point create PROXY and write the code against the proxy type.
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By Abdul Khan – https://www.linkedin.com/in/abdul-khan-uk/