Constant<TValue>(UADataVariable,UAAttributeData<TValue>) Method

Makes constant data variable using generic-typed attribute data object (typed value, status code, timestamp).

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function Constant(Of TValue)( _
   ByVal dataVariable As UADataVariable, _
   ByVal attributeData As UAAttributeData(Of TValue) _
) As UADataVariable

'Usage
 
Dim dataVariable As UADataVariable
Dim attributeData As UAAttributeData(Of TValue)
Dim value As UADataVariable
 
value = UADataVariableExtension.Constant(Of TValue)(dataVariable, attributeData)

[Extension()]
[NotNull()]
public static UADataVariable Constant<TValue>( 
   UADataVariable dataVariable,
   UAAttributeData<TValue> attributeData
)

[Extension()]
[NotNull()]
public:
static UADataVariable^ Constantgeneric<typename TValue>
( 
   UADataVariable^ dataVariable,
   UAAttributeData<TValue^>^ attributeData
)

Parameters

dataVariable: The data variable that will be modified and returned.
The value of this parameter cannot be null (Nothing in Visual Basic).
attributeData: The constant attribute data that will be provided by the data variable.
The value of this parameter cannot be null (Nothing in Visual Basic).

Type Parameters

TValue: The type of the value of the data variable.

Return Value

Returns the , internally modified as defined by the method.

This method never returns null (Nothing in Visual Basic).

Exceptions

Exception Description

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.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.

Remarks

This method overload infers the OPC data type and value rank of the data variable from the TValue type.

The data variable is made read-only, and its minimum sampling interval is set to System.Threading.Timeout.Infinite, effectively disabling the sampling.

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

Reference

UADataVariableExtension Class
UADataVariableExtension Members
Overload List

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