DeviceSource Property (DAReadParameters)

Read parameters that specify the device data source.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<NotNullAttribute()>
Public Shared ReadOnly Property DeviceSource As DAReadParameters

'Usage
 
Dim value As DAReadParameters
 
value = DAReadParameters.DeviceSource

[NotNull()]
public static DAReadParameters DeviceSource {get;}

[NotNull()]
public:
static property DAReadParameters^ DeviceSource {
   DAReadParameters^ get();
}

Property Value

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

Remarks

OPC reads will be fulfilled from the device by the OPC server.

This method or property does not throw any exceptions, aside from execution exceptions such as System.Threading.ThreadAbortException or System.OutOfMemoryException.

Example

CSharp
VB.NET
VBScript
Python

// This example shows how to read 4 items from the device, and display their values, timestamps and qualities.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// 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.

using System;
using System.Diagnostics;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    partial class ReadMultipleItems
    {
        public static void DeviceSource()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            // DADataSource enumeration:
            // Selects the data source for OPC reads (from device, from OPC cache, or dynamically determined).
            // The data source (memory, OPC cache or OPC device) selection will be based on the desired value age and
            // current status of data received from the server.

            DAVtqResult[] vtqResults = client.ReadMultipleItems(
                new []
                    {
                        new DAReadItemArguments("OPCLabs.KitServer.2", "Simulation.Random", DADataSource.Device),
                        new DAReadItemArguments("OPCLabs.KitServer.2", "Trends.Ramp (1 min)", DADataSource.Device),
                        new DAReadItemArguments("OPCLabs.KitServer.2", "Trends.Sine (1 min)", DADataSource.Device),
                        new DAReadItemArguments("OPCLabs.KitServer.2", "Simulation.Register_I4", DADataSource.Device)
                    });

            for (int i = 0; i < vtqResults.Length; i++)
            {
                Debug.Assert(vtqResults[i] != null);

                if (vtqResults[i].Succeeded)
                    Console.WriteLine("vtqResults[{0}].Vtq: {1}", i, vtqResults[i].Vtq);
                else
                    Console.WriteLine("vtqResults[{0}] *** Failure: {1}", i, vtqResults[i].ErrorMessageBrief);
            }
        }


        // Example output:
        //
        //vtqResults[0].Vtq: 0.00125125888851588 { System.Double} @2020-04-10T12:44:16.250; GoodNonspecific(192)
        //vtqResults[1].Vtq: 0.270812898874283 {System.Double} @2020-04-10T12:44:16.248; GoodNonspecific(192)
        //vtqResults[2].Vtq: 0.991434340167834 {System.Double} @2020-04-10T12:44:16.250; GoodNonspecific(192)
        //vtqResults[3].Vtq: 0 {System.Int32} @1601-01-01T00:00:00.000; GoodNonspecific(192)
    }
}

' This example shows how to read 4 items from the device, and display their values, timestamps and qualities.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess._EasyDAClient
    Partial Friend Class ReadMultipleItems
        Public Shared Sub DeviceSource()
            ' Instantiate the client object.
            Dim client = New EasyDAClient()

            ' DADataSource enumeration
            ' Selects the data source for OPC reads (from device, from OPC cache, or dynamically determined).
            ' The data source (memory, OPC cache or OPC device) selection will be based on the desired value age and
            ' current status of data received from the server.

            Dim vtqResults() As DAVtqResult = client.ReadMultipleItems(New DAReadItemArguments() {
                New DAReadItemArguments("OPCLabs.KitServer.2", "Simulation.Random", DADataSource.Device),
                New DAReadItemArguments("OPCLabs.KitServer.2", "Trends.Ramp (1 min)", DADataSource.Device),
                New DAReadItemArguments("OPCLabs.KitServer.2", "Trends.Sine (1 min)", DADataSource.Device),
                New DAReadItemArguments("OPCLabs.KitServer.2", "Simulation.Register_I4", DADataSource.Device)
            })

            For i = 0 To vtqResults.Length - 1
                Debug.Assert(vtqResults(i) IsNot Nothing)

                If vtqResults(i).Succeeded Then
                    Console.WriteLine("vtqResults[{0}].Vtq: {1}", i, vtqResults(i).Vtq)
                Else
                    Console.WriteLine("vtqResults[{0}] *** Failure: {1}", i, vtqResults(i).ErrorMessageBrief)
                End If
            Next i
        End Sub

        ' Example output
        '
        'vtqResults[0].Vtq: 0.00125125888851588 { System.Double} @2020-04-10T12:44:16.250; GoodNonspecific(192)
        'vtqResults[1].Vtq: 0.270812898874283 {System.Double} @2020-04-10T12:44:16.248; GoodNonspecific(192)
        'vtqResults[2].Vtq: 0.991434340167834 {System.Double} @2020-04-10T12:44:16.250; GoodNonspecific(192)
        'vtqResults[3].Vtq: 0 {System.Int32} @1601-01-01T00:00:00.000; GoodNonspecific(192)
    End Class
End Namespace

Rem This example shows how to read 4 items from the device, and display their values, timestamps and qualities.
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

' Selects the data source for OPC reads (from device, from OPC cache, or dynamically determined).
' The data source (memory, OPC cache or OPC device) selection will be based on the desired value age and current status of 
' data received from the server.
Const DADataSource_ByValueAge = 0
' OPC reads will be fulfilled from the cache in the OPC server.
Const DADataSource_Cache = 1
' OPC reads will be fulfilled from the device by the OPC server.
Const DADataSource_Device = 2

Dim ReadItemArguments1: Set ReadItemArguments1 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments1.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments1.ItemDescriptor.ItemID = "Simulation.Random"
ReadItemArguments1.ReadParameters.DataSource = DADataSource_Device  ' read will be from device

Dim ReadItemArguments2: Set ReadItemArguments2 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments2.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments2.ItemDescriptor.ItemID = "Trends.Ramp (1 min)"
ReadItemArguments2.ReadParameters.DataSource = DADataSource_Device  ' read will be from device

Dim ReadItemArguments3: Set ReadItemArguments3 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments3.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments3.ItemDescriptor.ItemID = "Trends.Sine (1 min)"
ReadItemArguments3.ReadParameters.DataSource = DADataSource_Device  ' read will be from device

Dim ReadItemArguments4: Set ReadItemArguments4 = CreateObject("OpcLabs.EasyOpc.DataAccess.OperationModel.DAReadItemArguments")
ReadItemArguments4.ServerDescriptor.ServerClass = "OPCLabs.KitServer.2"
ReadItemArguments4.ItemDescriptor.ItemID = "Simulation.Register_I4"
ReadItemArguments4.ReadParameters.DataSource = DADataSource_Device  ' read will be from device

Dim arguments(3)
Set arguments(0) = ReadItemArguments1
Set arguments(1) = ReadItemArguments2
Set arguments(2) = ReadItemArguments3
Set arguments(3) = ReadItemArguments4

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.DataAccess.EasyDAClient")

Dim results: results = Client.ReadMultipleItems(arguments)

Dim i: For i = LBound(results) To UBound(results)
    Dim VtqResult: Set VtqResult = results(i)
    If VtqResult.Succeeded Then
        WScript.Echo "results(" & i & ").Vtq.ToString(): " & VtqResult.Vtq.ToString()
    Else
        WScript.Echo "results(" & i & ") *** Failure: " & VtqResult.ErrorMessageBrief
    End If
Next

# This example shows how to read 4 items from the device, and display their values, timestamps and qualities.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# 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.
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from OpcLabs.EasyOpc import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.DataAccess.OperationModel import *
from OpcLabs.EasyOpc.OperationModel import *


# Instantiate the client object.
client = EasyDAClient()

# DADataSource enumeration:
# Selects the data source for OPC reads (from device, from OPC cache, or dynamically determined).
# The data source (memory, OPC cache or OPC device) selection is based on the desired value age and
# current status of data received from the server.

