WCF Intro

Scott ReedOwner - Brain Hz Software

scott@brainhzsoftware.comInstructor – DevelopMentor

scottr@develop.com

Agenda

• Why WCF?• Architecture• Programmatic client and service• Moving to configuration• Sharing contracts• Summary

Before WCFTechnology Pros Cons

Sockets Flexible Code everything

RPC Imperative request/reply Simplistic, synchronous

DCOM Trxs, Security Complex, hard to debug/maintain

.NET Remoting Easy, configurable, extensible

No interoperability

ASMX Web Services Easy, interoperable Simplistic, Security=SSL only

WSE 2.0/3.0 Added message security Not as easy, Verbose, still lacking

MSMQ Async, solves availability Explicit message passing

Clearly not an enabling technology, instead it is unifying

WCF Design goal

• Design goal:– To be the best way to get any two pieces of

software to communicate under any circumstances

• To achieve this had to abstract communication– Services are programs that exchange messages– Lower layer sends messages through channels

Messages

• Packaged data• Abstraction of a SOAP message– Xml InfoSet not actually XML

• Created using factory method– Message.CreateMessage

Channels

• Channel transmit those messages• Channels together form a stack• Protocol channels can be layered on top– Provide services like reliability and security

• Encoder changes Message to byte[]• Transport channel actually sends the bytes

Channel Stack

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Encoder

Transport Channel

Protocol

Protocol

Encoder

Transport Channel

Protocol

Protocol

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Programming in the Channel Layer

• Explicit message passing like in sockets or MSMQ– What happened to easy?

void ChannelListen(){ IChannelListener<IReplyChannel> listener = GetListener(); listener.Open();  while (listener.WaitForChannel()) { IReplyChannel channel = listener.AcceptChannel(); channel.Open();  RequestContext request = channel.ReceiveRequest(); Message reply = HandleMessage(request.RequestMessage);  request.Reply(reply); request.Close(); channel.Close();  }}

void ChannelListen(){ IChannelListener<IReplyChannel> listener = GetListener(); listener.Open();  while (listener.WaitForChannel()) { IReplyChannel channel = listener.AcceptChannel(); channel.Open();  RequestContext request = channel.ReceiveRequest(); Message reply = HandleMessage(request.RequestMessage);  request.Reply(reply); request.Close(); channel.Close();  }}

Service Model Layer

• Sits on top of Channel Layer and hides it• Allows method invocation of strongly typed

parameters• Uses serialization to translate objects into

messages

The Big Picture

protocol

protocol

encoder

transport

protocol

protocol

encoder

transport

serializer serializer

proxydispatcher

service objectService Model

Layer

Channel Layer

Endpoint

• Clients talk to endpoints, and services expose endpoints

• Address• Binding• Contract

BC A

BC A

B CA

B CA

B CA

Client Service

Service

WCF in all its glory

Business Partner

Customer

wsHttpBinding(feature rich)

basicHttpBinding(compatibility)

netTcpBinding

(perform

ance)

netMsmqBinding

(batch processing)netNamedPipeBinding

(local, fast)

Browser

webHttpBinding

(AJAX, JSON…)

Hosting

• Need something to listen for incoming connections (a host)

• WCF is host independent (by default)

• Self host (Console, NT Service, Forms/WPF App)– Use the ServiceHost class (Open and Close)

• IIS/WAS hosted– Use a .svc file (just like ASMX)

• WCF provided host for testing *– WcfServiceHost

Step by step

• Define the contract• Implement the contract• Host the service• Expose endpoints• Optionally expose metadata

Demo

• Writing a programmatic client and a service

Configuration

• Why do it in config?– So you don’t have to recompile

• Everything you do in code can be done in config (almost)

Demo (revisited)

• Changing to a config file

Sharing contracts

• Both the client and the service need to know the types and methods listed in the contract

• There are two ways to accomplish this:– Share types (ala Remoting)– Share schema (ala ASMX)

Demo (revisited again)

• Exposing metadata (base and explicit)• Generating a proxy

Summary

• WCF unifies communications technology• Architected in two layers:– Channel layer and Service Model layer

• Endpoints are ABCs• Two ways to share contract (type and schema)