Dim EasyAEClient As New OpcLabs.EasyOpc.AlarmsAndEvents.EasyAEClient Dim myState As OpcLabs.EasyOpc.AlarmsAndEvents.AEConditionState Dim myFilter As OpcLabs.EasyOpc.AlarmsAndEvents.AESubscriptionFilter Dim myAttributesForSelectedCategories As OpcLabs.EasyOpc.AlarmsAndEvents.AEAttributeSetDictionary Dim myFilterCategories() As Long = Nothing Dim MyHandle As Integer myState = New OpcLabs.EasyOpc.AlarmsAndEvents.AEConditionState myFilter = EasyAEClient.CreateSubscriptionFilter myAttributesForSelectedCategories = New OpcLabs.EasyOpc.AlarmsAndEvents.AEAttributeSetDictionary myAttributesForSelectedCategories = ... doing some stuff to fill that variable myFilterCategories = {1, 2, 3} myFilter.Categories = myFilterCategories ''myFilter.Sources = {"computer.clock.timer"} ... works fine if I use this instead of setting myFilter.Categories AddHandler EasyAEClient.Notification, AddressOf EasyAEClient_Notification MyHandle = EasyAEClient.SubscribeEvents(“physicalServerName”, “OPCAEServerName”, 1000, myState, myFilter, myAttributesForSelectedCategories) Private Sub EasyAEClient_Notification(ByVal sender As Object, ByVal e As OpcLabs.EasyOpc.AlarmsAndEvents.EasyAENotificationEventArgs) ''This is where e.Exception has the value “{[12585986] *** System.ArgumentException: The parameter is incorrect. }“ End Sub