QuerySourceConditions Method (

Finds out event conditions associated with the specified source name. Uses server descriptor for specifying the OPC server.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<NotNullAttribute()>
Function QuerySourceConditions( _
   ByVal serverDescriptor As Object, _
   ByVal sourceNodeDescriptor As Object _
) As AEConditionElementCollection

'Usage
 
Dim instance As _EasyAEClient
Dim serverDescriptor As Object
Dim sourceNodeDescriptor As Object
Dim value As AEConditionElementCollection
 
value = instance.QuerySourceConditions(serverDescriptor, sourceNodeDescriptor)

[NotNull()]
AEConditionElementCollection QuerySourceConditions( 
   object serverDescriptor,
   object sourceNodeDescriptor
)

[NotNull()]
AEConditionElementCollection^ QuerySourceConditions( 
   Object^ serverDescriptor,
   Object^ sourceNodeDescriptor
)

Parameters

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).

sourceNodeDescriptor

A source node descriptor, usually expressed as qualified source name. Only the conditions associated with this source are returned.

Because the OpcLabs.EasyOpc.AlarmsAndEvents.AENodeDescriptor has an implicit conversion from System.String and OpcLabs.EasyOpc.AlarmsAndEvents.AddressSpace.AENodeElement, 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.AlarmsAndEvents.AddressSpace.AENodeElement object (result from OPC browsing), in place of this parameter, and the corresponding OPC A&E node descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.EasyOpc.AlarmsAndEvents.AENodeDescriptor.FromString or OpcLabs.EasyOpc.AlarmsAndEvents.AENodeDescriptor.FromAENodeElement static method instead.

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

Return Value

A collection of condition elements, one element for each condition of the given source.

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

The individual elements of the returned value are never 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

This member or type is for use from COM. It is not meant to be used from .NET or Python. Refer to the corresponding .NET member or type instead, if you are developing in .NET or Python.

Example

COM

VBScript

Rem This example shows how to enumerate all event conditions associated with the specified event source.
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

Dim ServerDescriptor: Set ServerDescriptor = CreateObject("OpcLabs.EasyOpc.ServerDescriptor")
ServerDescriptor.ServerClass = "OPCLabs.KitEventServer.2"

Dim SourceDescriptor: Set SourceDescriptor = CreateObject("OpcLabs.EasyOpc.AlarmsAndEvents.AENodeDescriptor")
SourceDescriptor.QualifiedName = "Simulation.ConditionState1"

Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.AlarmsAndEvents.EasyAEClient")
On Error Resume Next
Dim ConditionElements: Set ConditionElements = Client.QuerySourceConditions(ServerDescriptor, SourceDescriptor)
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0

Dim ConditionElement: For Each ConditionElement In ConditionElements
    WScript.Echo "ConditionElements(" & ConditionElement.Name & "): " & (UBound(ConditionElement.SubconditionNames) + 1) & " subcondition(s)"
Next

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

_EasyAEClient Interface
_EasyAEClient Members

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