Windows Workflow - An introduction

WINDOWS WORKFLOW

- AN INTRODUCTION

Mahesh Krishnan Senior Consultant, Readify

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Agenda

Introduction to Windows WorkflowWhat is it? What are activities?Hosting

Out of the box Activities Custom Activities and Dependency Properties Handling faults WF Persistence and Tracking

Introduction to WF

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What is WF? Stands for Windows Workflow Foundation (not WWF) One of the 4 pillars of .NET 3.0 WF provides:

A programming model for building Application workflows A runtime to host them

Windows Workflow Foundation

Two types of workflows:SequentialState machine

Visual Studio provides us the tooling support to create Workflows easily

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Activities Activities are building blocks of a WF To a workflow, an activity is a re-usable

program statement An activity that contains other activities

is called a Composite Activity Examples of out of the box activities:

SequenceActivityCodeActivityIfElseActivityWhileActivity

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WF Program A Workflow program is nothing but a

tree of activities WF programs typically wait for some

kind of an input and performs a bunch of activities

Once an activity finishes execution, the next activity in the WF is executed

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Creating workflows Can be created Declaratively (using

XAML) Imperatively via code

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Hosting The program is hosted via WorkflowRuntime

class Can be hosted in any .NET App

WinForms, Console, ASP.NET, WPF... Integrates with other MS technologies –

SharePointBizTalkWCF

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Simple Workflow Example (using Code

Activity)

Demonstration

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Things to cover IDE

Design surfaceProperties windowDocument Outline

Sample Workflow using Code activity Debugging experience

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Out of the box Activities

More on Activities

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Activities for Flow Control IfElseActivity WhileActivity ParallelActivity ConditionedActivityGroup (or CAG) Replicator TerminateActivity SuspendActivity InvokeWorkflowActivity

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Activities for State Management StateActivity SetStateActivity StateInitializationActivity StateFinalizationActivity

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Activites for Event Handling ListenActivity EventDrivenActivity EventHandlersActivity EventHandlingScopeActivity

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Out of the box Activities (contd) Heaps of others:

Activities for Calling web servicesTransaction handlingCompensationFault handlingSynchronizationCalling other workflowsetc

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Out of the box Activities

Demonstration

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Custom ActivitiesCreating your own activities

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Custom Activities Alternative to Code activity Derived from Activity class (or

something derived from it, like SequenceActivity)

Need to over ride Execute method Promotes re-use and is more testable Used from the designer Sometimes increases complexity

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Dependency Properties Properties in Custom activities are usually

implemented as Dependency Property Unlike normal properties, value is not stored

in an instance variable They are registered with Dependency

Property Framework and supports these scenarios:Activity BindingAttached propertiesMeta properties

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Dependency Property declaration

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public static DependencyProperty CardNumberProperty = DependencyProperty.Register("CardNumber", typeof(string), typeof(ENettActivity));

[DescriptionAttribute(“The Credit Card number of user")][CategoryAttribute(“Credit Card Details")][BrowsableAttribute(true)][DesignerSerializationVisibilityAttribute(DesignerSerializationVisibility.Visible)]public string CardNumber{

get { return ((string)(base.GetValue(ENettActivity.CardNumberProperty))); }set { base.SetValue(ENettActivity.CardNumberProperty, value); }

}

Custom ActivityDemonstration

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Handling Faults

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Faults Faults can occur at any time in a WF:

Exceptions thrownActivity failuresThrow statements in code activitiesThrow Activity in WF

If a fault occurs and is not handled, then the WF terminates

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Fault handling try/catch blocks within code will work In custom activities, the HandleFault

method can be overridden to do clean ups

FaultHandlers and FaultHandler Activity can be used to handle specific Exceptions

Throw Activity can be used to throw Exceptions

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Handling FaultsDemonstration

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Workflow Persistence

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Why do you need it? Typically Workflows are long running You may want to maintain the state of

workflows between machine shutdowns You may want to unload workflow

(dehydration) that is idle Scalability and Resource consumption

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Persistence in Windows Workflow Implemented as an optional core service A Sql Server persistence service is

available out of the box The database can be created using

scripts from the directory - [...]\Framework\v3.0\Windows Workflow Foundation\SQL\en

The service can be added easily via configuration or via code

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Tracking Workflows

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Why do you need it? There may be lots of workflows running,

each in a different state You may want to track these workflows

and activities at runtime You may also want to find out what path

a certain Workflow instance took

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Tracking in Windows Workflow WF Tracking Framework allows

monitoring of workflows by capturing events raised during WF execution

SqlTracking service is used to write this to SQL Server database

Like the persistence service, this can be added easily via configuration or code

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Summary

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Summary Windows Workflow provides the runtime

and API to create workflows in .NET Activities are the building blocks of WF .NET provides a whole bunch of ready-

to-use activities, but custom activities can also be created

Persistence services are needed for long running workflows

Tracking services can also be added to track the running of workflows

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Questions?

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