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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.

[Visual Basic]
<Flags>
<Serializable>
Public Enum AccessibleSelection
[C#]
[Flags]
[Serializable]
public enum AccessibleSelection
[C++]
[Flags]
[Serializable]
__value public enum AccessibleSelection
[JScript]
public
   Flags
 Serializable
enum AccessibleSelection

Remarks

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.

Members

Member name Description Value
AddSelection Adds the object to the selection. 8
ExtendSelection Selects all objects between the anchor and the selected object. 4
None The selection or focus of an object is unchanged. 0
RemoveSelection Removes the object from the selection. 16
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. 1
TakeSelection Selects the object and deselects all other objects in the container. 2

Example

[Visual Basic, C#, C++] 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 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.

[Visual Basic, C#, C++] This code excerpt demonstrates using the AccessibleSelection enumeration with the Select method. See the AccessibleObject class overview for the complete code example.

[Visual Basic] 
' 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

[C#] 
// Inner class ChartControlAccessibleObject represents accessible information associated with the ChartControl.
// The ChartControlAccessibleObject is returned in the ChartControl.CreateAccessibilityInstance override.
public class ChartControlAccessibleObject : ControlAccessibleObject
{
    ChartControl chartControl;

    public ChartControlAccessibleObject(ChartControl ctrl) : base(ctrl) 
    {
        chartControl = ctrl;
    }

    // Gets the role for the Chart. This is used by accessibility programs.
    public override AccessibleRole Role
    {  
        get {
            return AccessibleRole.Chart;
        }
    }

    // Gets the state for the Chart. This is used by accessibility programs.
    public override AccessibleStates State
    {  
        get {                    
            return AccessibleStates.ReadOnly;
        }
    }

    // The CurveLegend objects are "child" controls in terms of accessibility so 
    // return the number of ChartLengend objects.
    public override int GetChildCount()
    {  
        return chartControl.Legends.Length;
    }

    // Gets the Accessibility object of the child CurveLegend idetified by index.
    public override AccessibleObject GetChild(int index)
    {  
        if (index >= 0 && index < chartControl.Legends.Length) {
            return chartControl.Legends[index].AccessibilityObject;
        }                
        return null;
    }

    // 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.
    internal AccessibleObject NavigateFromChild(CurveLegend.CurveLegendAccessibleObject child, 
                                                AccessibleNavigation navdir) 
    {  
        switch(navdir) {
            case AccessibleNavigation.Down:
            case AccessibleNavigation.Next:
                return GetChild(child.ID + 1);
                
            case AccessibleNavigation.Up:
            case AccessibleNavigation.Previous:
                return GetChild(child.ID - 1);                        
        }
        return null;
    }

    // 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.
    internal void SelectChild(CurveLegend.CurveLegendAccessibleObject child, AccessibleSelection selection) 
    {   
        int childID = child.ID;

        // Determine which selection action should occur, based on the
        // AccessibleSelection value.
        if ((selection & AccessibleSelection.TakeSelection) != 0) {
            for(int i = 0; i < chartControl.Legends.Length; i++) {
                if (i == childID) {
                    chartControl.Legends[i].Selected = true;                        
                } else {
                    chartControl.Legends[i].Selected = false;
                }
            }

            // AccessibleSelection.AddSelection means that the CurveLegend will be selected.
            if ((selection & AccessibleSelection.AddSelection) != 0) {
                chartControl.Legends[childID].Selected = true;                        
            }

            // AccessibleSelection.AddSelection means that the CurveLegend will be unselected.
            if ((selection & AccessibleSelection.RemoveSelection) != 0) {
                chartControl.Legends[childID].Selected = false;                        
            }
        }            
    }
}

[C++] 
// Inner class ChartControlAccessibleObject represents accessible information associated with the ChartControl.
// The ChartControlAccessibleObject is returned in the ChartControl::CreateAccessibilityInstance .
__gc class ChartControlAccessibleObject : public ControlAccessibleObject {
   ChartControl* chartControl;

public:
   ChartControlAccessibleObject(ChartControl* ctrl) : ControlAccessibleObject (ctrl) {
      chartControl = ctrl;
   }

   // Gets the role for the Chart. This is used by accessibility programs.
   __property System::Windows::Forms::AccessibleRole get_Role() {
      return AccessibleRole::Chart;
   }

   // Gets the state for the Chart. This is used by accessibility programs.
   __property AccessibleStates get_State() {
      return AccessibleStates::ReadOnly;
   }

   // The CurveLegend objects are "child" controls in terms of accessibility so
   // return the number of ChartLengend objects.
   int GetChildCount() {
      return chartControl->Legends->Length;
   }

   // Gets the Accessibility object of the child CurveLegend idetified by index.
   AccessibleObject* GetChild(int index) {
      if (index >= 0 && index < chartControl->Legends->Length) {
         return chartControl->Legends[index]->AccessibilityObject;
      }
      return 0;
   }

   // 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.
public private:
   AccessibleObject* NavigateFromChild(CurveLegend::CurveLegendAccessibleObject* child,
      AccessibleNavigation navdir) {
         switch(navdir) {
                 case AccessibleNavigation::Down:
                 case AccessibleNavigation::Next:
                    return GetChild(child->ID + 1);

                 case AccessibleNavigation::Up:
                 case AccessibleNavigation::Previous:
                    return GetChild(child->ID - 1);
         }
         return 0;
      }

      // 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.
      void SelectChild(CurveLegend::CurveLegendAccessibleObject* child, AccessibleSelection selection) {
         int childID = child->ID;

         // Determine which selection action should occur, based on the
         // AccessibleSelection value.
         if ((selection & AccessibleSelection::TakeSelection) != 0) {
            for (int i = 0; i < chartControl->Legends->Length; i++) {
               if (i == childID) {
                  chartControl->Legends[i]->Selected = true;
               } else {
                  chartControl->Legends[i]->Selected = false;
               }
            }

            // AccessibleSelection->AddSelection means that the CurveLegend will be selected.
            if ((selection & AccessibleSelection::AddSelection) != 0) {
               chartControl->Legends[childID]->Selected = true;
            }

            // AccessibleSelection->AddSelection means that the CurveLegend will be unselected.
            if ((selection & AccessibleSelection::RemoveSelection) != 0) {
               chartControl->Legends[childID]->Selected = false;
            }
         }
      }
}; // class ChartControlAccessibleObject

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Namespace: System.Windows.Forms

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

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

See Also

System.Windows.Forms Namespace | AccessibleEvents | AccessibleNavigation | AccessibleObject | AccessibleRole | AccessibleStates

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