'Declaration
 
<NotNullAttribute()>
Function ReadItem( _
   ByVal machineName As String, _
   ByVal serverClass As String, _
   ByVal itemId As String _
) As DAVtq

'Usage
 
Dim instance As _EasyDAClient
Dim machineName As String
Dim serverClass As String
Dim itemId As String
Dim value As DAVtq
 
value = instance.ReadItem(machineName, serverClass, itemId)

[NotNull()]
DAVtq ReadItem( 
   string machineName,
   string serverClass,
   string itemId
)

[NotNull()]
DAVtq^ ReadItem( 
   String^ machineName,
   String^ serverClass,
   String^ itemId
) 

Parameters

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 can be null (Nothing in Visual Basic).

serverClass

Contains ProgID of the OPC server to read from.

The value of this parameter can be null (Nothing in Visual Basic).

itemId

Contains OPC item identifier.

The value of this parameter can be null (Nothing in Visual Basic).

Return Value

This member or type is for use from COM. It is not meant to be used from .NET or Python. Refer to the corresponding .NET member or type instead, if you are developing in .NET or Python.

COM

// This example shows how to read a single item, and display its value, timestamp and quality.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

var Client = new ActiveXObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient");
var VTQ = Client.ReadItem("", "OPCLabs.KitServer.2", "Simulation.Random");
WScript.Echo("VTQ.ToString(): " + VTQ.ToString());

// This example shows how to read a single item, and display its value, timestamp and quality.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in Object Pascal (Delphi) on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-OP .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

class procedure ReadItem.Main;
var
  Client: OpcLabs_EasyOpcClassic_TLB._EasyDAClient;
  Vtq: _DAVtq;
begin
  // Instantiate the client object
  Client := CoEasyDAClient.Create;

  try
    Vtq := Client.ReadItem('', 'OPCLabs.KitServer.2', 'Simulation.Random');
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;

  // Display results
  WriteLn('Vtq: ', Vtq.ToString);
end;

// This example shows how to read a single item, and display its value, timestamp and quality.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in PHP on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PHP .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

$Client = new COM("OpcLabs.EasyOpc.DataAccess.EasyDAClient");

try
{
    $Vtq = $Client->ReadItem("", "OPCLabs.KitServer.2", "Simulation.Random");
}
catch (com_exception $e)
{
    printf("*** Failure: %s\n", $e->getMessage());
    Exit();
}

printf("Vtq: %s\n", $Vtq);

// This example shows how to read a single item, and display its value, timestamp and quality.

mle_outputtext.Text = ""

// Instantiate the client object
OLEObject client
client = CREATE OLEObject
client.ConnectToNewObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")

// Obtain value/timestamp/quality
OLEObject vtq
TRY
    vtq = client.ReadItem("", "OPCLabs.KitServer.2", "Demo.Ramp")
CATCH (OLERuntimeError oleRuntimeError)
    mle_outputtext.Text = mle_outputtext.Text + "*** Failure: " + oleRuntimeError.Description + "~r~n"
    RETURN
END TRY

// Display results
mle_outputtext.Text = mle_outputtext.Text + "Vtq: " + vtq.DisplayString + "~r~n"

REM This example shows how to read a single item, and display its value, timestamp and quality.
REM
REM Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
REM OPC client and subscriber examples in Visual Basic on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VB .
REM Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
REM a commercial license in order to use Online Forums, and we reply to every post.

Private Sub ReadItem_Main_Command_Click()
    OutputText = ""
    
    ' Instantiate the client object
    Dim client As New EasyDAClient

    On Error Resume Next
    Dim vtq As DAVtq
    Set vtq = client.ReadItem("", "OPCLabs.KitServer.2", "Simulation.Random")
    If Err.Number <> 0 Then
        OutputText = OutputText & "*** Failure: " & Err.Source & ": " & Err.Description & vbCrLf
        Exit Sub
    End If
    On Error GoTo 0

    ' Display results
    OutputText = OutputText & "Vtq: " & vtq & vbCrLf
End Sub

Rem This example shows how to read a single item, and display its value, timestamp and quality.
Rem
Rem Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
Rem OPC client and subscriber examples in VBScript on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBScript .
Rem Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
Rem a commercial license in order to use Online Forums, and we reply to every post.

Option Explicit

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")
On Error Resume Next
Dim Vtq: Set Vtq = Client.ReadItem("", "OPCLabs.KitServer.2", "Simulation.Random")
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0
WScript.Echo "Vtq: " & Vtq

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows