Subscribe to OPC item. Specify machine name, server class, item ID, requested update rate, and a state object.
Syntax
'Declaration
<ExtensionAttribute()>
Public Overloads Shared Function SubscribeItem( _
ByVal As IEasyDAClient, _
ByVal As String, _
ByVal As String, _
ByVal As String, _
ByVal As Integer, _
ByVal As Object _
) As Integer
'Usage
Dim client As IEasyDAClient
Dim machineName As String
Dim serverClass As String
Dim itemId As String
Dim requestedUpdateRate As Integer
Dim state As Object
Dim value As Integer
value = IEasyDAClientExtension.SubscribeItem(client, machineName, serverClass, itemId, requestedUpdateRate, state)
Parameters
- client
- The client object that will perform the operation.
This is typically the EasyDAClient object.
The value of this parameter cannot be null
(Nothing
in Visual Basic).
- machineName
- Name of the machine (empty string for local computer).
The value represents a UNC or DNS computer name. Any string can be passed to this parameter (i.e. will not cause System.ArgumentException), but not all values make sense and will work when an operation using them is attempted. IPv6 addresses are normally enclosed between '[' and ']'.
The value of this parameter cannot be null
(Nothing
in Visual Basic).
- serverClass
- Contains ProgID of the OPC server.
The value of this parameter cannot be null
(Nothing
in Visual Basic).
- itemId
- ID of the item that will be subscribed to.
The value of this parameter cannot be null
(Nothing
in Visual Basic).
- requestedUpdateRate
- How often should the updates be received (number of milliseconds)
- state
- The state object (can be any object supplied by your code); available in event notifications.
The value of this parameter can be null
(Nothing
in Visual Basic).
Return Value
The method returns an integer handle that uniquely identifies the item subscription.
Exceptions
Exception | Description |
System.ArgumentNullException |
A null reference (Nothing in Visual Basic) is passed to a method that does not accept it as a valid argument.
This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception. |
System.ArgumentOutOfRangeException |
The value of an argument is outside the allowable range of values as defined by the invoked method.
This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception. |
Requirements
Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows
See Also