OPC Studio User's Guide and Reference
ReadMultipleValues Method (_EasyUAClient)
Example 



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OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA.ComTypes Namespace > _EasyUAClient Interface : ReadMultipleValues Method
Array of OpcLabs.EasyOpc.UA.OperationModel.UAReadArguments. Array of argument objects specifying what to read from an OPC-UA server.
Reads values of multiple attributes. Reads values of multiple attributes, using array of argument objects as an input.
Reads values of multiple attributes.
Syntax
'Declaration
 
<ElementsNotNullAttribute()>
<NotNullAttribute()>
Function ReadMultipleValues( _
   ByVal readArgumentsArray As Object _
) As Object()
 
'Usage
 
Dim instance As _EasyUAClient
Dim readArgumentsArray As Object
Dim value() As Object
 
value = instance.ReadMultipleValues(readArgumentsArray)

Parameters

readArgumentsArray
Array of OpcLabs.EasyOpc.UA.OperationModel.UAReadArguments. Array of argument objects specifying what to read from an OPC-UA server.

Return Value

Array of OpcLabs.BaseLib.OperationModel.ValueResult. Returns an array of value objects. Each object contains the actual value of an attribute. The indices of elements in the output array are the same as those in the input array, readArgumentsArray.
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.

Remarks

The status codes of attributes should be 'good'; otherwise, a OpcLabs.BaseLib.OperationModel.ValueResult.Value of that attribute is not valid, and OpcLabs.BaseLib.OperationModel.OperationResult.Exception contains a non-null exception.

The size of the input array will become the size of the output array. The element positions (indices) in the output array are the same as in the input array.

 

This is a multiple-operation method. In a properly written program, it does not throw any exceptions. You should therefore not put try/catch statements or similar constructs around calls to this method. The only exceptions thrown by this method are for usage errors, i.e. when your code violates the usage contract of the method, such as passing in invalid arguments or calling the method when the state of the object does not allow it. Any operation-related errors (i.e. errors that depend on external conditions that your code cannot reliably check) are indicated in the result objects returned by the method. For more information, see Multiple-operation Methods and Do not catch any exceptions with asynchronous or multiple-operation methods.
Example

.NET

.NET

COM

COM

// This example shows how to read the Value attributes of 3 different nodes at once. Using the same method, it is also possible 
// to read multiple attributes of the same node.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

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

namespace UADocExamples._EasyUAClient
{
    partial class ReadMultipleValues
    {
        public static void Main1()
        {
            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 values. By default, the Value attributes of the nodes will be read.
            ValueResult[] valueResultArray = client.ReadMultipleValues(new[]
                {
                    new UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10845"),
                    new UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853"),
                    new UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10855")
                });

            // Display results.
            foreach (ValueResult valueResult in valueResultArray)
            {
                if (valueResult.Succeeded)
                    Console.WriteLine($"Value: {valueResult.Value}");
                else
                    Console.WriteLine($"*** Failure: {valueResult.ErrorMessageBrief}");
            }


            // Example output:
            //
            //Value: 8
            //Value: -8.06803E+21
            //Value: Strawberry Pig Banana Snake Mango Purple Grape Monkey Purple? Blueberry Lemon^            
        }
    }
}
// This example shows how to read the Value attributes of 3 different nodes at once. Using the same method, it is also possible 
// to read multiple attributes of the same node.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

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

namespace UADocExamples._EasyUAClient
{
    partial class ReadMultipleValues
    {
        public static void DataType()
        {
            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 values.
            ValueResult[] valueResultArray = client.ReadMultipleValues(new[]
                {
                    new UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10845", UAAttributeId.DataType),
                    new UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10853", UAAttributeId.DataType),
                    new UAReadArguments(endpointDescriptor, "nsu=http://test.org/UA/Data/ ;i=10855", UAAttributeId.DataType)
                });

            // Display results.
            foreach (ValueResult valueResult in valueResultArray)
            {
                Console.WriteLine();

                if (valueResult.Succeeded)
                {
                    Console.WriteLine($"Value: {valueResult.Value}");
                    var dataTypeId = valueResult.Value as UANodeId;
                    if (!(dataTypeId is null))
                    {
                        Console.WriteLine($"Value.ExpandedText: {dataTypeId.ExpandedText}");
                        Console.WriteLine($"Value.NamespaceUriString: {dataTypeId.NamespaceUriString}");
                        Console.WriteLine($"Value.NamespaceIndex: {dataTypeId.NamespaceIndex}");
                        Console.WriteLine($"Value.NumericIdentifier: {dataTypeId.NumericIdentifier}");
                    }
                }
                else
                    Console.WriteLine($"*** Failure: {valueResult.ErrorMessageBrief}");
            }

            // Example output:
            //
            //Value: SByte
            //Value.ExpandedText: nsu=http://opcfoundation.org/UA/ ;i=2
            //Value.NamespaceUriString: http://opcfoundation.org/UA/
            //Value.NamespaceIndex: 0
            //Value.NumericIdentifier: 2
            //
            //Value: Float
            //Value.ExpandedText: nsu=http://opcfoundation.org/UA/ ;i=10
            //Value.NamespaceUriString: http://opcfoundation.org/UA/
            //Value.NamespaceIndex: 0
            //Value.NumericIdentifier: 10
            //
            //Value: String
            //Value.ExpandedText: nsu=http://opcfoundation.org/UA/ ;i=12
            //Value.NamespaceUriString: http://opcfoundation.org/UA/
            //Value.NamespaceIndex: 0
            //Value.NumericIdentifier: 12
        }
    }
}
// This example shows how to read the Value attributes of 3 different nodes at once. Using the same method, it is also possible 
// to read multiple attributes of the same node.
//
// Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

#include "stdafx.h"    // Includes "QuickOpc.h", and other commonly used files
#include <atlsafe.h>
#include "ReadMultipleValues.h"

namespace _EasyUAClient
{
    void ReadMultipleValues::Main()
    {
        // Initialize the COM library
        CoInitializeEx(NULL, COINIT_MULTITHREADED);
        {
            // Instantiate the client object
            _EasyUAClientPtr ClientPtr(__uuidof(EasyUAClient));

            _UAReadArgumentsPtr ReadArguments1Ptr(_uuidof(UAReadArguments));
            ReadArguments1Ptr->EndpointDescriptor->UrlString = 
                //L"http://opcua.demo-this.com:51211/UA/SampleServer";
                L"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            ReadArguments1Ptr->NodeDescriptor->NodeId->ExpandedText = L"nsu=http://test.org/UA/Data/ ;i=10845";

            _UAReadArgumentsPtr ReadArguments2Ptr(_uuidof(UAReadArguments));
            ReadArguments2Ptr->EndpointDescriptor->UrlString = 
                //L"http://opcua.demo-this.com:51211/UA/SampleServer";
                L"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            ReadArguments2Ptr->NodeDescriptor->NodeId->ExpandedText = L"nsu=http://test.org/UA/Data/ ;i=10853";

            _UAReadArgumentsPtr ReadArguments3Ptr(_uuidof(UAReadArguments));
            ReadArguments3Ptr->EndpointDescriptor->UrlString = 
                //L"http://opcua.demo-this.com:51211/UA/SampleServer";
                L"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer";
            ReadArguments3Ptr->NodeDescriptor->NodeId->ExpandedText = L"nsu=http://test.org/UA/Data/ ;i=10855";

            CComSafeArray<VARIANT> arguments(3);
            arguments.SetAt(0, _variant_t((IDispatch*)ReadArguments1Ptr));
            arguments.SetAt(1, _variant_t((IDispatch*)ReadArguments2Ptr));
            arguments.SetAt(2, _variant_t((IDispatch*)ReadArguments3Ptr));
            CComVariant vArguments(arguments);

            // Obtain values. By default, the Value attributes of the nodes will be read.
            CComSafeArray<VARIANT> results;
            results.Attach(ClientPtr->ReadMultipleValues(&vArguments));
            
            // Display results
            for (int i = results.GetLowerBound(); i <= results.GetUpperBound(); i++)
            {
                _ValueResultPtr ValueResultPtr = results[i];

                _variant_t vString;
                vString.ChangeType(VT_BSTR, &ValueResultPtr->Value);
                _tprintf(_T("Value: %s\n"), (LPCTSTR)CW2CT((_bstr_t)vString));
            }

