OPC Studio User's Guide and Reference
SubscribeItem(IEasyDAClient,DAItemGroupArguments) Method



OpcLabs.EasyOpcClassicCore Assembly > OpcLabs.EasyOpc.DataAccess Namespace > IEasyDAClientExtension Class > SubscribeItem Method : SubscribeItem(IEasyDAClient,DAItemGroupArguments) Method
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).

Arguments specifying how to subscribe to an OPC DA item.

The value of this parameter cannot be null (Nothing in Visual Basic).

Subscribe to OPC item using an object that holds all necessary arguments.
Syntax
'Declaration
 
<ExtensionAttribute()>
Public Overloads Shared Function SubscribeItem( _
   ByVal client As IEasyDAClient, _
   ByVal itemGroupArguments As DAItemGroupArguments _
) As Integer
'Usage
 
Dim client As IEasyDAClient
Dim itemGroupArguments As DAItemGroupArguments
Dim value As Integer
 
value = IEasyDAClientExtension.SubscribeItem(client, itemGroupArguments)

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).

itemGroupArguments
Arguments specifying how to subscribe to an OPC DA item.

The value of this parameter cannot be null (Nothing in Visual Basic).

Return Value

The method returns an integer handle that uniquely identifies the item subscription.
Exceptions
ExceptionDescription

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.

Remarks

This is an extension method (info: C#, VB.NET). In languages that have support for extensions methods (such as C# and VB.NET), you can use the extension method as if it were a regular method on the object that is its first parameter. In other languages (such as with Python.NET), you will call the extension as a static method, and pass it the object on which it acts as its first parameter.

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