Windows Communication Foundation

1. Windows Communication
Foundation
Vijay Krishna Parasi

2. AGENDA
• Why WCF Service & SOA Architecture
• ABC’s of WCF
• Hosting
• MEX Endpoint
• Contracts
– WSDL
– SOAP

3. SOA Architecture Example

4. ABC’s
Letter
Where How What PostBox
(Address) (Binding) (Contract)
End
Point

5. Address : “the Where”
– Where the network messages should be sent.
HTTP:
http://myserver/myservice
TCP:
net.tcp://myserver:8080/myservice

6. Binding : “the How”
– How the messages should sent.
– Defines the channel used to communicate with an
endpoint.
– Channels will have series of binding elements.
– The lowest level of binding element is Transport.
– The built in transport protocols are HTTP, TCP, Named
Pipes etc…

7. Contract : “the What”
– Defines capability of endpoint.
– Defines the operations that endpoint exposes.
– Also defines the message formats that the operations
require.
– They maps to the class methods that endpoints.

8. WCF Service
End Point
Messages
WCF Client End Point
End Point
Service:
Can have more than one end points.
Listens for messages on the address specified by the endpoint(s).
Expects the messages to arrive in specified format.

9. Hosting
– To make service up and running.
– And to make service respond to the client requests.
– Hosting can be anything Console App, Web Application,
IIS etc...
– Hosting in IIS requires svc file.

10. Metadata Exchange (MEX) Endpoint
– For Service Discoverability.
– Helps the clients to obtain the information of ABC’s in the form of
WSDL (Web Service Description Language).
– When user clicks on Add Service Reference or use svcutil.exe, MEX
endpoint will be called.
– Client gets WSDL  Below artifacts will be generated
• Proxy class in the language of the project.
• Application configuration file
– To configure MEX Endpoint,
• Enable the “HTTP Get” behavior. Allows the user to access MEX endpoint via
browser.
• Add a MEX endpoint including the other endpoints.

11. WCF Service
End Point
Messages
WCF Client End Point
End Point
MEX End Point
MEX Endpoint:
Must for a service to expose ABC’s to client.

12. Calling WCF Service from Client
– Can be called in two ways
• Channels - Using Custom Code
• Svcutil.exe Using Tools
– Channels:
• Interface definition is shared b/w the client & service.
• Client creates a ChannelFactory class to create a channel
using ABC’s.
• Using the channel object client calls the service methods.
– Svcutil.exe
• Add Service Reference from Visual Studio.
• Internally calls the svcutil.exe

13. DEMO
– Implementing a WCF service includes.
• Implement a .NET class
• Decorate the class with System.ServiceModel attributes.
– System.ServiceModel namespace will be installed
with.NET 3.0
– WCF Service can be implemented,
• Writing entirely in Code
• Writing in Code & Configuration files
If we specify an address in the endpoint it overrides the
base address.

14. – ServiceContract
• Marks a class as Contract.
• Expressed in standards based on WSDL.
– OperationContract
• Defines methods that can be invoked on the class.
• Defines the messages that are passed to and from service
methods.
• Operations & Messages
– Within the Endpoint definition we will specify the
Address, Binding & Contract.

15. – When service is started by host
• WCF starts the listener listens incoming requests on the
configured address.
• In case of IIS hosting, the listener is likely already started, WCF
registers its listener with IIS.
– When a message arrives, the service host
• First, based on the channel stack defined by binding it applies
decompression, decryption and security rules.
• Second, based on the contract it deserializes the incoming
message into .NET types and invokes the proper operation.

16. Once again ABC’s
– Each endpoint constitute ABC’s
• An addressable location on the network where messages are sent.
• A binding that describes how messages are sent.
• A contract that describes the message formats.

17. Let’s understand “Contracts”
– Contract is binding agreement
• B/w parties that specifies the supply of goods or services for a
known price.
• In WCF context, it’s an agreement between parties that specifies
the message that can be exchanged based on the terms and
conditions.
– Description of the messages that are passed to and from
service endpoints.
– Endpoint must specify the operations it implement and the
data formats it expect. These specifications make up the
Contract.

18. – Types of Contracts:
• Service Contracts
• Data Contracts
• Message Contracts
– Systems should interoperate, so we need a common
platform. So WSDL is chosen.
• Its an XML grammar defines the functionality offered by a
service and the format of messages.
• Defines what services (operations) are available in service.
• It defines the methods, parameter names, parameter data
types and return data types.
– SOAP – Simple Object Access Protocol
• Communication protocol
• Format for sending messages

19. .NET Types  XML XML  .NET Types
.NET CLR
Types
WCF Service inside Host
WCF Client End Points
WCF
Message Service
Handler
– How Contracts convert to CLR Types – 3 stage process
• Client query the service to know ABC’s (endpoints).
• This raises the metadata infrastructure on the service to
generate WSDL and finally the proxy class.
• Finally at runtime, when client calls the service the .NET types
are serialized into XML and sends over wire.

20. – Service Contracts:
• They define the operations performed by service.
• Two Types
– ServiceContract
– OperationContract
• ServiceContract
– Define the Interface.
• OperationContract
– Define the methods inside interface.
• By mentioning the [ServiceContract] & [OperationContract]
they will be exposed in WSDL.

21. – Data Contracts:
• They define which data types are passed to and from service.
• WCF defines implicit contracts for built-in types such as int and
string.
• Can easily define explicit opt-in data contracts for custom types
• Two Types
– DataContract
– DataMember
• DataContract
– Define which calls should be represent in XSD and include in WSDL.
• DataMember
– Define which class members should be represent in XSD and include in
WSDL.
• At runtime, the DataContractSerializer class serializes objects
to XML using the rules defined in [DataContract] &
[DataMember].

22. – Message Contracts:
• Allows the service to interact directly with messages.
• Describe the structure of SOAP messages sent to and from a
service.
• Gives complete control over the SOAP message sent to and from
a service by providing access to the SOAP headers and bodies
directly.
• They define which data types are passed to and from service.
• WCF defines implicit contracts for built-in types such as int and
string.
• Can easily define explicit opt-in data contracts for custom types
• Two Types
– DataContract
– DataMember
• DataContract
– Define which calls should be represent in XSD and include in WSDL.