QuickOPC User's Guide and Reference
DataType Property (_DataField)
Example 



OpcLabs.BaseLib Assembly > OpcLabs.BaseLib.DataTypeModel.ComTypes Namespace > _DataField Interface : DataType Property
The data type of the contents of the field.
Syntax
'Declaration
 
<CanBeNullAttribute()>
Property DataType As DataType
'Usage
 
Dim instance As _DataField
Dim value As DataType
 
instance.DataType = value
 
value = instance.DataType
[CanBeNull()]
DataType DataType {get; set;}
[CanBeNull()]
property DataType^ DataType {
   DataType^ get();
   void set (    DataType^ value);
}
Remarks

If the data type is a null reference, or is incomplete, the data field is incomplete (the IsComplete property equals to false).

Example

.NET

COM

// Shows how to process a data type, displaying some of its properties, recursively.

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

namespace UADocExamples.ComplexData._DataType
{
    class Kind
    {
        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;
            }
            // The data type is in the GenericData.DataType property of the UAGenericObject.
            DataType dataType = genericObject.GenericData.DataType;

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

        // Process the data type. It can be recursive in itself, so if you do not know the data type you are dealing with, 
        // it is recommended to make safeguards against infinite looping or recursion - here, the maximumDepth.
        public static void ProcessDataType(DataType dataType, int maximumDepth)
        {
            if (maximumDepth == 0)
                return;

            Console.WriteLine();
            Console.WriteLine("dataType.Name: {0}", dataType.Name);

            switch (dataType.Kind)
            {
                case DataTypeKind.Enumeration:
                    Console.WriteLine("The data type is an enumeration.");
                    var enumerationDataType = (EnumerationDataType) dataType;
                    Console.WriteLine("It has {0} enumeration members.", enumerationDataType.EnumerationMembers.Count);
                    Console.WriteLine("The names of the enumeration members are: {0}.",
                        String.Join(", ", enumerationDataType.EnumerationMembers.Select(member => member.Name)));
                    // Here you can process the members, or inspect SizeInBits etc.
                    break;

                case DataTypeKind.Opaque:
                    Console.WriteLine("The data type is opaque.");
                    var opaqueDataType = (OpaqueDataType) dataType;
                    Console.WriteLine("Its size is {0} bits.", opaqueDataType.SizeInBits);
                    // There isn't much more you can learn about an opaque data type (well, it may have Description and 
                    // other common members). It is, after all, opaque...
                    break;

                case DataTypeKind.Primitive:
                    Console.WriteLine("The data type is primitive.");
                    var primitiveDataType = (PrimitiveDataType) dataType;
                    Console.WriteLine("Its .NET value type is \"{0}\".", primitiveDataType.ValueType);
                    // There isn't much more you can learn about the primitive data type.
                    break;

                case DataTypeKind.Sequence:
                    Console.WriteLine("The data type is a sequence.");
                    var sequenceDataType = (SequenceDataType) dataType;
                    Console.WriteLine("Its length is {0} (-1 means that the length can vary).", sequenceDataType.Length);

                    Console.WriteLine("A dump of the element data type follows.");
                    ProcessDataType(sequenceDataType.ElementDataType, maximumDepth - 1);
                    break;

                case DataTypeKind.Structured:
                    Console.WriteLine("The data type is structured.");
                    var structuredDataType = (StructuredDataType) dataType;
                    Console.WriteLine("It has {0} data fields.", structuredDataType.DataFields.Count);
                    Console.WriteLine("The names of the data fields are: {0}.",
                        String.Join(", ", structuredDataType.DataFields.Select(field => field.Name)));

                    Console.WriteLine("A dump of each of the data fields follows.");
                    foreach (DataField dataField in structuredDataType.DataFields)
                    {
                        Console.WriteLine();
                        Console.WriteLine("dataField.Name: {0}", dataField.Name);
                        // Note that every data field also has properties like IsLength, IsOptional, IsSwitch which might 
                        // be of interest, but we are not dumping them here.
                        ProcessDataType(dataField.DataType, maximumDepth - 1);
                    }
                    break;

                case DataTypeKind.Union:
                    Console.WriteLine("The data type is union.");
                    var unionDataType = (UnionDataType)dataType;
                    Console.WriteLine("It has {0} data fields.", unionDataType.DataFields.Count);
                    Console.WriteLine("The names of the data fields are: {0}.",
                        String.Join(", ", unionDataType.DataFields.Select(field => field.Name)));
                    break;
            }
        }
    }
}
# Shows how to process a data type, displaying some of its properties, recursively.

