Wcf

ARIANA

Introduction to WCF What is it? Why use it? Architecture Fundamentals and the ABCs of WCF Hosting

Tooling Support Handling faults

Stands for Windows Communication Foundation One of the 4 pillars of .NET 3.0 Microsoft’s unified programming model (the service model) for building Service-Oriented Applications

ServiceSmall program interacted by well defines

message exchangesAgile, Reliable, Stable, Interoperable, Secure

Four TenetsBoundaries are ExplicitServices are AutonomousServices share schema and contract, not classService compatibility is based upon policy

WCF provides:an SDK for creating SOAa runtime for running Services on

Windows Services send and receive messages All messages are SOAP messages WCF takes care of all the plumbing

Interoperable and Standards based Supports WS-* protocols

Unified Programming Model Unifies previous models like .NET

Remoting, ASMX web services, COM+ etc Productive Programming Model

Declarative Imperative Configuration based

Simplicity Flexibility Maintainability Power

Every service has Address

Where the service is Binding

How to talk to the service Contract

What the service can do

Combination of transport, server name, port & path

Transport is determined by the binding Examples

http://localhost:8001net.tcp://localhost:8002/MyServicenet.pipe://localhost/MyPipenet.msmq://localhost/private/MyServicenet.msmq://localhost/MyService

Transport HTTP TCP MSMQ

Message formats and encoding Plain text Binary Message Transmission Optimization Mechanism

(MTOM) Communication security

No security Transport security Message security Authenticating and authorizing callers

BasicHttpBinding WSHttpBinding WS2007HttpBinding WSDualHttpBinding WSFederationHttp

Binding WS2007FederationHttp

Binding

NetTcpBinding NetNamedPipeBinding NetMsmqBinding NetPeerTcpBinding WebHttpBinding MsmqIntegrationBinding

Service contracts Defines operations, communications

and behaviours. Data contracts

Defines data entities and parameter types.

Fault contracts Defines error types

Message contracts Defines message formats

[ServiceContract] – Defines a ‘set’ of operations [OperationContract] – Defines a single method

[ServiceContract]public interface IService{ [OperationContract] string GetData(int value);}

public class ConcreteService : IService{ public string GetData(int value) { ... }

public string OtherMethod() { ... }}

[ServiceContract]public interface IService{ [OperationContract] string GetData(int value);}

public class ConcreteService : IService{ public string GetData(int value) { ... }

public string OtherMethod() { ... }}

[DataContract] – Specifies type as a data contract [DataMember] – Members that are part of

contract

[DataContract]public class CustomType{ [DataMember] public bool MyFlag { get; set; }

[DataMember] public string MyString { get; set; }

}

[DataContract]public class CustomType{ [DataMember] public bool MyFlag { get; set; }

[DataMember] public string MyString { get; set; }

}

DataContract: created specifically for WCF to serialize types Attribute contains Name and Namespace

properties DataMember is needed to specify which

properties/fields will form part of the contract Contains EmitDefaultValue, IsRequired,

Name, Order properties

Service can also expose endpoint for Metadata Exchange (MEX)

It provides a mechanism for clients to find out about: Address of other end points Bindings that are used Contracts used – Service, Operation, Data,

etc

IIS HTTP only

WAS (Windows Activation Service) Can use any transport Vista and Windows Server 2008 only

Self hosting Can use any transport Can be hosted within Console, WinForms,

etc Applications

Visual Studio Separate projects for WCF “Add Service reference” menu WCF Configuration Editor WCF Service Host WCF Test Tool

SvcUtil – To generate proxies SvcTraceViewer – To view logs

Three main kinds of Exceptions can occur: Communication errors Unexpected error on the service Errors thrown by the service on purpose

.NET Exceptions are technology specific All Exceptions come across the wire as SOAP

Faults

In WCF, SOAP faults are passed in as FaultException objects

Rather than throwing Exceptions, services should throw FaultExceptions

Or better still FaultException<T> Throwing FaultExceptions will not fault the

proxy and the channel

Specifies what kind of Exceptions, an operation can throw

[ServiceContract] public interface IEmployeeService { [OperationContract] [FaultContract(typeof(ValidationException))] public void AddEmployee(Employee e); }

[ServiceContract] public interface IEmployeeService { [OperationContract] [FaultContract(typeof(ValidationException))] public void AddEmployee(Employee e); }

Its made of a lot of different components, so you can create new components for security, transport, authentication.

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.

Its faster than ASMX Its Interoperability, for java, and more. WCF is interoperable with other services when

compared to .Net Remoting, where the client and service have to be .Net

WCF services provide better reliability and security in compared to ASMX web services.

WCF is Microsoft's implementation of SOA and hence its APIs are solely controlled by MS which makes interoperability a bit difficult.

To deploy WCF apps, need more underlying hardware resources on the platform on which the WCF applications will be running, since there is an additional layer of abstraction to deal with.

WCF provides a runtime for creating Service Oriented Apps Provides a productive programming model. Takes care of:

Messaging and Exchange formats All Plumbing: Transaction, Reliability, Security, etc

Supports Declarative (via attributes), Imperative (via code) and Configuration based (via config files) programming model

ABCs of Endpoints Address: Where to go? Binding: How to get there? Contract: What to do?

Hosting IIS, WAS, Self-hosting