IActivityEventListener custom activity

I have created a custom activity implementing IActivityEventListener

interface. Then a EventArgs derived class which delivers the queue message.

Then, from host application I send a queue item to the workflow calling the workflowinstance's EnqueueItem method : how can I intercept the message in the OnEvent method instead of Execute method

I have also tried to create the custom activity as IEventActivity to be hosted inside an EventDrivent one, but the effect is still the same: only Execute method is called when message is received.

Thank you very much in advance.

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IActivityEventListener custom activity

Terry Smith
I rebuilt it and I confirm I cannot drag and drop it in any composite/stateinitialization activity or other than EventDriven activity.
Zafar Ullah
Great!
BioGeek
Hi,

The following show how to combine both IEventActivity and IActivityEventListener

Public Class Activity1

Inherits Activity

Implements IEventActivity, IActivityEventListener(Of QueueEventArgs)

Public Sub OnEvent(ByVal sender As Object, ByVal e As QueueEventArgs) Implements IActivityEventListener(Of QueueEventArgs).OnEvent

Dim executionContext As ActivityExecutionContext = CType(sender, ActivityExecutionContext)

Dim wqs As WorkflowQueuingService = executionContext.GetService(Of WorkflowQueuingService)()

Dim queue As WorkflowQueue = wqs.GetWorkflowQueue(QueueName)

Dim item As Object = queue.Dequeue()

' ToDo: Implement

executionContext.CloseActivity()

End Sub

Protected Overrides Function Execute(ByVal executionContext As ActivityExecutionContext) As ActivityExecutionStatus

Dim status As ActivityExecutionStatus

If IsInEventActivityMode Then

status = ActivityExecutionStatus.Closed

Else

InternalSubscribe(executionContext, Me, False)

status = ActivityExecutionStatus.Executing

End If

Return status

End Function

Public ReadOnly Property QueueName() As IComparable Implements IEventActivity.QueueName

Get

Return "MyQueueName"

End Get

End Property

Public Sub Subscribe(ByVal parentContext As ActivityExecutionContext, ByVal parentEventHandler As IActivityEventListener(Of QueueEventArgs)) Implements IEventActivity.Subscribe

InternalSubscribe(parentContext, parentEventHandler, True)

End Sub

Public Sub Unsubscribe(ByVal parentContext As ActivityExecutionContext, ByVal parentEventHandler As IActivityEventListener(Of QueueEventArgs)) Implements IEventActivity.Unsubscribe

End Sub

Private Sub InternalSubscribe(ByVal executionContext As ActivityExecutionContext, ByVal eventHandler As IActivityEventListener(Of QueueEventArgs), ByVal eventActivityMode As Boolean)

Dim wqs As WorkflowQueuingService = executionContext.GetService(Of WorkflowQueuingService)()

Dim queue As WorkflowQueue = wqs.CreateWorkflowQueue(QueueName, True)

queue.RegisterForQueueItemAvailable(eventHandler, QualifiedName)

IsInEventActivityMode = eventActivityMode

End Sub

Public Shared IsInEventActivityModeProperty As DependencyProperty = DependencyProperty.Register("IsInEventActivityMode", GetType(Boolean), GetType(Activity1))

<Description("This is the description which appears in the Property Browser")> _

<Category("This is the category which will be displayed in the Property Browser")> _

<Browsable(True)> _

<DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)> _

Public Property IsInEventActivityMode() As Boolean

Get

Return (CType((MyBase.GetValue(Activity1.IsInEventActivityModeProperty)), Boolean))

End Get

Set(ByVal Value As Boolean)

MyBase.SetValue(Activity1.IsInEventActivityModeProperty, Value)

End Set

End Property

End Class

Maurice
cgraus
You need to call queue.RegisterForQueueItemAvailable(me) when you are creating the queue and return ActivityExecutionStatus.Executing from the Execute function. Then the OnEvent will be executed as soon as an event occurs.

Public class Activity1

Inherits Activity

Implements IActivityEventListener(Of QueueEventArgs)

Public Sub OnEvent(ByVal sender As Object, ByVal e As System.Workflow.ComponentModel.QueueEventArgs) Implements System.Workflow.ComponentModel.IActivityEventListener(Of System.Workflow.ComponentModel.QueueEventArgs).OnEvent

Dim context As ActivityExecutionContext

context = CType(sender, ActivityExecutionContext)

context.CloseActivity()

End Sub

Protected Overrides Sub Initialize(ByVal provider As System.IServiceProvider)

Dim context As ActivityExecutionContext

context = CType(provider, ActivityExecutionContext)

Dim wqs As WorkflowQueuingService = context.GetService(Of WorkflowQueuingService)()

Dim queue As WorkflowQueue = wqs.CreateWorkflowQueue("MyQueueName", True)

queue.RegisterForQueueItemAvailable(Me, QualifiedName)

MyBase.Initialize(provider)

End Sub

Protected Overrides Function Execute(ByVal executionContext As System.Workflow.ComponentModel.ActivityExecutionContext) As System.Workflow.ComponentModel.ActivityExecutionStatus

Return ActivityExecutionStatus.Executing

End Function

End Class

Maurice
claydevin
I have followed your example, but the workflow designer doesn't permit me to drag and drop this activity like a normal code activity. How can I do that

Thank you!
Nick__A.
Exposing the custom activity also as IEventActivity:

i.e.

public partial class MyEventActivity: Activity, IEventActivity, IActivityEventListener<QueueEventArgs>
{

...

}

is there a similar way to pass throught the OnEvent method once the event is pushed into the workflow queue

Thank you!
clint 2
Did you rebuild your code

I can drag the activity just fine from the toolbox into the workflow and once there move it around using drag and drop.

Maurice
WXS123
You cannot add an activity that implements IEventActivity to a StateInitializationActivity as that would cause the state transition to pause while trying to active a state. They should be added to an EventDrivenActivity to trigger that event.

Maurice
IActivityEventListener custom activity

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