#
vtqResultArray = client.ReadMultipleItems([
    DAReadItemArguments(ServerDescriptor('OPCLabs.KitServer.2'), DAItemDescriptor('Simulation.Random'), DAReadParameters(DADataSource.Device)),
    DAReadItemArguments(ServerDescriptor('OPCLabs.KitServer.2'), DAItemDescriptor('Trends.Ramp (1 min)'), DAReadParameters(DADataSource.Device)),
    DAReadItemArguments(ServerDescriptor('OPCLabs.KitServer.2'), DAItemDescriptor('Trends.Sine (1 min)'), DAReadParameters(DADataSource.Device)),
    DAReadItemArguments(ServerDescriptor('OPCLabs.KitServer.2'), DAItemDescriptor('Simulation.Register_I4'), DAReadParameters(DADataSource.Device)),
    ])

for i, vtqResult in enumerate(vtqResultArray):
    assert vtqResult is not None
    if vtqResult.Succeeded:
        print('vtqResultArray[', i, '].Vtq: ', vtqResult.Vtq, sep='')
    else:
        print('vtqResultArray[', i, '] *** Failure: ', vtqResult.ErrorMessageBrief, sep='')

CSharp
VB.NET
Python

// This example shows how to read 4 items from the device, and display their values, timestamps and qualities.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// 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.

using System;
using System.Diagnostics;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.OperationModel;

namespace DocExamples.DataAccess.Xml
{
    partial class ReadMultipleItems
    {
        public static void DeviceSourceXml()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            // DADataSource enumeration:
            // Selects the data source for OPC reads (from device, from OPC cache, or dynamically determined).
            // The data source (memory, OPC cache or OPC device) selection will be based on the desired value age and
            // current status of data received from the server.

            DAVtqResult[] vtqResults = client.ReadMultipleItems(
                new []
                    {
                        new DAReadItemArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", "Dynamic/Analog Types/Double", DADataSource.Device),
                        new DAReadItemArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", "Dynamic/Analog Types/Double[]", DADataSource.Device),
                        new DAReadItemArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", "Dynamic/Analog Types/Int", DADataSource.Device),
                        new DAReadItemArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", "Static/Analog Types/Int", DADataSource.Device)
                    });

            for (int i = 0; i < vtqResults.Length; i++)
            {
                Debug.Assert(vtqResults[i] != null);

                if (vtqResults[i].Succeeded)
                    Console.WriteLine("vtqResults[{0}].Vtq: {1}", i, vtqResults[i].Vtq);
                else
                    Console.WriteLine("vtqResults[{0}] *** Failure: {1}", i, vtqResults[i].ErrorMessageBrief);
            }
        }


        // Example output:
        //
        //vtqResults[0].Vtq: 100 {Double} @2024-01-01T14:31:03.232; GoodNonspecific (192)
        //vtqResults[1].Vtq: [3] {1000, 1000, 1000} {Double[]} @2024-01-01T14:31:03.232; GoodNonspecific (192)
        //vtqResults[2].Vtq: 700 {Int32} @2024-01-01T14:31:03.232; GoodNonspecific (192)
        //vtqResults[3].Vtq: 0 {Int32} @2024-01-01T14:31:03.232; GoodNonspecific (192)

    }
}

' This example shows how to read 4 items from the device, and display their values, timestamps and qualities.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' 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.

Imports OpcLabs.EasyOpc.DataAccess
Imports OpcLabs.EasyOpc.DataAccess.OperationModel

Namespace DataAccess.Xml
    Partial Friend Class ReadMultipleItems
        Public Shared Sub DeviceSourceXml()
            ' Instantiate the client object.
            Dim client = New EasyDAClient()

            ' DADataSource enumeration
            ' Selects the data source for OPC reads (from device, from OPC cache, or dynamically determined).
            ' The data source (memory, OPC cache or OPC device) selection will be based on the desired value age and
            ' current status of data received from the server.

