FromDevice Property (UAReadParameters)

Read parameters that specify reading from the device (data source), and a default encoding.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<DebuggerBrowsableAttribute(DebuggerBrowsableState.Never)>
<NotNullAttribute()>
Public Shared ReadOnly Property FromDevice As UAReadParameters

'Usage
 
Dim value As UAReadParameters
 
value = UAReadParameters.FromDevice

[DebuggerBrowsable(DebuggerBrowsableState.Never)]
[NotNull()]
public static UAReadParameters FromDevice {get;}

[DebuggerBrowsable(DebuggerBrowsableState.Never)]
[NotNull()]
public:
static property UAReadParameters^ FromDevice {
   UAReadParameters^ get();
}

Remarks

This set of parameters corresponds to specifying 0 to the maxAge parameter in the OPC UA Read Service request.

Example

.NET

CSharp
Python
VB.NET

// This example shows how to read data from the device (data source) and display a value, timestamps, and status code.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._EasyUAClient
{
    partial class Read
    {
        public static void FromDevice()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            // or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            // or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            // Instantiate the client object
            var client = new EasyUAClient();

            // Obtain attribute data. By default, the Value attribute of a node will be read.
            // The parameters specify reading from the device (data source), which may be slow but provides the very latest
            // data.
            UAAttributeData attributeData;
            try
            {
                attributeData = client.Read(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", 
                    UAReadParameters.FromDevice);
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }

            // Display results
            Console.WriteLine("Value: {0}", attributeData.Value);
            Console.WriteLine("ServerTimestamp: {0}", attributeData.ServerTimestamp);
            Console.WriteLine("SourceTimestamp: {0}", attributeData.SourceTimestamp);
            Console.WriteLine("StatusCode: {0}", attributeData.StatusCode);

            // Example output:
            //
            //Value: -2.230064E-31
            //ServerTimestamp: 11/6/2011 1:34:30 PM
            //SourceTimestamp: 11/6/2011 1:34:30 PM
            //StatusCode: Good
        }
    }
}

# This example shows how to read data from the device (data source) and display a value, timestamps, and status code.
#
# 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 .
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

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


# Instantiate the client object.
client = EasyUAClient()

# Obtain attribute data. By default, the Value attribute of a node will be read.
# The parameters specify reading from the device (data source), which may be slow but provides the very latest
# data.
try:
    attributeData = IEasyUAClientExtension.Read(client,
        UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer'),
        UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10853'),
        UAReadParameters.FromDevice)
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

# Display results.
print('Value: ', attributeData.Value)
print('ServerTimestamp: ', attributeData.ServerTimestamp)
print('SourceTimestamp: ', attributeData.SourceTimestamp)
print('StatusCode: ', attributeData.StatusCode)

' This example shows how to read data from the device (data source) and display a value, timestamps, and status code.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _EasyUAClient
    Partial Friend Class Read
        Public Shared Sub FromDevice()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
            ' or "http://opcua.demo-this.com:51211/UA/SampleServer" (currently not supported)
            ' or "https://opcua.demo-this.com:51212/UA/SampleServer/"

            ' Instantiate the client object
            Dim client = New EasyUAClient()

            ' Obtain attribute data. By default, the Value attribute of a node will be read.
            ' The parameters specify reading from the device (data source), which may be slow but provides the very latest
            ' data.
            Dim attributeData As UAAttributeData
            Try
                attributeData = client.Read(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853",
                    UAReadParameters.FromDevice)
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            ' Display results
            Console.WriteLine("Value: {0}", attributeData.Value)
            Console.WriteLine("ServerTimestamp: {0}", attributeData.ServerTimestamp)
            Console.WriteLine("SourceTimestamp: {0}", attributeData.SourceTimestamp)
            Console.WriteLine("StatusCode: {0}", attributeData.StatusCode)

            ' Example output:
            '
            'Value: -2.230064E-31
            'ServerTimestamp: 11/6/2011 1:34:30 PM
            'SourceTimestamp: 11/6/2011 1:34:30 PM
            'StatusCode: Good
        End Sub
    End Class
End Namespace

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

UAReadParameters Class
UAReadParameters Members
DeviceMaximumAge Field
FromCache Property
MaximumAge Property

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