Infragistics(R) NetAdvantage(R) Windows Forms
OnSubObjectPropChanged Method
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Infragistics.Win.UltraWinGrid Namespace > UltraGridRow Class : OnSubObjectPropChanged Method

propChange
A structure containing the property change information.
Called when a property has changed on a sub object

Syntax

Visual Basic (Declaration) 
Protected Overrides Sub OnSubObjectPropChanged( _
   ByVal propChange As Infragistics.Shared.PropChangeInfo _
) 
C# 
protected override void OnSubObjectPropChanged( 
   Infragistics.Shared.PropChangeInfo propChange
)

Parameters

propChange
A structure containing the property change information.

Example

The following sample code illustrates how classes derived from SubObjectBase can provide property change notifications with complete context information even within complex object graphs.


Also note that the SubObjectPropChanged event is public so that an application developer can also hook into the event chain at any point.

For an overview of how to handle events in Visual Basic or Visual C#, see Event Handlers in Visual Basic and Visual C#. For specific information and code examples illustrating how to consume events in your application, see Consuming Events in the .NET Framework Developer's Guide.

Visual BasicCopy Code
Imports Infragistics.Shared
Imports Infragistics.Win

Public Class ExampleClass
    Inherits SubObjectBase

    Private appearanceHolder As appearanceHolder
    Private enabledValue As Boolean

    ' Listens for property change notifications of the object's sub objects.
    Protected Overrides Sub OnSubObjectPropChanged(ByVal pci As Infragistics.Shared.PropChangeInfo)

        ' Check if the source is our appearance object.
        If Not Me.appearanceHolder Is Nothing _
        AndAlso pci.Source.Equals(Me.appearanceHolder.RootAppearance) Then

            ' Do what needs to be done (if anything) based on the 
            ' nature of the change
            Dim propId As AppearancePropIds

            propId = pci.PropId

            If propId = AppearancePropIds.Image _
            OrElse propId = AppearancePropIds.ImageHAlign _
            OrElse propId = AppearancePropIds.ImageVAlign Then
                Me.DirtyImage()
            Else
                Me.DirtyText()
            End If

            ' Call NotifyPropChange with the appropriate property id
            ' and the PropChangeInfo instance that was passed into
            ' this method.
            Me.NotifyPropChange(StatusBarPropertyIds.Appearance, pci)

            ' Note: If there are any listeners to our 'SubObjectPropChanged' 
            ' event, the event will be raised with a new PropChangeInfo
            ' event argument whose properties will be set as follows:
            ' 1. The Source property will refer to this object.
            ' 2. The PropId property will be StatusBarPropertyIds.Appearance.
            ' 3. The Trigger property will be the passed in PropChangeInfo.
            '
            ' This will effectively create a chain of PropChangeInfo
            ' objects, with the new one at the head, that exposes
            ' complete context information regarding the change. 
            Return
        End If

        ' There is an overload to the 'NotifyPropChange' method
        ' that just takes the passed in PropChangeInfo object.
        ' This is useful if you want to pass the notification
        ' along to this object's listeners 'as is'. In other words,
        ' without creating a new PropChangeInfo to add to the 
        ' head of the chain (refer to above comments).
        Me.NotifyPropChange(pci)

        Dim sb As System.Text.StringBuilder

        ' The following code walks up the PropChangeInfo chain
        ' and writes out the source and property id of each
        ' object.
        While Not pci Is Nothing

            sb = New System.Text.StringBuilder()

            sb.Append("Property Id: ")
            sb.Append(pci.PropId.ToString())
            sb.Append(", source: ")
            sb.Append(pci.Source.ToString())
            sb.Append(". type: ")
            sb.Append(pci.Source.GetType().ToString())

            Debug.WriteLine(sb.ToString())
            Debug.Indent()
        End While

        ' Get the next PropChangeInfo object in the chain 
        pci = pci.Trigger

        ' Reset the indent level of the Debug object
        Debug.IndentLevel = 0

        ' Alternatively there are 'Find...' methods that
        ' will walk up the chain until they find the 
        ' requested PropChangeInfo object to return or
        ' they will return null.
        pci = pci.FindPropId(AppearancePropIds.BackGradientStyle)
        pci = pci.FindTrigger(Me.appearanceHolder.RootAppearance)

        ' There is also a 'FindSource' method which will
        ' return the source object based on the passed
        ' in type. If no source object of that type is
        ' found in the chain this method will return null.
        Dim source As Object
        source = pci.FindSource(GetType(Infragistics.Win.Appearance))

    End Sub

    Public Property Enabled() As Boolean

        Get
            Return Me.enabledValue
        End Get

        Set(ByVal Value As Boolean)
            If Not Me.enabledValue = Value Then
                Me.enabledValue = Value

                ' Call the overload to the 'NotifyPropChange' method
                ' that just takes a property id. 
                Me.NotifyPropChange(StatusBarPropertyIds.Enabled)

                ' Note: If there are any listeners to our 'SubObjectPropChanged' 
                ' event, the event will be raised with a PropChangeInfo
                ' event argument whose properties will be` set as follows:
                ' 1. The Source property will refer to this object.
                ' 2. The PropId property will be StatusBarPropertyIds.Enabled.
                ' 3. The Trigger property will be null.
            End If
        End Set

    End Property

    Public ReadOnly Property Appearance() As AppearanceBase

        Get
            ' Lazily create the appearance holder
            If Me.appearanceHolder Is Nothing Then

                Me.appearanceHolder = New AppearanceHolder()

