Windows Workflow Foundation (WWF)

Requirement

1. Visual Studio 2005 Version 8.0.50727.42 
2. .Net Framework 3.0 or above

3. Visual Studio extensions for workflow (file: Visual Studio 2005 Extensions for Windows Workflow Foundation (EN).exe): http://www.microsoft.com/downloads/details.aspx?familyid=5D61409E-1FA3-48CF-8023-E8F38E709BA6&displaylang=en

Workflow Types

• Sequential workflow
  • Good for business process
  • Not so good for user interaction
• State machinen workflow
  • Good for lots of user interactions
• Rule driven workflow, based on sequential workflow
  • More complicate and costly

Two types of activities

• Composite activities
  • Contains other activities, e.g. sequential acitivities
• Basic activities
  • Does the actual work 

System.Workflow.Runtime.WorkFlowRuntime object

• Properties
  • IsStarted
• Methods
  • AddService
  • CreateWorkflow
  • StartRuntime
  • StopRuntime
• Events
  • Started
  • Stopped
  • WorkflowCompleted
  • WorkflowIdled
  • WorkflowTerminated

WorkflowInstance object

• Properties
  • InstanceId
  • WorkflowRuntime
• Methods
  • ApplyWorkflowChanges
  • GetWorkflowDefinition
  • Resume
  • Start
  • Suspend
  • Terminate: instance.Terminate("User cancellation.");
• Events
• Status: workflowInstance.GetWorkflowDefinition().ExecutionStatus.ToString();

Activity object

• Properties
  • Description
  • Enabled
  • ExecutionResult
  • ExecutionStatus
  • ActivityExecutionStatus
  • Name
  • Parent
  • WorkflowInstanceId
• Methods (they are all protected virtual methods)
  • Cancel
  • Clone
  • Execute
  • GetActivityByName
  • Load
  • RaiseEvent
  • RaiseGenericEvent<T>
  • Save
• Events 

ActivityExecutionContext class

• Created by workflow runtime
• Provide info about workflow instance
  • Initialization
  • Timers
  • General execution flow

Sequence Activity Object

• Is a composite activity 

Code Activity

Throw/FaultHandler Activities

• Each FaultHandler is designed to handle one, and only one, exception type.

Suspend Activity

Terminate Activity

• Difference from workflow termination by unhandled exception
  • WorkflowTerminatedEventArgs.Exception is of the type System.Workflow. ComponentModel.WorkflowTerminatedException

Workflow interprocess communication

• WF uses an abstraction layer to buffer workflow from host
  • Local communication service
  • Need to add ExternalDataService to workflow runtime?
• Create a workflow data communicaiton interface
• Annotate with [ExternalDataExchange] (marker interface for local communication service)
  
public interface IMVDataService
{
[ExternalDataExchange]
void MVDataUpdate (DataSet mvData);
}
• Create a workflow data event argument class
  
[Serializable]
public class MVDataAvailableArgs : ExternalDataEventArgs
{
public MVDataAvailableArgs(Guid instanceId)
: base(instanceId)
{
}
}


Pluggable services

• Additonal software functions that your workflow can use to complete their tasks
• Some are optional and some are required
• They are pluggable
• Base workflow services
  • WorkflowPersistenceService
  • WorkflowQueuingService
  • WorkflowRuntimeService
  • WorkflowSchedulerService
    • DefaultWorkflowSchedulerService
    • ManualWorkflowSchedulerService
  • WorkflowSubscriptionService
  • WorkflowTransactionService
  • TrackingService
    • SqlTrackingService
      • Can use Workflowmonitor to query
      • Tracking specification objects
      • Tracking retrieval objects
        • Example 
          • SqlTrackingQuery
        • Activity events
          • ActivityTrackingPoint
          • ActivityTrackingLocation
        • Workflow events
        • User events
      • Tracking records are decorated with annotations
      • Tracking level determined in tracking profile
        • XML doc
    • ConsoleTrackingService
    • SimpleFileTrackingService

Pass Dictionary object as a parameter to workflow instance

• In the activity class
  
public sealed partial class Workflow1: SequentialWorkflowActivity
{
private Int32 _delay = 10;public Workflow1()
{
InitializeComponent();
}// Receives value from parameter
public Int32 Delay
{
get { return _delay; }
set
{
if (value < 0 || value > 120)
{
value = 10;
}
if (ExecutionStatus == ActivityExecutionStatus.Initialized)
{
_delay = value;
delayActivity1.TimeoutDuration = new TimeSpan(0, 0, _delay);
}
}
}private void PreDelayMessage(object sender, EventArgs e)
{
MessageBox.Show("Pre-delay code is being executed.");
}private void PostDelayMessage(object sender, EventArgs e)
{
MessageBox.Show("Post-delay code is being executed.");
}
}
• In the main program
  
class Program
{
private static AutoResetEvent _waitHandle = new AutoResetEvent(false);
static void Main(string[] args)
{
WorkflowRuntime wfr = WorkflowFactory.GetWorkflowRuntime();
wfr.WorkflowIdled +=
new EventHandler(wfr_WorkflowIdled);
wfr.WorkflowCompleted +=
new EventHandler(wfr_WorkflowCompleted);
wfr.WorkflowTerminated +=
new EventHandler(wfr_WorkflowTerminated);Int32 delay = 0;
string val = args.Length > 0 ? args[0] : "10";
if (!Int32.TryParse(val, out delay))
{
Console.WriteLine("You must pass in an integer value.");
return;
}// Constructs a Dictionary object as workflow instance parameter
Dictionary prms = new Dictionary();
prms.Add("Delay", delay);Console.WriteLine("Waiting for workflow completion ({0} seconds).", val);WorkflowInstance wfi =
// Pass the Dictionary object as parameter
wfr.CreateWorkflow(typeof(LongRunningWorkflow.Workflow1), prms);
wfi.Start();
_waitHandle.WaitOne();
Console.WriteLine("Done.");
}
static void wfr_WorkflowTerminated(object sender, WorkflowTerminatedEventArgs e)
{
Console.WriteLine("Workflow terminated.");
_waitHandle.Set();
}
static void wfr_WorkflowIdled(object sender, WorkflowEventArgs e)
{
Console.WriteLine("Workflow idled.");
}static void wfr_WorkflowCompleted(object sender, WorkflowCompletedEventArgs e)
{
Console.WriteLine("Workflow completed.");
_waitHandle.Set();
}
}