ReadValueFunction(UADataVariable,TypeCode,Func<Object>) Method

Specifies value type code and read value function, for the pull data provision model.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function ReadValueFunction( _
   ByVal dataVariable As UADataVariable, _
   ByVal valueTypeCode As TypeCode, _
   ByVal readValueFunction As Func(Of Object) _
) As UADataVariable

'Usage
 
Dim dataVariable As UADataVariable
Dim valueTypeCode As TypeCode
Dim readValueFunction As Func(Of Object)
Dim value As UADataVariable
 
value = UADataVariableExtension.ReadValueFunction(dataVariable, valueTypeCode, readValueFunction)

[Extension()]
[NotNull()]
public static UADataVariable ReadValueFunction( 
   UADataVariable dataVariable,
   TypeCode valueTypeCode,
   Func<object> readValueFunction
)

[Extension()]
[NotNull()]
public:
static UADataVariable^ ReadValueFunction( 
   UADataVariable^ dataVariable,
   TypeCode valueTypeCode,
   Func<Object^>^ readValueFunction
)

Parameters

dataVariable: The data variable that will be modified and returned.
The value of this parameter cannot be null (Nothing in Visual Basic).
valueTypeCode: The type of the data variable, expressed as .NET type code (System.TypeCode).
readValueFunction: The read value function, i.e. the function that performs the read operation and returns the value that will be returned to the caller of the OPC UA Read.
The value of this parameter cannot be null (Nothing in Visual Basic).

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.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.
System.ComponentModel.InvalidEnumArgumentException	An invalid enumeration value was used. 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.

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.

System.ComponentModel.InvalidEnumArgumentException

An invalid enumeration value was used.

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

Reference

UADataVariableExtension Class
UADataVariableExtension Members
Overload List

Documentation Home, Send Feedback. Resources: Knowledge Base, Product Downloads. Technical support: Online Forums, FAQ.

Missing some example? Ask us for it on our Online Forums! You do not have to own a commercial license in order to use Online Forums, and we reply to every post.