OPC Studio User's Guide and Reference
Elements Property (SequenceData)
Example 



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OpcLabs.BaseLib Assembly > OpcLabs.BaseLib.DataTypeModel Namespace > SequenceData Class : Elements Property
The elements of the sequence data.
Syntax
'Declaration
 
<ElementsCanBeNullAttribute()>
Public Property Elements As GenericDataCollection
 
'Usage
 
Dim instance As SequenceData
Dim value As GenericDataCollection
 
instance.Elements = value
 
value = instance.Elements
Remarks

Relation of SequenceData and its constituents is shown on the following picture:

.

Example

.NET

COM

.NET

COM

// Shows how to write complex data with OPC UA Complex Data plug-in.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

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

namespace UADocExamples.ComplexData._EasyUAClient
{
    class WriteValue
    {
        public static void Main1()
        {
            // Define which server and node we will work with.
            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/"
            UANodeDescriptor nodeDescriptor =
                "nsu=http://test.org/UA/Data/ ;i=10239"; // [ObjectsFolder]/Data.Static.Scalar.StructureValue

            // Instantiate the client object.
            var client = new EasyUAClient();

            // Read a node which returns complex data. 
            // We know that this node returns complex data, so we can type cast to UAGenericObject.
            Console.WriteLine("Reading...");
            UAGenericObject genericObject;
            try
            {
                genericObject = (UAGenericObject)client.ReadValue(endpointDescriptor, nodeDescriptor);
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }


            // Modify the data read.
            // This node returns one of the two data types, randomly (this is not common, usually the type is fixed). The
            // data types are sub-types of one common type which the data type of the node. We therefore use the data type 
            // ID in the returned UAGenericObject to detect which data type has been returned.

            // For processing the internals of the data, refer to examples for GenericData and DataType classes.
            // We know how the data is structured, and have hard-coded a logic that modifies certain values inside. It is
            // also possible to discover the structure of the data type in the program, and write generic clients that can 
            // cope with any kind of complex data.
            //
            // Note that the code below is not fully robust - it will throw an exception if the data is not as expected.
            Console.WriteLine("Modifying...");
            Console.WriteLine(genericObject.DataTypeId);
            if (genericObject.DataTypeId.NodeDescriptor.Match("nsu=http://test.org/UA/Data/ ;i=9440"))  // ScalarValueDataType
            {
                // Negate the byte in the "ByteValue" field.
                var structuredData = (StructuredData)genericObject.GenericData;
                var byteValue = (PrimitiveData)structuredData.FieldData["ByteValue"];
                byteValue.Value = (Byte)~((Byte)byteValue.Value);
                Console.WriteLine(byteValue.Value);
            }
            else if (genericObject.DataTypeId.NodeDescriptor.Match("nsu=http://test.org/UA/Data/ ;i=9669")) // ArrayValueDataType
            {
                // Negate bytes at indexes 0 and 1 of the array in the "ByteValue" field.
                var structuredData = (StructuredData)genericObject.GenericData;
                var byteValue = (SequenceData)structuredData.FieldData["ByteValue"];
                var element0 = (PrimitiveData)byteValue.Elements[0];
                var element1 = (PrimitiveData)byteValue.Elements[1];
                element0.Value = (Byte)~((Byte)element0.Value);
                element1.Value = (Byte)~((Byte)element1.Value);
                Console.WriteLine(element0.Value);
                Console.WriteLine(element1.Value);
            }


            // Write the modified complex data back to the node.
            // The data type ID in the UAGenericObject is borrowed without change from what we have read, so that the server
            // knows which data type we are writing. The data type ID not necessary if writing precisely the same data type
            // as the node has (not a subtype).
            Console.WriteLine("Writing...");
            try
            {
                client.WriteValue(endpointDescriptor, nodeDescriptor, genericObject);
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
            }
        }
    }
}
// Shows how to write complex data with OPC UA Complex Data plug-in.
//
// Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

class procedure WriteValue.Main;
var
  ArrayValueDataType: _UANodeDescriptor;
  ByteValue: _PrimitiveData;
  ByteValue2: _SequenceData;
  Client: _EasyUAClient;
  Element0, Element1: _PrimitiveData;
  EndpointDescriptor: string;
  GenericObject: _UAGenericObject;
  NodeDescriptor: string;
  ScalarValueDataType: _UANodeDescriptor;
  StructuredData: _StructuredData;
begin
  // Define which server and node we will work with.
  EndpointDescriptor := 
    //'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';
  NodeDescriptor := 'nsu=http://test.org/UA/Data/ ;i=10239';  // [ObjectsFolder]/Data.Static.Scalar.StructureValue

