Option Explicit On
Option Strict On
 
Imports OpcLabs.EasyOpc.DataAccess
 
Public Class Form1
 
    ' Called whenever one or more subscribed items change
    Private Shared Sub EasyDAClient1_MultipleItemsChanged(sender As Object, e As EasyDAMultipleItemsChangedEventArgs) Handles EasyDAClient1.MultipleItemsChanged
        Dim count As Integer = e.ArgsArray.Length
        For i As Integer = 0 To count - 1
            Dim eventArgs As EasyDAItemChangedEventArgs = e.ArgsArray(i)
            ' We have passed the reference to the associated ListVeiwItem in a State argument when subscribing
            Dim listViewItem As ListViewItem = CType(eventArgs.State, ListViewItem)
            UpdateListViewItem(listViewItem, eventArgs.Exception, eventArgs.Vtq)
        Next
    End Sub
 
    ' Updates ListViewItem (from reading or change notification) with exception and value/timestamp/quality
    Private Shared Sub UpdateListViewItem(ByVal listViewItem As ListViewItem, ByVal exception As Exception, ByVal vtq As DAVtq)
        Dim vtqText As String = ""
        Dim exceptionText As String = ""
 
        If (Exception Is Nothing) Then
            vtqText = vtq.ToString()
        Else
            exceptionText = Exception.Message
        End If
 
        listViewItem.SubItems(1).Text = vtqText
        listViewItem.SubItems(2).Text = exceptionText
    End Sub
 
    ' IsSubscribed setter takes care of enabling/disabling the user interface elements
    Protected Property IsSubscribed As Boolean
        Get
            Return _subscribed
        End Get
        Set(value As Boolean)
            Dim oldValue As Boolean = _subscribed
            _subscribed = value
            If (_subscribed <> oldValue) Then
                UpdateButtons()
            End If
        End Set
    End Property
 
    Private Sub ReadButton_Click(sender As Object, e As EventArgs) Handles ReadButton.Click
        ' Prepare an array describing what we want to read and how
        Dim count As Integer = ItemsListView.Items.Count
        Dim argumentsArray(count - 1) As DAReadItemArguments
        For i As Integer = 0 To count - 1
            Dim listViewItem As ListViewItem = ItemsListView.Items(i)
            Dim itemId As String = listViewItem.Text
            argumentsArray(i) = New DAReadItemArguments("OPCLabs.KitServer.2", itemId, 50)
        Next
 
        ' Execute the Read operation
        Dim resultsArray() As DAVtqResult = EasyDAClient1.ReadMultipleItems(argumentsArray)
 
        ' Go through the result array, and update the list view items
        For i As Integer = 0 To count - 1
            UpdateListViewItem(ItemsListView.Items(i), resultsArray(i).Exception, resultsArray(i).Vtq)
        Next
    End Sub
 
    Private Sub SubscribeButton_Click(sender As Object, e As EventArgs) Handles SubscribeButton.Click
        IsSubscribed = True
 
        ' Prepare an array describing what we want to subscribe to and how
        Dim count As Integer = ItemsListView.Items.Count
        Dim argumentsArray(count - 1) As DAItemGroupArguments
        For i As Integer = 0 To count - 1
            Dim listViewItem As ListViewItem = ItemsListView.Items(i)
            Dim itemId As String = listViewItem.Text
            ' We use the last argument (State) to provide a reference to the associated ListViewItem
            argumentsArray(i) = New DAItemGroupArguments("OPCLabs.KitServer.2", itemId, 100, listViewItem)
        Next
 
        ' Execute the Subscribe operation
        EasyDAClient1.SubscribeMultipleItems(argumentsArray)
    End Sub
 
    Private Sub UnsubscribeButton_Click(sender As Object, e As EventArgs) Handles UnsubscribeButton.Click
        IsSubscribed = False
 
        ' Execute the Unsubscribe operation
        EasyDAClient1.UnsubscribeAllItems()
    End Sub
 
    Private Sub UpdateButtons()
        ReadButton.Enabled = Not IsSubscribed
        SubscribeButton.Enabled = Not IsSubscribed
        UnsubscribeButton.Enabled = IsSubscribed
    End Sub
 
    Private _subscribed As Boolean
End Class
 

    Private Sub ReadButton_Click(sender As Object, e As EventArgs) Handles ReadButton.Click
 
        Dim count As Integer = ItemsListView.Items.Count
        Dim argumentsArray(count - 1) As DAReadItemArguments
 
        For i = 0 To count - 1
            Dim listViewItem As ListViewItem = ItemsListView.Items(i)
            Dim itemId As String = listViewItem.Text
            argumentsArray(i) = New DAReadItemArguments("OPCLabs.KitServer.2", itemId, 50)
        Next
 
        Dim resultsArray() As DAVtqResult = EasyDAClient1.ReadMultipleItems(argumentsArray)
 
        For i = 0 To count - 1
            Dim listViewItem As ListViewItem = ItemsListView.Items(i)
            Dim vtqResult As DAVtqResult = resultsArray(i)
 
            Dim vtqText As String = ""
            Dim exceptionText As String = ""
 
            If (vtqResult.Exception Is Nothing) Then
                vtqText = vtqResult.Vtq.ToString()
            Else
                exceptionText = vtqResult.Exception.Message
            End If
 
            listViewItem.SubItems(1).Text = vtqText
            listViewItem.SubItems(2).Text = exceptionText
        Next
 
    End Sub