OPC Studio User's Guide and Reference
ReadFunction(UADataVariable,TypeCode,Func<UAAttributeData>) Method



OpcLabs.ServerOpcUA Assembly > OpcLabs.EasyOpc.UA.NodeSpace Namespace > UADataVariableExtension Class > ReadFunction Method : ReadFunction(UADataVariable,TypeCode,Func<UAAttributeData>) Method
The data variable that will be modified and returned.

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

The type of the data variable, expressed as .NET type code (System.TypeCode).
The read function, i.e. the function that performs the read operation and returns the attribute data that will be returned to the caller of the OPC UA Read.

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

Specifies value type code, and read function returning attribute data, for the pull data provision model.
Syntax
'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function ReadFunction( _
   ByVal dataVariable As UADataVariable, _
   ByVal valueTypeCode As TypeCode, _
   ByVal readFunction As Func(Of UAAttributeData) _
) As UADataVariable
'Usage
 
Dim dataVariable As UADataVariable
Dim valueTypeCode As TypeCode
Dim readFunction As Func(Of UAAttributeData)
Dim value As UADataVariable
 
value = UADataVariableExtension.ReadFunction(dataVariable, valueTypeCode, readFunction)

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).
readFunction
The read function, i.e. the function that performs the read operation and returns the attribute data 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 dataVariable, internally modified as defined by the method.

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

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.

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.

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

See Also