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from System import *
from OpcLabs.BaseLib.DataTypeModel import *
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.OperationModel import *


def processDataType(dataType, maximumDepth):
    if maximumDepth == 0:
        print('* Reached maximum depth *')
        return

    print()
    print('dataType.Name: ', dataType.Name, sep='')

    if dataType.Kind == DataTypeKind.Enumeration:
        print('The data type is an enumeration.')
        enumerationDataType = dataType
        print('It has ', enumerationDataType.EnumerationMembers.Count, ' enumeration members.', sep='')
        print('The names of the enumeration members are: ', end='')
        for i, member in enumerate(enumerationDataType.EnumerationMembers):
            if i != 0:
                print(', ', end='')
            print(member.Name, end='')
        print('.')
        # Here you can process the members, or inspect SizeInBits etc.

    elif dataType.Kind == DataTypeKind.Opaque:
        print('The data type is opaque.')
        opaqueDataType = dataType
        print('Its size is ', opaqueDataType.SizeInBits, ' bits.', sep='')
        # There isn't much more you can learn about an opaque data type (well, it may have Description and
        # other common members). It is, after all, opaque...

    elif dataType.Kind == DataTypeKind.Primitive:
        print('The data type is primitive.')
        primitiveDataType = dataType
        print('Its .NET value type is "', primitiveDataType.ValueType, '".', sep='')
        # There isn't much more you can learn about the primitive data type.

    elif dataType.Kind == DataTypeKind.Sequence:
        print('The data type is a sequence.')
        sequenceDataType = dataType
        print('Its length is ', sequenceDataType.Length, ' (-1 means that the length can vary).', sep='')

        print('A dump of the element data type follows.')
        processDataType(sequenceDataType.ElementDataType, maximumDepth - 1)

    elif dataType.Kind == DataTypeKind.Structured:
        print('The data type is structured.')
        structuredDataType = dataType
        print('It has ', structuredDataType.DataFields.Count, ' data fields.', sep='')
        print('The names of the data fields are: ', end='')
        for i, field in enumerate(structuredDataType.DataFields):
            if i != 0:
                print(', ', end='')
            print(field.Name, end='')
        print('.')

        print('A dump of each of the data fields follows.')
        for dataField in structuredDataType.DataFields:
            print()
            print('dataField.Name: ', dataField.Name, sep='')
            # Note that every data field also has properties like IsLength, IsOptional, IsSwitch which might
            # be of interest, but we are not dumping them here.
            processDataType(dataField.DataType, maximumDepth - 1)

    elif dataType.Kind == DataTypeKind.Union:
        print('The data type is union.')
        unionDataType = dataType
        print('It has ', unionDataType.DataFields.Count, ' data fields.', sep='')
        print('The names of the data fields are: ', end='')
        for i, field in enumerate(unionDataType.DataFields):
            if i != 0:
                print(', ', end='')
            print(field.Name, end='')
        print('.')


# Define which server and node we will work with.
endpointDescriptor = UAEndpointDescriptor('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/'

# [ObjectsFolder]/Data.Static.Scalar.StructureValue
nodeDescriptor = UANodeDescriptor('nsu=http://test.org/UA/Data/ ;i=10239')

# Instantiate the client object.
client = EasyUAClient()

# Read a node. We know that this node returns complex data, so we can type cast to UAGenericObject.
try:
    print('Reading...')
    genericObject = IEasyUAClientExtension.ReadValue(client, endpointDescriptor, nodeDescriptor)
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()
print('Reading successful.')
# The data type is in the GenericData.DataType property of the UAGenericObject.
dataType = genericObject.GenericData.DataType

# Process the data type. We will inspect some of its properties, and dump them.
processDataType(dataType, 3)

print()
print('Finished.')
' Shows how to process a data type, displaying some of its properties, recursively.

Imports System
Imports System.Linq
Imports OpcLabs.BaseLib.DataTypeModel
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.ComplexData
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace ComplexData._DataType

    Friend Class Kind

        Public Shared Sub Main1()

            ' Define which server we will work with.
            Dim endpointDescriptor As UAEndpointDescriptor =
                    "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/"

            ' Define which node we will work with.
            Dim nodeDescriptor As UANodeDescriptor = _
                "nsu=http://test.org/UA/Data/ ;i=10239"  ' [ObjectsFolder]/Data.Static.Scalar.StructureValue

            ' Instantiate the client object.
            Dim client = New EasyUAClient

            ' Read a node. We know that this node returns complex data, so we can type cast to UAGenericObject.
            Dim genericObject As UAGenericObject
            Try
                genericObject = CType(client.ReadValue(endpointDescriptor, nodeDescriptor), UAGenericObject)
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try
            ' The data type is in the GenericData.DataType property of the UAGenericObject.

