Generic server callback method.
Add an item in the generic server cache.
This method is typically called during the execution of the CreateServerItems or ValidateItems methods, but it can be called anytime an item needs to be added to the generic server cache.
Item that are added to the generic server cache can be accessed from the OPC clients.
Syntax
Visual Basic (Usage) | Copy Code |
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Dim AppItemHandle As Integer
Dim ItemId As String
Dim AccessRights As Integer
Dim InitValue As Object
Dim quality As Short
Dim timestamp As Date
Dim scanRate As Integer
Dim value As Integer
value = GenericServer.AddItem(AppItemHandle, ItemId, AccessRights, InitValue, quality, timestamp, scanRate) |
Parameters
- AppItemHandle
- Handle defined int the adaptation assembly to reference the item.
This handle is passed as an item identifier in calls between the generic server and the customization plugin. It should be chosen so that it allows fast access to the item data. - ItemId
- Fully qualified item name. The OPC clients use this name to access the item.
This is a fully qualified item identifier such as "device1.channel5.heater3". The generic server part builds an appropriate hierarchical address space.
Note that the separator character ( . in the above sample identifier ) must match the separator character specified in the GetServerParameters method! - AccessRights
- Access rights as defined in the OPC specification: OPC.READABLE , OPC.WRITEABLE , OPC.READWRITEABLE
- InitValue
- Object with initial value and the item's canonical data type.
A value must always be specified for the canonical data type to be defined. - quality
- Initial quality of the item. This is a short value ( Int16) with the value of the OPCQuality enumerator.
- timestamp
- Initial timestamp
- scanRate
- Scan rate for this item in ms. A value of -1 indicates and undefined value.
This argument is used only be the generic server Professional Edition to optimize the item refresh.
Return Value
Returns S_OK if the item was successfully added to the cache.
Requirements
Target Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, Windows Vista, Windows Server 2008 family
See Also