            // Example output:
            //
            //Value: 8
            //Value: -8.06803E+21
            //Value: Strawberry Pig Banana Snake Mango Purple Grape Monkey Purple? Blueberry Lemon^            
        }
         // Release all interface pointers BEFORE calling CoUninitialize()
        CoUninitialize();
    }
}
// This example shows how to read the DataType attributes of 3 different nodes at
// once. Using the same method, it is also possible to read multiple attributes
// of the same node.
//
// Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

class procedure ReadMultipleValues.DataType;
var
  Client: OpcLabs_EasyOpcUA_TLB._EasyUAClient;
  ReadArguments1, ReadArguments2, ReadArguments3: _UAReadArguments;
  Arguments, Results: OleVariant;
  I: Cardinal;
  Result: _ValueResult;
begin
  // Instantiate the client object
  Client := CoEasyUAClient.Create;

  ReadArguments1 := CoUAReadArguments.Create;
  ReadArguments1.EndpointDescriptor.UrlString := 
    //'http://opcua.demo-this.com:51211/UA/SampleServer';
    //'https://opcua.demo-this.com:51212/UA/SampleServer/';
    'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer';
  ReadArguments1.NodeDescriptor.NodeId.ExpandedText := 'nsu=http://test.org/UA/Data/ ;i=10845';
  ReadArguments1.AttributeId := UAAttributeId_DataType;

  ReadArguments2 := CoUAReadArguments.Create;
  ReadArguments2.EndpointDescriptor.UrlString := 
    //'http://opcua.demo-this.com:51211/UA/SampleServer';
    //'https://opcua.demo-this.com:51212/UA/SampleServer/';
    'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer';
  ReadArguments2.NodeDescriptor.NodeId.ExpandedText := 'nsu=http://test.org/UA/Data/ ;i=10853';
  ReadArguments2.AttributeId := UAAttributeId_DataType;

  ReadArguments3 := CoUAReadArguments.Create;
  ReadArguments3.EndpointDescriptor.UrlString := 
    //'http://opcua.demo-this.com:51211/UA/SampleServer';
    //'https://opcua.demo-this.com:51212/UA/SampleServer/';
    'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer';
  ReadArguments3.NodeDescriptor.NodeId.ExpandedText := 'nsu=http://test.org/UA/Data/ ;i=10855';
  ReadArguments3.AttributeId := UAAttributeId_DataType;

  Arguments := VarArrayCreate([0, 2], varVariant);
  Arguments[0] := ReadArguments1;
  Arguments[1] := ReadArguments2;
  Arguments[2] := ReadArguments3;

  // Obtain values. By default, the Value attributes of the nodes will be read.
  TVarData(Results).VType := varArray or varVariant;
  TVarData(Results).VArray := PVarArray(Client.ReadMultipleValues(Arguments));

  // Display results
  for I := VarArrayLowBound(Results, 1) to VarArrayHighBound(Results, 1) do
  begin
      Result := IInterface(Results[I]) as _ValueResult;
      WriteLn;
      if Result.Succeeded then
      begin
          WriteLn('Value: ', Result.Value);
          WriteLn('Value.ExpandedText: ', Result.Value.ExpandedText);
          WriteLn('Value.NamespaceUriString: ', Result.Value.NamespaceUriString);
          WriteLn('Value.NamespaceIndex: ', Result.Value.NamespaceIndex);
          WriteLn('Value.NumericIdentifier: ', Result.Value.NumericIdentifier);
      end
      else
        WriteLn('results(', I, ') *** Failure: ', Result.ErrorMessageBrief);
  end;
  
  VarClear(Results);
  VarClear(Arguments);

  // Example output:
  //
  //
  //Value: SByte
  //Value.ExpandedText: nsu=http://opcfoundation.org/UA/;i=2
  //Value.NamespaceUriString: http://opcfoundation.org/UA/
  //Value.NamespaceIndex: 0
  //Value.NumericIdentifier: 2
  //
  //Value: Float
  //Value.ExpandedText: nsu=http://opcfoundation.org/UA/;i=10
  //Value.NamespaceUriString: http://opcfoundation.org/UA/
  //Value.NamespaceIndex: 0
  //Value.NumericIdentifier: 10
  //
  //Value: String
  //Value.ExpandedText: nsu=http://opcfoundation.org/UA/;i=12
  //Value.NamespaceUriString: http://opcfoundation.org/UA/
  //Value.NamespaceIndex: 0
  //Value.NumericIdentifier: 12
end;
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