ReadItemValueArrayOfDateTime(IEasyDAClient,ServerDescriptor,DANodeDescriptor,DAReadParameters) Method

Reads a value of named OPC item, and converts it to an array of System.DateTime. The value is requested from the OPC server using a corresponding data type.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ExtensionAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function ReadItemValueArrayOfDateTime( _
   ByVal client As IEasyDAClient, _
   ByVal serverDescriptor As ServerDescriptor, _
   ByVal nodeDescriptor As DANodeDescriptor, _
   ByVal readParameters As DAReadParameters _
) As Date()

'Usage
 
Dim client As IEasyDAClient
Dim serverDescriptor As ServerDescriptor
Dim nodeDescriptor As DANodeDescriptor
Dim readParameters As DAReadParameters
Dim value() As Date
 
value = IEasyDAClientExtension2.ReadItemValueArrayOfDateTime(client, serverDescriptor, nodeDescriptor, readParameters)

[Extension()]
[NotNull()]
public static DateTime[] ReadItemValueArrayOfDateTime( 
   IEasyDAClient client,
   ServerDescriptor serverDescriptor,
   DANodeDescriptor nodeDescriptor,
   DAReadParameters readParameters
)

[Extension()]
[NotNull()]
public:
static array<DateTime>^ ReadItemValueArrayOfDateTime( 
   IEasyDAClient^ client,
   ServerDescriptor^ serverDescriptor,
   DANodeDescriptor^ nodeDescriptor,
   DAReadParameters^ readParameters
)

Parameters

client

The client object that will perform the operation.

This is typically the OpcLabs.EasyOpc.DataAccess.EasyDAClient object.

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

serverDescriptor

The OPC server involved in the operation.

Because the OpcLabs.EasyOpc.ServerDescriptor has an implicit conversion from System.Guid, System.String and OpcLabs.EasyOpc.ServerElement, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a GUID (representing the CLSID of the server), a string (representing the so-called OPC server descriptor string, such as a ProgID or the URL of the server), or a OpcLabs.EasyOpc.ServerElement object (result from OPC browsing), in place of this parameter, and the corresponding OPC server descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.EasyOpc.ServerDescriptor.FromGuid, OpcLabs.EasyOpc.ServerDescriptor.FromString or OpcLabs.EasyOpc.ServerDescriptor.FromServerElement static method instead.

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

nodeDescriptor

The descriptor of the OPC node involved in the operation.

Because the OpcLabs.EasyOpc.DataAccess.DANodeDescriptor has an implicit conversion from System.String and OpcLabs.EasyOpc.DataAccess.AddressSpace.DANodeElement, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a string (representing the qualified name of the node), or a OpcLabs.EasyOpc.DataAccess.AddressSpace.DANodeElement object (result from OPC browsing), in place of this parameter, and the corresponding OPC DA node descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the FromString or FromDANodeElement static method instead.

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

readParameters

The read parameters (such as data source or value age).

Because the OpcLabs.EasyOpc.DataAccess.DAReadParameters has an implicit conversion from System.Int32 and OpcLabs.EasyOpc.DataAccess.DADataSource, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use an integer (representing the value age in milliseconds), or an element of the OpcLabs.EasyOpc.DataAccess.DADataSource enumeration in place of this parameter, and the corresponding OPC DA read parameters object will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the DAReadParameters Constructor(Int32) or DAReadParameters Constructor(DADataSource) constructor instead.

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

Return Value

Returns a value of the OPC item, converted to a type indicated by the method name.

This method never returns null (Nothing in Visual Basic).

Exceptions

Exception Description

Exception	Description
System.ArgumentNullException	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.
OpcLabs.EasyOpc.OperationModel.OpcException	The OPC "Classic" (or OPC XML-DA) operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause. This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

System.ArgumentNullException

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.

OpcLabs.EasyOpc.OperationModel.OpcException

The OPC "Classic" (or OPC XML-DA) operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause.

This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

Remarks

Using implicit conversions, you can pass an item ID in place of node descriptor. You can also pass a value age in place of read parameters

The server(s) can be local or can be remotely accessed via DCOM.

This is an extension method (info: C#, VB.NET). In languages that have support for extensions methods (such as C# and VB.NET), you can use the extension method as if it were a regular method on the object that is its first parameter. In other languages (such as with Python.NET), you will call the extension as a static method, and pass it the object on which it acts as its first parameter.

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

IEasyDAClientExtension2 Class
IEasyDAClientExtension2 Members
Overload List

Documentation Home, Send Feedback. Resources: Knowledge Base, Product Downloads. Technical support: Online Forums, FAQ.

Missing some example? Ask us for it on our Online Forums! You do not have to own a commercial license in order to use Online Forums, and we reply to every post.