Subscribing to Events

For example, a time event can be set up to recur every 30 seconds, and the form display the time of the most recent event. The code is as follows:

Imports System
Imports System.Collections.Generic
Imports System.Windows
Imports Proficy.Platform.Core.Cdo.Connections
Imports Proficy.Platform.Core.ClientTools.ServiceDirectory
Imports Proficy.Platform.Core.ProficySystem.MobileObject
Imports Proficy.Platform.Core.ProficySystem.Types
Imports Proficy.Platform.Samples.Forms.Base

Public Class EventVB
    Inherits BaseFormVB.Proficy.Platform.Samples.Forms.Base.VB.BaseFormVB

    Public Overloads Overrides Sub TransferDataIn()
        ' The published Time Event to subscribe to is coming from Workflow via an input parameter in this case.
        SubscribeToEvent(_directoryResource.LdapAddress )
    End Sub

    Private Sub SubscribeToEvent(ByVal eventLdapAddress As String)
        Dim userStartup As UserStartup = userStartup.[Default]
        Dim serviceProvider As IServiceProvider = New BasicServicesProvider(userStartup.ServiceDirectory)
        Dim subscription As New DirectoryAddressableSubscription(serviceProvider, eventLdapAddress)
        ' Note: DirectoryAddressableSubscription has been renamed to Subscription
        AddHandler subscription.EventOccurred, AddressOf subscription_EventOccurred
        subscription.Subscribe()
    End Sub

    Private Sub subscription_EventOccurred(ByVal sender As Object, ByVal e As EventOccurredEventArgs)
        ' This is called when the event occurs, and the EventArgs may be used to adjust the 
        ' values of display objects, or to set output parameter values. In this case we have a 
        ' recurring event,and we update a text block with the time of the latest event, changing 
        ' color alternately between red and blue.
        Dim newText As String = DateTime.Now.ToString()
        EventTimeText.Text = newText
        If EventTimeText.ForeColor = System.Drawing.Color.Red Then
            EventTimeText.ForeColor = System.Drawing.Color.Blue
        Else
            EventTimeText.ForeColor = System.Drawing.Color.Red
        End If
        EventTimeText.Refresh()
    End Sub
        [InputProperty("EventToSubscribe", "Event to Subscribe to", "The time event to subscribe to")]
                   protected DirectoryResource _directoryResource = null;
End Class

This technique can be generalized for any item that can be subscribed to; however, the EventOccurredEventArgs will contain different information depending on the type of event. In the above example, this information is ignored, but in general the information can be extracted and displayed in the form.

Common subscribable items are:

• equipment properties
• time events
• condition events
• new work request events
• work request status changed events
• workflow task expired events
• workflow task step expired events

In each case the LDAP address of the item must be located in the DirectoryViewer, and then copied and pasted as an argument into the SubscribeToEvent call.

Private Sub subscription1_EventOccurred(ByVal sender As Object, ByVal e As EventOccurredEventArgs)
        Dim message As MobileMessage = e.EventMessage
        Dim dataItemEvent As DataItemChangedEvent =  TryCast(message.ObjectInstance, DataItemChangedEvent)
        Dim newValue As ProcessValue = dataItemEvent.NewValue
SomeLabel.Text = newValue.ToString()
    End Sub

Display Time Event Data Example

Private Sub subscription1_EventOccurred(ByVal sender As Object, ByVal e As EventOccurredEventArgs)
      Dim eventInfo As TimeEvent = TryCast(e.EventData("EventData").GetObject(), TimeEvent)
        SomeLabel.Text = eventInfo.Description
    End Sub