QuickOPC User's Guide and Reference
ReadMultipleItemValues(IEasyDAClient,DAReadItemArguments[]) Method
Example 



OpcLabs.EasyOpcClassic Assembly > OpcLabs.EasyOpc.DataAccess Namespace > IEasyDAClientExtension Class > ReadMultipleItemValues Method : ReadMultipleItemValues(IEasyDAClient,DAReadItemArguments[]) Method
The client object that will perform the operation.
Array of arguments, one element per each OPC item involved in the operation.
Reads named items from an OPC server or OPC servers. Only the item values are returned (qualities and timestamps are not returned). Reads multiple named item values from a single OPC server, using array of argument objects as an input.
Syntax
'Declaration
 

<ExtensionAttribute()>
<ElementsNotNullAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function ReadMultipleItemValues( _
   ByVal client As IEasyDAClient, _
   ByVal argumentsArray() As DAReadItemArguments _
) As ValueResult()
'Usage
 

Dim client As IEasyDAClient
Dim argumentsArray() As DAReadItemArguments
Dim value() As ValueResult
 
value = IEasyDAClientExtension.ReadMultipleItemValues(client, argumentsArray)
[Extension()]
[ElementsNotNull()]
[NotNull()]
public static ValueResult[] ReadMultipleItemValues( 
   IEasyDAClient client,
   DAReadItemArguments[] argumentsArray
)
[Extension()]
[ElementsNotNull()]
[NotNull()]
public:
static array<ValueResult^>^ ReadMultipleItemValues( 
   IEasyDAClient^ client,
   array<DAReadItemArguments^>^ argumentsArray
)

Parameters

client
The client object that will perform the operation.
argumentsArray
Array of arguments, one element per each OPC item involved in the operation.

Return Value

The function returns an array of OpcLabs.BaseLib.OperationModel.ValueResult objects. The indices of elements in the output array are the same as those in the input array, argumentsArray.
Exceptions
ExceptionDescription
System.ArgumentNullExceptionA null reference (Nothing in Visual Basic) is passed to a method that does not accept it as a valid argument.
Remarks

The servers can be local or can be remotely accessed via DCOM. Optionally, an access path can be specified or a specific data type can be requested.

The ReadMultipleItemValues method requires that the quality is "good" for each item. The function performs all individual operations in parallel, but only returns after all individual operations are completed (or their timeouts elapse).

This method does not throw an exception in case of OPC operation failures. Instead, the eventual exception related to each item is returned in Exception property of each returned OpcLabs.EasyOpc.DataAccess.OperationModel.DAVtqResult element.

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.
Example
// This example shows how to read values of 4 items at once, and display them.

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

namespace DocExamples.DataAccess._EasyDAClient
{
    class ReadMultipleItemValues
    {
        public static void Main1()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();

            ValueResult[] valueResults = client.ReadMultipleItemValues("OPCLabs.KitServer.2",
                new DAItemDescriptor[]
                {
                    "Simulation.Random", "Trends.Ramp (1 min)", "Trends.Sine (1 min)", "Simulation.Register_I4"
                });

            for (int i = 0; i < valueResults.Length; i++)
            {
                ValueResult valueResult = valueResults[i];
                Debug.Assert(!(valueResult is null));

                if (valueResult.Succeeded)
                    Console.WriteLine($"valueResults({i}).Value: {valueResult.Value}");
                else
                    Console.WriteLine($"valueResults({i}) *** Failure: {valueResult.ErrorMessageBrief}");
            }
        }


        // Example output:
        //
        //valueResults(0).Value: 0.00125125888851588
        //valueResults(1).Value: 0.732510924339294
        //valueResults(2).Value: -0.993968485238202
        //valueResults(3).Value: 0
    }
}
# This example shows how to read values of 4 items at once, and display them.

#requires -Version 5.1
using namespace OpcLabs.EasyOpc.DataAccess

# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Assemblies/net47/OpcLabs.EasyOpcClassic.dll"

# Instantiate the client object.
$client = New-Object EasyDAClient

$valueResults = [IEasyDAClientExtension]::ReadMultipleItemValues($client, 
    "OPCLabs.KitServer.2", @(
        (New-Object DAItemDescriptor("Simulation.Random")),
        (New-Object DAItemDescriptor("Trends.Ramp (1 min)")),
        (New-Object DAItemDescriptor("Trends.Sine (1 min)")),
        (New-Object DAItemDescriptor("Simulation.Register_I4"))
        ))

for ($i = 0; $i -lt $valueResults.Length; $i++) {
    $valueResult = $valueResults[$i]
    if ($valueResult.Succeeded) {
        Write-Host "valueResults($($i)).Value: $($valueResult.Value)"
    }
    else {
        Write-Host "valueResults($($i)) *** Failure: $($valueResult.ErrorMessageBrief)"
    }
}


# Example output:
#
#valueResults(0).Value: 0.00125125888851588
#valueResults(1).Value: 0.732510924339294
#valueResults(2).Value: -0.993968485238202
#valueResults(3).Value: 0
Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2012, Windows Server 2016; .NET Core, .NET 5, .NET 6: Linux, macOS, Microsoft Windows

See Also

Reference

IEasyDAClientExtension Class
IEasyDAClientExtension Members
Overload List

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