            Dim vtqResults() As DAVtqResult = client.ReadMultipleItems(New DAReadItemArguments() {
                New DAReadItemArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", "Dynamic/Analog Types/Double", DADataSource.Device),
                New DAReadItemArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", "Dynamic/Analog Types/Double[]", DADataSource.Device),
                New DAReadItemArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", "Dynamic/Analog Types/Int", DADataSource.Device),
                New DAReadItemArguments("http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx", "Static/Analog Types/Int", DADataSource.Device)
            })

            For i = 0 To vtqResults.Length - 1
                Debug.Assert(vtqResults(i) IsNot Nothing)

                If vtqResults(i).Succeeded Then
                    Console.WriteLine("vtqResults[{0}].Vtq: {1}", i, vtqResults(i).Vtq)
                Else
                    Console.WriteLine("vtqResults[{0}] *** Failure: {1}", i, vtqResults(i).ErrorMessageBrief)
                End If
            Next i
        End Sub

        ' Example output
        '
        'vtqResults[0].Vtq: 100 {Double} @2024-01-01T14:31:03.232; GoodNonspecific (192)
        'vtqResults[1].Vtq: [3] {1000, 1000, 1000} {Double[]} @2024-01-01T14:31:03.232; GoodNonspecific (192)
        'vtqResults[2].Vtq: 700 {Int32} @2024-01-01T14:31:03.232; GoodNonspecific (192)
        'vtqResults[3].Vtq: 0 {Int32} @2024-01-01T14:31:03.232; GoodNonspecific (192)
    End Class
End Namespace

# This example shows how to read 4 items from the device, and display their values, timestamps and qualities.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# 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.
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from OpcLabs.EasyOpc import *
from OpcLabs.EasyOpc.DataAccess import *
from OpcLabs.EasyOpc.DataAccess.OperationModel import *


# Instantiate the client object.
client = EasyDAClient()

# DADataSource enumeration:
# Selects the data source for OPC reads (from device, from OPC cache, or dynamically determined).
# The data source (memory, OPC cache or OPC device) selection will be based on the desired value age and
# current status of data received from the server.

vtqResults = client.ReadMultipleItems(
    [
        DAReadItemArguments(ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx'), DAItemDescriptor('Dynamic/Analog Types/Double'), DAReadParameters(DADataSource.Device)),
        DAReadItemArguments(ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx'), DAItemDescriptor('Dynamic/Analog Types/Double[]'), DAReadParameters(DADataSource.Device)),
        DAReadItemArguments(ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx'), DAItemDescriptor('Dynamic/Analog Types/Int'), DAReadParameters(DADataSource.Device)),
        DAReadItemArguments(ServerDescriptor('http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx'), DAItemDescriptor('Static/Analog Types/Int'), DAReadParameters(DADataSource.Device))
    ])

for i, vtqResult in enumerate(vtqResults):
    assert vtqResult is not None
    if vtqResult.Succeeded:
        print('vtqResults[', i, '].Vtq: ', vtqResult.Vtq, sep='')
    else:
        print('vtqResults[', i, '] *** Failure: ', vtqResult.ErrorMessageBrief, sep='')

# Example output:
#
#vtqResults[0].Vtq: 100 {Double} @2024-01-01T14:31:03.232; GoodNonspecific (192)
#vtqResults[1].Vtq: [3] {1000, 1000, 1000} {Double[]} @2024-01-01T14:31:03.232; GoodNonspecific (192)
#vtqResults[2].Vtq: 700 {Int32} @2024-01-01T14:31:03.232; GoodNonspecific (192)
#vtqResults[3].Vtq: 0 {Int32} @2024-01-01T14:31:03.232; GoodNonspecific (192)

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

DAReadParameters Class
DAReadParameters Members

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