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AccessibleNavigation Enumeration

Specifies values for navigating among accessible objects.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

'Declaration
Public Enumeration AccessibleNavigation
'Usage
Dim instance As AccessibleNavigation

Member nameDescription
DownNavigation to a sibling object located below the starting object.
FirstChildNavigation to the first child of the object.
LastChildNavigation to the last child of the object.
LeftNavigation to the sibling object located to the left of the starting object.
NextNavigation to the next logical object, typically from a sibling object to the starting object.
PreviousNavigation to the previous logical object, typically from a sibling object to the starting object.
RightNavigation to the sibling object located to the right of the starting object.
UpNavigation to a sibling object located above the starting object.

Accessible navigation directions are either spatial (up, down, left, and right) or logical (first child, last child, next, and previous). Logical directions are used when clients navigate from one user interface element to another within the same container.

AccessibleObject uses this enumeration.

For more information about the accessibility application, search for the "Microsoft Active Accessibility" topic in the MSDN library.

The following code example demonstrates the creation of an accessibility-aware chart control, using the AccessibleObject and Control.ControlAccessibleObject classes to expose accessible information. The control plots two curves along with a legend. The ChartControlAccessibleObject class, which derives from ControlAccessibleObject, is used in the CreateAccessibilityInstance method to provide custom accessible information for the chart control. Since the chart legend is not an actual Control -based control, but instead is drawn by the chart control, it does not any built-in accessible information. Because of this, the ChartControlAccessibleObject class overrides the GetChild method to return the CurveLegendAccessibleObject that represents accessible information for each part of the legend. When an accessible-aware application uses this control, the control can provide the necessary accessible information.

This example demonstrates using the AccessibleNavigation enumeration with the Navigate method. See the AccessibleObject class overview for the complete code example.

' Inner Class ChartControlAccessibleObject represents accessible information  
' associated with the ChartControl. 
' The ChartControlAccessibleObject is returned in the         ' ChartControl.CreateAccessibilityInstance override. 
Public Class ChartControlAccessibleObject
    Inherits Control.ControlAccessibleObject

    Private chartControl As ChartControl

    Public Sub New(ctrl As ChartControl)
        MyBase.New(ctrl)
        chartControl = ctrl
    End Sub 'New 

    ' Get the role for the Chart. This is used by accessibility programs.             
    Public Overrides ReadOnly Property Role() As AccessibleRole
        Get 
            Return System.Windows.Forms.AccessibleRole.Chart
        End Get 
    End Property 

    ' Get the state for the Chart. This is used by accessibility programs.             
    Public Overrides ReadOnly Property State() As AccessibleStates
        Get 
            Return AccessibleStates.ReadOnly 
        End Get 
    End Property                         

    ' The CurveLegend objects are "child" controls in terms of accessibility so  
    ' return the number of ChartLengend objects.             
    Public Overrides Function GetChildCount() As Integer 
        Return chartControl.Legends.Length
    End Function  

    ' Get the Accessibility object of the child CurveLegend idetified by index. 
    Public Overrides Function GetChild(index As Integer) As AccessibleObject
        If index >= 0 And index < chartControl.Legends.Length Then 
            Return chartControl.Legends(index).AccessibilityObject
        End If 
        Return Nothing 
    End Function  

    ' Helper function that is used by the CurveLegend's accessibility object 
    ' to navigate between sibiling controls. Specifically, this function is used in 
    ' the CurveLegend.CurveLegendAccessibleObject.Navigate function. 
    Friend Function NavigateFromChild(child As CurveLegend.CurveLegendAccessibleObject, _
                                    navdir As AccessibleNavigation) As AccessibleObject
        Select Case navdir
            Case AccessibleNavigation.Down, AccessibleNavigation.Next 
                    Return GetChild(child.ID + 1)

            Case AccessibleNavigation.Up, AccessibleNavigation.Previous
                    Return GetChild(child.ID - 1)
        End Select 
        Return Nothing 
    End Function             

    ' Helper function that is used by the CurveLegend's accessibility object 
    ' to select a specific CurveLegend control. Specifically, this function is used  
    ' in the CurveLegend.CurveLegendAccessibleObject.Select function.             
    Friend Sub SelectChild(child As CurveLegend.CurveLegendAccessibleObject, selection As AccessibleSelection)
        Dim childID As Integer = child.ID

        ' Determine which selection action should occur, based on the 
        ' AccessibleSelection value. 
        If (selection And AccessibleSelection.TakeSelection) <> 0 Then 
            Dim i As Integer 
            For i = 0 To chartControl.Legends.Length - 1
                If i = childID Then
                    chartControl.Legends(i).Selected = True 
                Else
                    chartControl.Legends(i).Selected = False 
                End If 
            Next i

            ' AccessibleSelection.AddSelection means that the CurveLegend will be selected. 
            If (selection And AccessibleSelection.AddSelection) <> 0 Then
                chartControl.Legends(childID).Selected = True 
            End If 

            ' AccessibleSelection.AddSelection means that the CurveLegend will be unselected.                     
            If (selection And AccessibleSelection.RemoveSelection) <> 0 Then
                chartControl.Legends(childID).Selected = False 
            End If 
        End If 
    End Sub 'SelectChild
End Class 'ChartControlAccessibleObject

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
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