AccessibleSelection Enumeration
Specifies how an accessible object is selected or receives focus.
This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.
Namespace: System.Windows.FormsAssembly: System.Windows.Forms (in System.Windows.Forms.dll)
| Member name | Description | |
|---|---|---|
| None | The selection or focus of an object is unchanged. | |
| TakeFocus | Assigns focus to an object and makes it the anchor, which is the starting point for the selection. Can be combined with TakeSelection, ExtendSelection, AddSelection, or RemoveSelection. | |
| TakeSelection | Selects the object and deselects all other objects in the container. | |
| ExtendSelection | Selects all objects between the anchor and the selected object. | |
| AddSelection | Adds the object to the selection. | |
| RemoveSelection | Removes the object from the selection. |
A focused object is the one object that receives keyboard input. The object with the keyboard focus is either the active window or a child object of the active window. A selected object is marked to participate in some type of group operation.
This enumeration is used by AccessibleObject.Select.
For additional information on the accessibility application, search for "Microsoft Active Accessibility" in the Microsoft Developer Network (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. Because 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 AccessibleSelection enumeration with the Select 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
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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.