OPC Studio User's Guide and Reference
GetPropertyValueSingle(IEasyDAClient,String,String,String,DAPropertyId) Method



OpcLabs.EasyOpcClassicCore Assembly > OpcLabs.EasyOpc.DataAccess.Extensions Namespace > IEasyDAClientExtension2 Class > GetPropertyValueSingle Method : GetPropertyValueSingle(IEasyDAClient,String,String,String,DAPropertyId) Method
The client object that will perform the operation.

This is typically the OpcLabs.EasyOpc.DataAccess.EasyDAClient object.

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

Name of the machine. Determines the computer on which the OPC server is located. It may be an empty string, in which case the OPC server is assumed to exist on the local computer or at the computer specified for it by DCOM configuration.

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).

Contains ProgID of the OPC server to read from.

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

The Item ID of the OPC item involved in the operation.

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

The Property ID of the OPC property being obtained

Because the OpcLabs.EasyOpc.DataAccess.DAPropertyId has an implicit conversion from System.Int64 and OpcLabs.EasyOpc.DataAccess.DAPropertyIds, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a long integer (representing the numerical value of the access rights), or an element of the OpcLabs.EasyOpc.DataAccess.DAPropertyIds enumeration in place of this parameter, and the corresponding Property Id specification will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the DAPropertyId Constructor(Int64) or DAPropertyId Constructor(DAPropertyIds) constructor instead.

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

Gets a value of OPC property, using individual parameters specifying the OPC server, and OPC Item ID, and converts it to System.Single.
Syntax
'Declaration
 
<ExtensionAttribute()>
Public Overloads Shared Function GetPropertyValueSingle( _
   ByVal client As IEasyDAClient, _
   ByVal machineName As String, _
   ByVal serverClass As String, _
   ByVal itemId As String, _
   ByVal propertyId As DAPropertyId _
) As Single
'Usage
 
Dim client As IEasyDAClient
Dim machineName As String
Dim serverClass As String
Dim itemId As String
Dim propertyId As DAPropertyId
Dim value As Single
 
value = IEasyDAClientExtension2.GetPropertyValueSingle(client, machineName, serverClass, itemId, propertyId)

Parameters

client
The client object that will perform the operation.

This is typically the OpcLabs.EasyOpc.DataAccess.EasyDAClient object.

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

machineName
Name of the machine. Determines the computer on which the OPC server is located. It may be an empty string, in which case the OPC server is assumed to exist on the local computer or at the computer specified for it by DCOM configuration.

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 to read from.

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

itemId
The Item ID of the OPC item involved in the operation.

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

propertyId
The Property ID of the OPC property being obtained

Because the OpcLabs.EasyOpc.DataAccess.DAPropertyId has an implicit conversion from System.Int64 and OpcLabs.EasyOpc.DataAccess.DAPropertyIds, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a long integer (representing the numerical value of the access rights), or an element of the OpcLabs.EasyOpc.DataAccess.DAPropertyIds enumeration in place of this parameter, and the corresponding Property Id specification will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the DAPropertyId Constructor(Int64) or DAPropertyId Constructor(DAPropertyIds) constructor instead.

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

Return Value

If successful, the function returns the actual value of the OPC property requested, converted to a type indicated by the method name.
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 OPC "Classic" (or OPC XML-DA) operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause.

This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

Remarks

The server(s) can be local or can be remotely accessed via DCOM.

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