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

  // Read a node which returns complex data.
  // We know that this node returns complex data, so we can type cast to UAGenericObject.
  WriteLn('Reading...');

  try
    GenericObject := _UAGenericObject(IUnknown(Client.ReadValue(EndpointDescriptor, NodeDescriptor)));
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;

  // Modify the data read.
  // This node returns one of the two data types, randomly (this is not common, usually the type is fixed). The
  // data types are sub-types of one common type which the data type of the node. We therefore use the data type
  // ID in the returned UAGenericObject to detect which data type has been returned.

  // For processing the internals of the data, refer to examples for GenericData and DataType classes.
  // We know how the data is structured, and have hard-coded a logic that modifies certain values inside. It is
  // also possible to discover the structure of the data type in the program, and write generic clients that can
  // cope with any kind of complex data.
  //
  // Note that the code below is not fully robust - it will throw an exception if the data is not as expected.

  WriteLn('Modifying...');
  WriteLn(GenericObject.DataTypeId.ToString);
  ScalarValueDataType := CoUANodeDescriptor.Create;
  ScalarValueDataType.NodeId.ExpandedText := 'nsu=http://test.org/UA/Data/ ;i=9440'; // ScalarValueDataType
  if GenericObject.DataTypeId.NodeDescriptor.Match(ScalarValueDataType) then
  begin
    // Negate the byte in the "ByteValue" field.
    StructuredData := IUnknown(GenericObject.GenericData) as _StructuredData;
    ByteValue := IUnknown(StructuredData.FieldData['ByteValue']) as _PrimitiveData;
    ByteValue.Value := Byte(not (Byte(byteValue.Value)));
    WriteLn(ByteValue.Value);
  end
  else
  begin
    ArrayValueDataType := CoUANodeDescriptor.Create;
    ArrayValueDataType.NodeId.ExpandedText := 'nsu=http://test.org/UA/Data/ ;i=9669'; // ArrayValueDataType
    if GenericObject.DataTypeId.Nodedescriptor.Match(ArrayValueDataType) then
    begin
      // Negate bytes at indexes 0 and 1 of the array in the "ByteValue" field.
      StructuredData := IUnknown(GenericObject.GenericData) as _StructuredData;
      ByteValue2 := IUnknown(StructuredData.FieldData['ByteValue']) as _SequenceData;
      Element0 := IUnknown(ByteValue2.Elements[0]) as _PrimitiveData;
      Element1 := IUnknown(ByteValue2.Elements[1]) as _PrimitiveData;
      Element0.Value := Byte(not (Byte(element0.Value)));
      Element1.Value := Byte(not (Byte(element1.Value)));
      WriteLn(Element0.Value);
      WriteLn(Element1.Value);
    end;
  end;

  // Write the modified complex data back to the node.
  // The data type ID in the UAGenericObject is borrowed without change from what we have read, so that the server
  // knows which data type we are writing. The data type ID not necessary if writing precisely the same data type
  // as the node has (not a subtype).
  WriteLn('Writing...');
  try
    Client.WriteValue(EndpointDescriptor, NodeDescriptor, GenericObject);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;

end;
// Shows how to process generic data type, displaying some of its properties, recursively.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

using System;
using System.Collections.Generic;
using OpcLabs.BaseLib.DataTypeModel;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.ComplexData;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples.ComplexData._GenericData
{
    class DataTypeKind1
    {
        public static void Main1()
        {
            // Define which server and node we will work with.
            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/"
            UANodeDescriptor nodeDescriptor =
                "nsu=http://test.org/UA/Data/ ;i=10239"; // [ObjectsFolder]/Data.Static.Scalar.StructureValue

            // Instantiate the client object.
            var client = new EasyUAClient();

