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Mahesh Krishnan, Senior Consultant, Readify

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Agenda

Introduction to WCF

y What is it? Why use it?

y Fundamentals and the ABCs of WCF

y Hosting

Tooling Support

Passing data around in WCF

Handling faults


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Slide 3


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What is WCF?

Stands for Windows Communication Foundation

One of the 4 pillars of .NET 3.0

Microsofts unified programming model (the service

model) for building Service-Oriented Applications


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Windows Communication Foundation

WCF provides:

y an SDK for creating SOA

y a runtime for running Services on Windows

Services send and receive messages

All messages are SOAP messages

WCF takes care of all the plumbing

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Why use WCF?

Interoperable and Standards based

y Supports WS-* protocols

Unified Programming Modely Unifies previous models like .NET Remoting,

ASMX web services, COM+ etc

Productive Programming Model

y Declarative

y Imperative

y Configuration based

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WCF: How does it work?


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WCF End points


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WCF Endpoints

Every service has

Address

yWhere the service isBinding

yHow to talk to the service

ContractyWhat the service can do

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The EndPoint Anology

Address Binding Contract

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Address

Combination of transport, server name,

port & path

Transport is determined by the binding

Exampleshttp://localhost:8001

net.tcp://localhost:8002/MyServicenet.pipe://localhost/MyPipe

net.msmq://localhost/private/MyService

net.msmq://localhost/MyService

Sli


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Out of the box Bindings

BasicHttpBinding

WSHttpBinding

WS2 7HttpBinding

WSDualHttpBinding

WSFederationHttp

Binding

WS2 7FederationHttpBinding

NetTcpBinding

NetNamedPipeBinding

NetMsmqBinding

NetPeerTcpBinding

WebHttpBinding

MsmqIntegrationBinding

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Contracts

Service contracts

y Defines operations, communications and

behaviours.

Data contracts

y Defines data entities and parameter types.

Fault contracts

y Defines error types

Message contracts

y Defines message formats

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Service Contracts

[ServiceContract] Defines a set of operations

[OperationContract] Defines a single method

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[ServiceContract]

public interface IService

{

[OperationContract]

string GetData(int value);

}

public class ConcreteService : IService

{ public string GetData(int value)

{ ... }

public string OtherMethod()

{ ... }

}


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Data Contracts

[DataContract] Specifies type as a data contract

[DataMember] Members that are part of contract

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[DataContract]

public class CustomType

{

[DataMember]

public bool MyFlag { get; set; }

[DataMember]

public string MyString { get; set; }

}


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Metadata Exchange

Service can also expose endpoint for

Metadata Exchange (MEX)

It provides a mechanism for clients to

find out about:

yAddress of other end points

y Bindings that are used

y Contracts used Service, Operation, Data,etc

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Hosting

IIS

y HTTP only

WAS (Windows Activation Service)

y Can use any transport

y Vista and Windows Server 2 8 only

Self hosting

y Can use any transport

y Can be hosted within Console, WinForms,

etc Applications

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ToolingSupport

Visual Studio

y Separate projects forWCF

y Add Service reference menu

y WCF Configuration Editor

y WCF Service Host

y WCF Test Tool

SvcUtil To generate proxies SvcTraceViewer To view logs

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Demonstration

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Passing data around

To pass data across boundaries, they

need to be serialized

.NET Framework already contains an

attribute for serialization

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[Serializable]

public class Person

{

public string LastName;public string FirstName;

}


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Passing data around

SerializableAttribute has some

limitations

y Includes some type information in serialized

data not suited for true SOA

y Does not support aliases

y Does not support versioning

y

Does not support orderingy Explicit opt-out is needed to leave out some

properties that shouldnt be serialized

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Alternative DataContract

DataContract: created specifically for

WCF to serialize types

yAttribute contains Name and Namespace

properties

DataMember is needed to specify which

properties/fields will form part of the

contracty Contains EmitDefaultValue, IsRequired,

Name, Order properties

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DataContract

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[DataContract(Name="Contact")]

public class Person

{

[DataMember(IsRequired=true, Name="SurName")]public string LastName;

public string FirstName; //Not included in contract

}


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Versioning of data contracts

Three different scenarios:

yNew fields have been added

yExisting fields have been deletedyFields have been renamed

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Alternate way of looking at it:

Older version data [v1] passed to

Service accepting newer version of

data [v2]

Newer version data [v2] passed to

Service accepting older version of

data [v1]

New [v2]-> Old [v1]-> New [v2]

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New -> Old -> New

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Proxy code to hold

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[DataContract]

public class MyDataContract : IExtensibleDataObject

{

public ExtensionDataObject ExtensionData

{get; set;

}

}


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Inheritance with Data Contracts

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[DataContract]

public class Employee { ... }

[DataContract]

public class Manager : Employee { ... }

[ServiceContract]

public interface IEmployeeService

{

[OperationContract]

public void AddEmployee(Employee e);}


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Inheritance with Data Contracts

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[DataContract]

[KnownType(typeof(Manager))]

public class Employee { ... }

[DataContract]public class Manager : Employee { ... }

[ServiceContract]


{

[OperationContract]public void AddEmployee(Employee e);

}


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SOAP Faults

Three main kinds of Exceptions can

occur:

y Communication errors

y Unexpected error on the service

y Errors thrown by the service on purpose

.NET Exceptions are technology specific

All Exceptions come across the wire asSOAP Faults

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Faults

In WCF, SOAP faults are passed in as

FaultException objects

Rather than throwing Exceptions,

services should throw FaultExceptions

Or better still FaultException

Throwing FaultExceptions will not fault

the proxy and the channel

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FaultContracts

Specifies what kind of Exceptions, an

operation can throw

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[ServiceContract]


{

[OperationContract]

[FaultContract(typeof(ValidationException))]

public void AddEmployee(Employee e);}


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Server side code

Always throw Exceptions as Fault

Exceptions

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public class EmployeeService

{

public void AddEmployee(Employee e)

{

...

thrownewFaultException(newValidationException(errorMsg));

}

}


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Client side code

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EmployeeServiceProxy proxy = new EmployeeServiceProxy();

try

{

...

proxy.AddEmployee(emp);

}

catch(FaultExceptione)

{

//Dostuffwith exception here

}

catch(FaultException e){

//Will catch all othertypesofFault exceptions...

}


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Exceptions while developing

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...


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Summary

WCF provides a runtime for creating Service Oriented Apps

Provides a productive programming model. Takes care of:

y Messaging and Exchange formats

y All Plumbing: Transaction, Reliability, Security, etc

Supports Declarative (via attributes), Imperative (via code)

and Configuration based (via config files) programming model

ABCs of Endpoints

y Address: Where to go?

y Binding: How to get there?

y Contract: What to do?

Hosting

y IIS, WAS, Self-hosting


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Summary (contd)

ServiceContract and OperationContract specify Service and

operation information

DataContracts and DataMembers are used for specifying the

data that is passed across the wire

Use KnownType attribute for specifying class hierarchy

information in Data contracts

FaultContracts specify what Exceptions may be thrown by the

operations


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