            Dim dataType As DataType = genericObject.GenericData.DataType

            ' Process the data type. We will inspect some of its properties, and dump them.
            ProcessDataType(dataType, maximumDepth:=2)
        End Sub


        ' Process the data type. It can be recursive in itself, so if you do not know the data type you are dealing with, 
        ' it is recommended to make safeguards against infinite looping or recursion - here, the maximumDepth.
        Public Shared Sub ProcessDataType(dataType As DataType, ByVal maximumDepth As Integer)
            If (maximumDepth = 0) Then
                Return
            End If

            Console.WriteLine()
            Console.WriteLine("dataType.Name: {0}", dataType.Name)

            Select Case (dataType.Kind)
                Case DataTypeKind.Enumeration
                    Console.WriteLine("The data type is an enumeration.")
                    Dim enumerationDataType = CType(dataType, EnumerationDataType)
                    Console.WriteLine("It has {0} enumeration members.", enumerationDataType.EnumerationMembers.Count)
                    Console.WriteLine("The names of the enumeration members are: {0}.", _
                                      String.Join(", ", enumerationDataType.EnumerationMembers.Select(Function(member) member.Name)))
                    ' Here you can process the members, or inspect SizeInBits etc.

                Case DataTypeKind.Opaque
                    Console.WriteLine("The data type is opaque.")
                    Dim opaqueDataType = CType(dataType, OpaqueDataType)
                    Console.WriteLine("Its size is {0} bits.", opaqueDataType.SizeInBits)
                    ' There isn't much more you can learn about an opaque data type (well, it may have Description and 
                    ' other common members). It is, after all, opaque...

                Case DataTypeKind.Primitive
                    Console.WriteLine("The data type is primitive.")
                    Dim primitiveDataType = CType(dataType, PrimitiveDataType)
                    Console.WriteLine("Its .NET value type is ""{0}"".", primitiveDataType.ValueType)
                    ' There isn't much more you can learn about the primitive data type.

                Case DataTypeKind.Sequence
                    Console.WriteLine("The data type is a sequence.")
                    Dim sequenceDataType = CType(dataType, SequenceDataType)
                    Console.WriteLine("Its length is {0} (-1 means that the length can vary).", sequenceDataType.Length)
                    Console.WriteLine("A dump of the element data type follows.")
                    ProcessDataType(sequenceDataType.ElementDataType, (maximumDepth - 1))

                Case DataTypeKind.Structured
                    Console.WriteLine("The data type is structured.")
                    Dim structuredDataType = CType(dataType, StructuredDataType)
                    Console.WriteLine("It has {0} data fields.", structuredDataType.DataFields.Count)
                    Console.WriteLine("The names of the data fields are: {0}.", _
                                      String.Join(", ", structuredDataType.DataFields.Select(Function(field) field.Name)))
                    Console.WriteLine("A dump of each of the data fields follows.")

                    For Each dataField As DataField In structuredDataType.DataFields
                        Console.WriteLine()
                        Console.WriteLine("dataField.Name: {0}", dataField.Name)
                        ' Note that every data field also has properties like IsLength, IsOptional, IsSwitch which might 
                        ' be of interest but we are not dumping them here.
                        ProcessDataType(dataField.DataType, (maximumDepth - 1))
                    Next

                Case DataTypeKind.Union
                    Console.WriteLine("The data type is union.")
                    Dim unionDataType = CType(dataType, UnionDataType)
                    Console.WriteLine("It has {0} data fields.", unionDataType.DataFields.Count)
                    Console.WriteLine("The names of the data fields are: {0}.",
                                      String.Join(", ", unionDataType.DataFields.Select(Function(field) field.Name)))

            End Select

        End Sub
    End Class
End Namespace
// Shows how to process a data type, displaying some of its properties, recursively.

class procedure Kind.Main;
var
  Client: _EasyUAClient;
  DataType: OpcLabs_BaseLib_TLB._DataType;
  EndpointDescriptor: string;
  GenericObject: _UAGenericObject;
  NodeDescriptor: string;
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. We know that this node returns complex data, so we can type cast to UAGenericObject.