            // Read a node. We know that this node returns complex data, so we can type cast to UAGenericObject.
            UAGenericObject genericObject;
            try
            {
                genericObject = (UAGenericObject)client.ReadValue(endpointDescriptor, nodeDescriptor);
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }

            // Process the generic data type. We will inspect some of its properties, and dump them.
            ProcessGenericData(genericObject.GenericData, maximumDepth: 3);
        }
        

        // Process the generic data type. Its structure can sometimes be quite deep, therefore we are limiting the depth
        // of the recursion using maximumDepth.
        public static void ProcessGenericData(GenericData genericData, int maximumDepth)
        {
            if (maximumDepth == 0)
                return;

            Console.WriteLine();
            Console.WriteLine("genericData.DataType: {0}", genericData.DataType);

            switch (genericData.DataTypeKind)
            {
                case DataTypeKind.Enumeration:
                    Console.WriteLine("The generic data is an enumeration.");
                    var enumerationData = (EnumerationData) genericData;
                    Console.WriteLine("Its value is {0}.", enumerationData.Value);
                    // There is also a ValueName that you can inspect (if known).
                    break;

                case DataTypeKind.Opaque:
                    Console.WriteLine("The generic data is opaque.");
                    var opaqueData = (OpaqueData) genericData;
                    Console.WriteLine("Its size is {0} bits.", opaqueData.SizeInBits);
                    Console.WriteLine("The data bytes are {0}.", BitConverter.ToString(opaqueData.ByteArray));
                    // Use the Value property (a BitArray) if you need to access the value bit by bit.
                    break;

                case DataTypeKind.Primitive:
                    Console.WriteLine("The generic data is primitive.");
                    var primitiveData = (PrimitiveData) genericData;
                    Console.WriteLine("Its value is \"{0}\".", primitiveData.Value);
                    break;

                case DataTypeKind.Sequence:
                    Console.WriteLine("The generic data is a sequence.");
                    var sequenceData = (SequenceData) genericData;
                    Console.WriteLine("It has {0} elements.", sequenceData.Elements.Count);
                    Console.WriteLine("A dump of the elements follows.");
                    foreach (GenericData element in sequenceData.Elements)
                        ProcessGenericData(element, maximumDepth - 1);
                    break;

                case DataTypeKind.Structured:
                    Console.WriteLine("The generic data is structured.");
                    var structuredData = (StructuredData) genericData;
                    Console.WriteLine("It has {0} field data members.", structuredData.FieldData.Count);
                    Console.WriteLine("The names of the fields are: {0}.",
                        String.Join(", ", structuredData.FieldData.Keys));

                    Console.WriteLine("A dump of each of the fields follows.");
                    foreach (KeyValuePair<string, GenericData> pair in structuredData.FieldData)
                    {
                        Console.WriteLine();
                        Console.WriteLine("Field name: {0}", pair.Key);
                        ProcessGenericData(pair.Value, maximumDepth - 1);
                    }
                    break;

                case DataTypeKind.Union:
                    Console.WriteLine("The generic data is a union.");
                    var unionData = (UnionData)genericData;
                    Console.WriteLine("The name of current field is: {0}", unionData.FieldName);
                    Console.WriteLine("Current field value is: {0}", unionData.FieldValue);
                    break;
            }
        }
    }
}
// Shows how to process generic data type, displaying some of its properties, recursively
//
// Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

class procedure DataTypeKind1.Main;
var
  Client: _EasyUAClient;
  EndpointDescriptor: string;
  GenericObject: _UAGenericObject;
  NodeDescriptor: string;
begin
  EndpointDescriptor := 
    //'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';
  NodeDescriptor := 'nsu=http://test.org/UA/Data/ ;i=10239';  // [ObjectsFolder]/Data.Static.Scalar.StructureValue

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

  // Read a node. We know that this node returns complex data, so we can type cast to UAGenericObject.

  try
    GenericObject := _UAGenericObject(IUnknown(Client.ReadValue(EndpointDescriptor, NodeDescriptor)));
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;

  // Process the generic data type. We will inspect some of its properties, and dump them.
  ProcessGenericData(GenericObject.GenericData, 2);
end;