                ' Listen in to property changes generated by the
                ' object. When one of its properties changes our 
                ' 'OnSubObjectPropChanged' method will be called.
                AddHandler Me.appearanceHolder.SubObjectPropChanged, Me.SubObjectPropChangeHandler
            End If

            Return Me.appearanceHolder.Appearance

        End Get

    End Property

    Protected Overrides Sub OnDispose()

        If Not Me.appearanceHolder Is Nothing Then
            ' Remove ourselves as a listener
            RemoveHandler Me.appearanceHolder.SubObjectPropChanged, Me.SubObjectPropChangeHandler
        End If

    End Sub

    Private Sub DirtyImage()
    End Sub

    Private Sub DirtyText()
    End Sub
End Class

Public Enum StatusBarPropertyIds
    Appearance = 1
    Enabled = 2
End Enum
C#Copy Code
using System;
using System.Diagnostics;
using Infragistics.Shared;
using Infragistics.Win;

namespace SharedSnippets
{
	public class ExampleClass : SubObjectBase
	{
		private AppearanceHolder appearanceHolder = null;
		private bool			 enabled = true;

		// Listens for property change notifications of the object's sub objects.
		protected override void OnSubObjectPropChanged( PropChangeInfo pci )
		{
			// Check if the source is our appearance object.
			if (this.appearanceHolder != null && 
				pci.Source == this.appearanceHolder.RootAppearance)
			{
				// Do what needs to be done (if anything) based on the 
				// nature of the change
				switch ( (AppearancePropIds)pci.PropId )
				{
					case AppearancePropIds.Image:
					case AppearancePropIds.ImageHAlign:
					case AppearancePropIds.ImageVAlign:
					{
						this.DirtyImage();
						break;
					}
					default:
						this.DirtyText();
						break;
				}

				// Call NotifyPropChange with the appropriate property id
				// and the PropChangeInfo instance that was passed into
				// this method.
				this.NotifyPropChange( StatusBarPropertyIds.Appearance, pci );

				// Note: If there are any listeners to our 'SubObjectPropChanged' 
				// event, the event will be raised with a new PropChangeInfo
				// event argument whose properties will be set as follows:
				// 1. The Source property will refer to this object.
				// 2. The PropId property will be StatusBarPropertyIds.Appearance.
				// 3. The Trigger property will be the passed in PropChangeInfo.
				//
				// This will effectively create a chain of PropChangeInfo
				// objects, with the new one at the head, that exposes
				// complete context information regarding the change. 
				
				return;
			}

			// There is an overload to the 'NotifyPropChange' method
			// that just takes the passed in PropChangeInfo object.
			// This is useful if you want to pass the notification
			// along to this object's listeners 'as is'. In other words,
			// without creating a new PropChangeInfo to add to the 
			// head of the chain (refer to above comments).
			this.NotifyPropChange( pci );
			
			// The following code walks up the PropChangeInfo chain
			// and writes out the source and property id of each
			// object.
			while ( pci != null )
			{
				System.Text.StringBuilder sb = new System.Text.StringBuilder();
				
				sb.Append("Property Id: ");
				sb.Append(pci.PropId.ToString());
				sb.Append(", source: ");
				sb.Append(pci.Source.ToString());
				sb.Append(". type: ");
				sb.Append(pci.Source.GetType().ToString());

				Debug.WriteLine( sb.ToString() );
				Debug.Indent();

				// Get the next PropChangeInfo object in the chain 
				pci = pci.Trigger;
			}

			// Reset the indent level of the Debug object
			Debug.IndentLevel = 0;

			// Alternatively there are 'Find...' methods that
			// will walk up the chain until they find the 
			// requested PropChangeInfo object to return or
			// they will return null.
			pci = pci.FindPropId( AppearancePropIds.BackGradientStyle );
			pci = pci.FindTrigger( this.appearanceHolder.RootAppearance );

			// There is also a 'FindSource' method which will
			// return the source object based on the passed
			// in type. If no source object of that type is
			// found in the chain this method will return null.
			object source = pci.FindSource( typeof(Infragistics.Win.Appearance ) );

		}

		public bool Enabled
		{

			get { return this.enabled; }

			set
			{
				if (this.enabled != value)
				{
					this.enabled = value;

					// Call the overload to the 'NotifyPropChange' method
					// that just takes a property id. 
					this.NotifyPropChange( StatusBarPropertyIds.Enabled );

					// Note: If there are any listeners to our 'SubObjectPropChanged' 
					// event, the event will be raised with a PropChangeInfo
					// event argument whose properties will be` set as follows:
					// 1. The Source property will refer to this object.
					// 2. The PropId property will be StatusBarPropertyIds.Enabled.
					// 3. The Trigger property will be null.
				}
			}

		}

		public AppearanceBase Appearance
		{

			get
			{
				// Lazily create the appearance holder
				if (this.appearanceHolder == null)
				{
					this.appearanceHolder = new AppearanceHolder();

					// Listen in to property changes generated by the
					// object. When one of its properties changes our 
					// 'OnSubObjectPropChanged' method will be called.
					this.appearanceHolder.SubObjectPropChanged += this.SubObjectPropChangeHandler;
				}
				return this.appearanceHolder.Appearance;
			}

		}

		protected override void OnDispose()
		{

			if ( this.appearanceHolder != null )
			{
				// Remove ourselves as a listener
				this.appearanceHolder.SubObjectPropChanged -= this.SubObjectPropChangeHandler;
			}

		} 

		private void DirtyImage(){} 
		private void DirtyText(){} 
	}

	public enum StatusBarPropertyIds
	{
		Appearance = 1,
		Enabled = 2
	}
}

See Also