ExtensionObject Class

An object used to wrap data types that the receiver may not understand.

Object Model

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<DataContractAttribute("http://opcfoundation.org/UA/2008/02/Types.xsd")>
Public Class ExtensionObject

'Usage
 
Dim instance As ExtensionObject

[DataContract("http://opcfoundation.org/UA/2008/02/Types.xsd")]
public class ExtensionObject

[DataContract("http://opcfoundation.org/UA/2008/02/Types.xsd")]
public ref class ExtensionObject

Remarks

This class is a wrapper/helper class for storing data types that a receiver might not understand, or be prepared to handle. This class may use System.Reflection to analyze an object and retrieve the values of its public properties directly, and then encode those into a string representation that can then be easily encoded as a single string.

An instance of the ExtensionObject is a container for any complex data types which cannot be encoded as one of the other built-in data types. The ExtensionObject contains a complex value serialized as a sequence of bytes or as an XML element. It also contains an identifier which indicates what data it contains and how it is encoded.

Example

The following example demonstrates a simple class containing 3 public properties of type int, DateTime and string. This class implements the IEncodeable interface, and is then encoded using the WriteExtensionObject method.

C#
Visual Basic

//First, we will define a very simple class object that will represent
//some real-world process.
class simpleClass : IEncodeable
{
             
    //fields
    public string PublicFieldNotVisible = "I should not be encoded";
 
    //properties
    private string stringField;
    public string StringProperty
    {
        get
        {
            return (stringField);
        }
        set
        {
            stringField = value;
        }
    }
             
    private int intField;
    public int IntProperty
    {
        get
        {
            return (intField);
        }
        set
        {
            intField = value;
        }
    }
 
    private DateTime datetimeField;
    public DateTime DatetimeProperty
    {
        get
        {   
            return (datetimeField);
        }
        set
        {
            datetimeField = value;
        }
    }
             
    //class constructor
    public simpleClass(string StringValue, int IntValue, DateTime DateTimeValue)
    {
        StringProperty = StringValue;
        IntProperty = IntValue;
        DatetimeProperty = DateTimeValue;
    }
    public simpleClass(simpleClass SimpleClassInstance)
    {
        StringProperty = SimpleClassInstance.StringProperty;
        IntProperty = SimpleClassInstance.IntProperty;
        DatetimeProperty = SimpleClassInstance.DatetimeProperty;
    }
             
    #region IEncodeable Members
             
    public ExpandedNodeId TypeId
    {
        get
        {
            return (new ExpandedNodeId(Guid.NewGuid()));
        }
    }
             
    public void Encode(IEncoder encoder)
    {
        if (encoder != null)
        {
            //our simple object has 3 properies: string, int and datetime
            encoder.WriteString("StringProperty", this.StringProperty);
            encoder.WriteInt32("IntProperty", this.IntProperty);
            encoder.WriteDateTime("DateTimeProperty", this.DatetimeProperty);
        }
    }
             
    public void Decode(IDecoder decoder)
    {
        if (decoder != null)
        {
            this.StringProperty = decoder.ReadString("StringProperty");
            this.IntProperty = decoder.ReadInt16("IntProperty");
            this.DatetimeProperty = decoder.ReadDateTime("DateTimeProperty");
        }
    }
             
    public bool IsEqual(IEncodeable encodeable)
    {
        return (encodeable.Equals(this));
    }
             
    #endregion
             
    #region ICloneable Members
             
    public new object MemberwiseClone()
    {
        return (new simpleClass(this));
    }
             
    #endregion
             
}
             
public void EncodeExample()
{
    //define an instance of our class object, defined above.
    simpleClass mySimpleClassInstance1 = new simpleClass("String", int.MaxValue, DateTime.Now);
             
    //define an object that will encapsulate/extend our simple instance above
    ExtensionObject extendedSimpleClassInstance = new ExtensionObject(mySimpleClassInstance1);
             
    /// 
    //encode our class object into the stream
    uaEncoderInstance.WriteExtensionObject( "Extended1", extendedSimpleClassInstance);
}

'First, we will define a very simple class object that will represent
 'some real-world process.
 
 Class simpleClass
    Inherits IEncodeable
    
    'fields
    Public PublicFieldNotVisible As String = "I should not be encoded"
    
    'properties
    Private stringField As String
    Private intField As Integer
    Private datetimeField As DateTime
    
    'class constructor
    Public Sub New(ByVal StringValue As String, ByVal IntValue As Integer, ByVal DateTimeValue As DateTime)
        StringProperty = StringValue
        IntProperty = IntValue
        DatetimeProperty = DateTimeValue
    End Sub
    
    Public Sub New(ByVal SimpleClassInstance As simpleClass)
        StringProperty = SimpleClassInstance.StringProperty
        IntProperty = SimpleClassInstance.IntProperty
        DatetimeProperty = SimpleClassInstance.DatetimeProperty
    End Sub
    
    Public Property StringProperty As String
        Get
            Return stringField
        End Get
        Set
            stringField = value
        End Set
    End Property
    
    Public Property IntProperty As Integer
        Get
            Return intField
        End Get
        Set
            intField = value
        End Set
    End Property
    
    Public Property DatetimeProperty As DateTime
        Get
            Return datetimeField
        End Get
        Set
            datetimeField = value
        End Set
    End Property
    
    Public ReadOnly Property TypeId As ExpandedNodeId
        Get
            Return New ExpandedNodeId(Guid.NewGuid)
        End Get
    End Property
    
    Public Sub Encode(ByVal encoder As IEncoder)
        If encoder Isnot Nothing Then
            'our simple object has 3 properies: string, int and datetime
            encoder.WriteString("StringProperty", Me.StringProperty)
            encoder.WriteInt32("IntProperty", Me.IntProperty)
            encoder.WriteDateTime("DateTimeProperty", Me.DatetimeProperty)
        End If
    End Sub
    
    Public Sub Decode(ByVal decoder As IDecoder)
        If decoder Isnot Nothing Then
            Me.StringProperty = decoder.ReadString("StringProperty")
            Me.IntProperty = decoder.ReadInt16("IntProperty")
            Me.DatetimeProperty = decoder.ReadDateTime("DateTimeProperty")
        End If
    End Sub
    
    Public Function IsEqual(ByVal encodeable As IEncodeable) As Boolean
        Return encodeable.Equals(Me)
    End Function
    
    Public Function Clone() As Object
        Return New simpleClass(Me)
    End Function
End Class
            
   Public Sub nodeid()
    'define an instance of our class object, defined above.
    Dim mySimpleClassInstance1 As simpleClass = New simpleClass("String", int.MaxValue, DateTime.Now)
 
    'define an object that will encapsulate/extend our simple instance above
    Dim extendedSimpleClassInstance As ExtensionObject = New ExtensionObject(mySimpleClassInstance1)
 
    'encode our class object into the stream
    uaEncoderInstance.WriteExtensionObject("Extended1", extendedSimpleClassInstance)
End Sub

Inheritance Hierarchy

System.Object
Opc.Ua.ExtensionObject

Requirements

Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

Reference

ExtensionObject Members
Opc.Ua Namespace