Function VariantToBytes(Const Value: OleVariant): TBytes;
Var
  Size: Integer;
  pData: Pointer;
Begin
  Size := Succ(VarArrayHighBound(Value, 1) - VarArrayLowBound(Value, 1));
  SetLength(Result, Size);
  pData := VarArrayLock(Value);
  Try
    Move(pData^, Pointer(Result)^, Size);
  Finally
    VarArrayUnlock(Value);
  End;
End;

class procedure DatatypeKind1.ProcessGenericData(GenericData: OpcLabs_BaseLib_TLB._GenericData; MaximumDepth: Cardinal);
var
  ByteArray: OleVariant;
  Count: Cardinal;
  Element: OleVariant;
  ElementEnumerator: IEnumVARIANT;
  EnumerationData: _EnumerationData;
  First: boolean;
  Keys: string;
  OpaqueData: _OpaqueData;
  PrimitiveData: _PrimitiveData;
  SequenceData: _SequenceData;
  StructuredData: _StructuredData;
  Value: OpcLabs_BaseLib_TLB._GenericData;
begin
  if MaximumDepth = 0 then
    Exit;

  WriteLn;
  WriteLn('genericData.DataType: ', GenericData.DataType.ToString);

  case GenericData.DataTypeKind of
    DataTypeKind_Enumeration:
      begin
        WriteLn('The generic data is an enumeration.');
        EnumerationData := GenericData as _EnumerationData;
        WriteLn(Format('Its value is %s.', [EnumerationData.Value.ToString]));
        // There is also a ValueName that you can inspect (if known).
      end;
    DataTypeKind_Opaque:
      begin
        WriteLn('The generic data is opaque.');
        OpaqueData := GenericData as _OpaqueData;
        WriteLn(Format('Its size is %d bits.', [OpaqueData.SizeInBits]));
        TVarData(ByteArray).VType := varArray;
        TVarData(ByteArray).VArray := PVarArray(OpaqueData.ByteArray);
        WriteLn(Format('The data bytes are %s.', [TEncoding.ANSI.GetString(VariantToBytes(ByteArray))]));
        // Use the Value property (a BitArray) if you need to access the value bit by bit.
      end;
    DataTypeKind_Primitive:
      begin
        WriteLn('The generic data is primitive.');
        PrimitiveData := GenericData as _PrimitiveData;
        WriteLn(Format('Its value is "%s".', [PrimitiveData.Value]));
      end;
    DataTypeKind_Sequence:
      begin
        WriteLn('The generic data is a sequence.');
        SequenceData := GenericData as _SequenceData;
        WriteLn(Format('It has %s elements.', [SequenceData.Elements.Count.ToString]));
        WriteLn('A dump of the elements follows.');
        ElementEnumerator := SequenceData.Elements.GetEnumerator;
        while (ElementEnumerator.Next(1, Element, Count) = S_OK) do
        begin
          ProcessGenericData(IUnknown(Element) as OpcLabs_BaseLib_TLB._GenericData, MaximumDepth - 1);
        end;
      end;
    DataTypeKind_Structured:
      begin
        WriteLn('The generic data is structured.');
        StructuredData := GenericData as _StructuredData;
        WriteLn(Format('It has %s field data members.', [StructuredData.FieldData.Count.ToString]));
        ElementEnumerator := StructuredData.FieldData.GetEnumerator;
        Keys := '';
        First := True;
        while (ElementEnumerator.Next(1, Element, Count) = S_OK) do
        begin
          if First then
            First := False
          else
            Keys := Keys + ', ';
          Keys := Keys + Element.Key;
        end;
        WriteLn(Format('The names of the fields are: %s.', [Keys]));

        WriteLn('A dump of each of the fields follows.');
        ElementEnumerator := StructuredData.FieldData.GetEnumerator;
        while (ElementEnumerator.Next(1, Element, Count) = S_OK) do
        begin
          WriteLn;
          WriteLn(Format('Field name: %s', [Element.Key]));
          Value := IUnknown(Element.Value) as OpcLabs_BaseLib_TLB._GenericData;
          ProcessGenericData(Value, MaximumDepth - 1);
        end;
      end;
  end;

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