Was this page helpful?
Your feedback about this content is important. Let us know what you think.
Additional feedback?
1500 characters remaining
Export (0) Print
Expand All

AccessibleObject.Bounds Property

Gets the location and size of the accessible object.

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

'Declaration
Public Overridable ReadOnly Property Bounds As Rectangle

Property Value

Type: System.Drawing.Rectangle
A Rectangle that represents the bounds of the accessible object.

ExceptionCondition
COMException

The bounds of control cannot be retrieved.

The Bounds property retrieves the object's bounding rectangle in screen coordinates. If the object has a nonrectangular shape, then this property represents the smallest rectangle that completely encompasses the entire object region. Therefore, for nonrectangular objects such as list view items, the coordinates of the object's bounding rectangle can fail, if tested, by calling the HitTest method, because HitTest determines the object's boundaries on a pixel-by-pixel basis.

Notes to Inheritors

The default implementation returns the accessible object's bounding rectangle if the object wraps a system control; otherwise, it returns Rectangle.Empty. All visible accessible objects must support this method. Sound objects do not support this method.

The following 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 have 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 code excerpt demonstrates overriding the Bounds property. See the AccessibleObject class overview for the complete code example.

' Inner class CurveLegendAccessibleObject represents accessible information  
' associated with the CurveLegend object. 
Public Class CurveLegendAccessibleObject
    Inherits AccessibleObject

    Private curveLegend As CurveLegend

    Public Sub New(curveLegend As CurveLegend)
        Me.curveLegend = curveLegend
    End Sub 'New 

    ' Private property that helps get the reference to the parent ChartControl.                 
    Private ReadOnly Property ChartControl() As ChartControlAccessibleObject
        Get 
            Return CType(Parent, ChartControlAccessibleObject)
        End Get 
    End Property 

    ' Friend helper function that returns the ID for this CurveLegend.                 
    Friend ReadOnly Property ID() As Integer 
        Get 
            Dim i As Integer 
            For i = 0 To (ChartControl.GetChildCount()) - 1
                If ChartControl.GetChild(i) Is Me Then 
                    Return i
                End If 
            Next i
            Return - 1
        End Get 
    End Property 

    ' Gets the Bounds for the CurveLegend. This is used by accessibility programs. 
    Public Overrides ReadOnly Property Bounds() As Rectangle
        Get 
            ' The bounds is in screen coordinates. 
            Dim loc As Point = curveLegend.Location
            Return New Rectangle(curveLegend.chart.PointToScreen(loc), curveLegend.Size)
        End Get 
    End Property 

    ' Gets or sets the Name for the CurveLegend. This is used by accessibility programs.                 
    Public Overrides Property Name() As String 
        Get 
            Return curveLegend.Name
        End Get 
        Set
            curveLegend.Name = value
        End Set 
    End Property 

    ' Gets the Curve Legend Parent's Accessible object. 
    ' This is used by accessibility programs.                 
    Public Overrides ReadOnly Property Parent() As AccessibleObject
        Get 
            Return curveLegend.chart.AccessibilityObject
        End Get 
    End Property 

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

    ' Gets the state based on the selection for the CurveLegend.  
    ' This is used by accessibility programs.                 
    Public Overrides ReadOnly Property State() As AccessibleStates
        Get 
            Dim stateTemp As AccessibleStates = AccessibleStates.Selectable
            If curveLegend.Selected Then
                stateTemp = stateTemp Or AccessibleStates.Selected
            End If 
            Return stateTemp
        End Get 
    End Property 

    ' Navigates through siblings of this CurveLegend. This is used by accessibility programs.                 
    Public Overrides Function Navigate(navdir As AccessibleNavigation) As AccessibleObject
        ' Use the Friend NavigateFromChild helper function that exists 
        ' on ChartControlAccessibleObject. 
        Return ChartControl.NavigateFromChild(Me, navdir)
    End Function 

    ' Selects or unselects this CurveLegend. This is used by accessibility programs. 
    Public Overrides Sub [Select](selection As AccessibleSelection)

        ' Use the internal SelectChild helper function that exists 
        ' on ChartControlAccessibleObject.
        ChartControl.SelectChild(Me, selection)
    End Sub 

End Class 'CurveLegendAccessibleObject

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
Show:
© 2015 Microsoft