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

  // The data type is in the GenericData.DataType property of the UAGenericObject.
  DataType := genericObject.GenericData.DataType;

  // Process the data type. We will inspect some of its properties, and dump them.
  ProcessDataType(DataType, 2);
end;

// Process the data type. It can be recursive in itself, so if you do not know the data type you are dealing with,
// it is recommended to make safeguards against infinite looping or recursion - here, the maximumDepth.
class procedure Kind.ProcessDataType(DataType: OpcLabs_BaseLib_TLB._DataType; MaximumDepth: Cardinal);
var
  Count: Cardinal;
  DataField: _DataField;
  Element: OleVariant;
  ElementEnumerator: IEnumVARIANT;
  EnumerationMember: _EnumerationMember;
  EnumerationDataType: _EnumerationDataType;
  FieldNames: string;
  First: boolean;
  MemberNames: string;
  OpaqueDataType: _OpaqueDataType;
  PrimitiveDataType: _PrimitiveDataType;
  SequenceDataType: _SequenceDataType;
  StructuredDataType: _StructuredDataType;
  TypeName: WideString;
begin
  if MaximumDepth = 0 then
    Exit;

  WriteLn;
  WriteLn('dataType.Name: ', DataType.Name);

  case DataType.Kind of
    DataTypeKind_Enumeration:
      begin
        WriteLn('The data type is an enumeration.');
        EnumerationDataType := DataType as _EnumerationDataType;
        WriteLn(Format('It has %s enumeration members.', [EnumerationDataType.EnumerationMembers.Count]));
        ElementEnumerator := EnumerationDataType.EnumerationMembers.GetEnumerator;
        MemberNames := '';
        First := True;
        while (ElementEnumerator.Next(1, Element, Count) = S_OK) do
        begin
          EnumerationMember := IUnknown(Element) as _EnumerationMember;
          if First then
            First := False
          else
            MemberNames := MemberNames + ', ';
          MemberNames := MemberNames + EnumerationMember.Name;
        end;
        WriteLn(Format('The names of the enumeration members are: %s.', [MemberNames]));
        // Here you can process the members, or inspect SizeInBits etc.
      end;
    DataTypeKind_Opaque:
      begin
        WriteLn('The data type is opaque.');
        OpaqueDataType := DataType as _OpaqueDataType;
        WriteLn(Format('Its size is %s bits.', [OpaqueDataType.SizeInBits]));
        // There isn't much more you can learn about an opaque data type (well, it may have Description and
        // other common members). It is, after all, opaque...
      end;
    DataTypeKind_Primitive:
      begin
        WriteLn('The data type is primitive.');
        PrimitiveDataType := DataType as _PrimitiveDataType;
        PrimitiveDataType.ValueType.Get_ToString(TypeName);
        WriteLn(Format('Its .NET value type is "%s".', [TypeName]));
        // There isn't much more you can learn about the primitive data type.
      end;
    DataTypeKind_Sequence:
      begin
        WriteLn('The data type is a sequence.');
        SequenceDataType := DataType as _SequenceDataType;
        WriteLn(Format('Its length is %s (-1 means that the length can vary).', [SequenceDataType.Length.ToString]));
        WriteLn('A dump of the element data type follows.');
        ProcessDataType(SequenceDataType.ElementDataType, MaximumDepth - 1);
      end;
    DataTypeKind_Structured:
      begin
        WriteLn('The data type is structured.');
        StructuredDataType := DataType as _StructuredDataType;
        WriteLn(Format('It has %s data fields.', [StructuredDataType.DataFields.Count.ToString]));
        ElementEnumerator := StructuredDataType.DataFields.GetEnumerator;
        FieldNames := '';
        First := True;
        while (ElementEnumerator.Next(1, Element, Count) = S_OK) do
        begin
          if First then
            First := False
          else
            FieldNames := FieldNames + ', ';
          FieldNames := FieldNames + Element.Name;
        end;
        WriteLn(Format('The names of the data fields are: %s.', [FieldNames]));

        WriteLn('A dump of each of the data fields follows.');
        ElementEnumerator := StructuredDataType.DataFields.GetEnumerator;
        while (ElementEnumerator.Next(1, Element, Count) = S_OK) do
        begin
          DataField := IUnknown(Element) as _DataField;
          WriteLn;
          WriteLn(Format('dataField.Name: %s', [DataField.Name]));
          // Note that every data field also has properties like IsLength, IsOptional, IsSwitch which might
          // be of interest but we are not dumping them here.
          ProcessDataType(DataField.DataType, 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