QuickOPC User's Guide and Reference
DAPropertyElement Class
Members 



View with Navigation Tools
OpcLabs.EasyOpcClassicCore Assembly > OpcLabs.EasyOpc.DataAccess.AddressSpace Namespace : DAPropertyElement Class
Contains information gathered about an OPC property.
Object Model
DAPropertyElement ClassVarType ClassVarType ClassDAPropertyId ClassXmlQualifiedName2 ClassDAPropertyId ClassXmlQualifiedName2 Class
Syntax
'Declaration
 
<CLSCompliantAttribute(True)>
<ComDefaultInterfaceAttribute(OpcLabs.EasyOpc.DataAccess.AddressSpace.ComTypes._DAPropertyElement)>
<ComVisibleAttribute(True)>
<GuidAttribute("33FF8F12-EF7B-4C54-9467-579C6ABC3EB0")>
<TypeConverterAttribute(System.ComponentModel.ExpandableObjectConverter)>
<ValueControlAttribute("OpcLabs.BaseLib.Forms.Common.ObjectSerializationControl, OpcLabs.BaseLibForms, Version=5.72.465.1, Culture=neutral, PublicKeyToken=6faddca41dacb409", 
   DefaultReadWrite=False, 
   Export=True, 
   PageId=10001)>
<SerializableAttribute()>
Public NotInheritable Class DAPropertyElement 
   Inherits OpcLabs.BaseLib.Info
   Implements LINQPad.ICustomMemberProvider, OpcLabs.BaseLib.ComTypes._Info, OpcLabs.BaseLib.ComTypes._Object2, OpcLabs.EasyOpc.DataAccess.AddressSpace.ComTypes._DAPropertyElement, System.ICloneable, System.Runtime.Serialization.ISerializable, System.Xml.Serialization.IXmlSerializable 
 
'Usage
 
Dim instance As DAPropertyElement
Remarks
This object is filled in and returned e.g. when you browse the properties of an OPC item.

 

Each OPC item has typically associated a set of OPC properties with it. OPC properties contain additional information related to the item. The OPC specifications define a set of common properties; however, each OPC server is free to implement some more, vendor-specific properties as well.

If you want to retrieve a list of all properties available on a given OPC item, call the BrowseProperties method, passing it the ItemID you are interested in. You will receive back a DAPropertyElementCollection object. Each DAPropertyElement contains information about one OPC property, such as its (numeric) PropertyId, data type, or a readable description. The PropertyId can be later used as an argument in calling methods such as GetPropertyValue.

You can use DAPropertyId.GetName and GetPropertyType methods to obtain the string identifier of the property, or its type. With OPC XML, properties are identified by a XML qualified name, and you will find it in the DAPropertyElement.QualifiedName property.

Constants for specific (well-known) OPC properties are contained in the DAPropertyIds enumeration.

.NET

// This example shows how to enumerate all properties of an OPC item. For each property, it displays its Id and description.

using System;
using OpcLabs.EasyOpc.DataAccess;
using OpcLabs.EasyOpc.DataAccess.AddressSpace;
using OpcLabs.EasyOpc.OperationModel;

namespace DocExamples.DataAccess._EasyDAClient
{
    class BrowseProperties
    {
        public static void Main1()
        {
            // Instantiate the client object.
            var client = new EasyDAClient();
            DAPropertyElementCollection propertyElements;
            try
            {
                propertyElements = client.BrowseProperties("OPCLabs.KitServer.2", "Simulation.Random");
            }
            catch (OpcException opcException)
            {
                Console.WriteLine("*** Failure: {0}", opcException.GetBaseException().Message);
                return;
            }

            foreach (DAPropertyElement propertyElement in propertyElements)
                Console.WriteLine($"PropertyElements(\"{propertyElement.PropertyId.NumericalValue}\").Description: {propertyElement.Description}");
        }


        // Example output:
        //
        //PropertyElements("15008").Description: Visible
        //PropertyElements("5").Description: Item Access Rights
        //PropertyElements("2").Description: Item Value
        //PropertyElements("7").Description: Item EU Type
        //PropertyElements("15001").Description: Item Name
        //PropertyElements("4").Description: Item Timestamp
        //PropertyElements("1").Description: Item Canonical Data Type
        //PropertyElements("103").Description: Low EU
        //PropertyElements("15009").Description: Addable
        //PropertyElements("6").Description: Server Scan Rate
        //PropertyElements("15000").Description: Item ID
        //PropertyElements("3").Description: Item Quality
    }
}

COM

// This example shows how to enumerate all properties of an OPC item. For each property, it displays its Id and description.

class procedure BrowseProperties.Main;
var
  Client: OpcLabs_EasyOpcClassic_TLB._EasyDAClient;
  Count: Cardinal;
  Element: OleVariant;
  ServerDescriptor: _ServerDescriptor;
  NodeDescriptor: _DANodeDescriptor;
  PropertyElement: _DAPropertyElement;
  PropertyElementEnumerator: IEnumVariant;
  PropertyElements: _DAPropertyElementCollection;
begin
  ServerDescriptor := CoServerDescriptor.Create;
  ServerDescriptor.ServerClass := 'OPCLabs.KitServer.2';

  NodeDescriptor := CoDANodeDescriptor.Create;
  NodeDescriptor.ItemId := 'Simulation.Random';

  // Instantiate the client object
  Client := CoEasyDAClient.Create;

  try
    PropertyElements := Client.BrowseProperties(
      ServerDescriptor,
      NodeDescriptor);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;

  PropertyElementEnumerator := PropertyElements.GetEnumerator;
  while (PropertyElementEnumerator.Next(1, Element, Count) = S_OK) do
  begin
    PropertyElement := IUnknown(Element) as _DAPropertyElement;
    WriteLn('PropertyElements("', PropertyElement.PropertyId.NumericalValue, '").Description: ', PropertyElement.Description);
  end;
end;

 

 

 

Inheritance Hierarchy

System.Object
   OpcLabs.BaseLib.Object2
      OpcLabs.BaseLib.Info
         OpcLabs.EasyOpc.DataAccess.AddressSpace.DAPropertyElement

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