AccessibleObject 类

提供辅助功能应用程序用于调整应用程序的用户界面 (UI) 的信息,以方便有障碍用户使用。

**命名空间:**System.Windows.Forms
**程序集:**System.Windows.Forms(在 system.windows.forms.dll 中)

语法

声明
<ComVisibleAttribute(True)> _
Public Class AccessibleObject
    Inherits StandardOleMarshalObject
    Implements IReflect, IAccessible
用法
Dim instance As AccessibleObject
[ComVisibleAttribute(true)] 
public class AccessibleObject : StandardOleMarshalObject, IReflect, IAccessible
[ComVisibleAttribute(true)] 
public ref class AccessibleObject : public StandardOleMarshalObject, IReflect, IAccessible
/** @attribute ComVisibleAttribute(true) */ 
public class AccessibleObject extends StandardOleMarshalObject implements IReflect, IAccessible
ComVisibleAttribute(true) 
public class AccessibleObject extends StandardOleMarshalObject implements IReflect, IAccessible

备注

辅助功能应用程序可以调整应用程序的功能,以便为残疾人士用户改进使用性。

对于视觉有障碍的用户,您可以调整软件和操作系统的功能来满足他们的需要。例如,您可以放大文本和图像,并以对比的方式来呈现它们。另外,您可以通过对颜色的恰当使用来适应色盲用户的需要。如果是有严重视觉障碍的用户,使用计算机时可通过屏幕检查功能,将屏幕文本转换为语音或转换为动态的、可刷新的盲文显示。

对于听觉有障碍的用户,您可以设计具有视觉提示(例如闪烁的工具栏)的程序,也可以将语音消息作为文本显示。例如,当 SoundSentry 功能(“控制面板”中的辅助功能选项)打开时,它将在系统发出警报声音时提供视觉警告。

对于行动不便的用户,您可以设计简化或消除键盘和鼠标使用的控件,从而改进计算机的可使用性。“控制面板”会提供帮助。例如,一种选择是使用数字键盘而不是鼠标来定位。另一选项,名为 StickyKeys,使那些不能同时按住两个或多个键(例如 Ctrl+P)的用户可以一次只按一个键,也能获得相同的结果。

对于有认知障碍和语言障碍的用户,您可以设计软件程序来更好地适应他们的需要。例如,使用明显的或带有提示的操作顺序安排、简单的显示、较少的文字以及面向小学标准的阅读程度,会有益于这些用户使用。

对于会突然发病的用户,您可以设计软件程序来消除导致发病的因素。

有关辅助功能的更多信息,包括关于辅助功能应用程序的更多信息,请参见 MSDN Library 或 Microsoft 网站中关于“Microsoft 辅助功能”的文档。

Note注意

若要使用 AccessibleObject,则必须添加对 Accessibility 程序集的引用,该程序集是随 .NET Framework 一起安装的。

给继承者的说明 从此类中继承时,您可以重写所有成员。

示例

下面的代码示例演示如何创建一个具有辅助功能的图表控件,并使用 AccessibleObjectControl.ControlAccessibleObject 类来公开辅助性信息。该控件绘制两条带有图例的曲线。CreateAccessibilityInstance 方法使用从 ControlAccessibleObject 派生的 ChartControlAccessibleObject 类,为图表控件提供自定义辅助性信息。因为图表图例不是实际的基于 Control 的控件,而是由图表控件绘制的,所以它不提供任何内置的辅助性信息。因此,ChartControlAccessibleObject 类重写 GetChild 方法以返回 CurveLegendAccessibleObject(表示该图例各部分的辅助性信息)。当具有辅助功能的应用程序使用该控件时,该控件能提供必需的辅助性信息。

Option Explicit

Imports System
Imports System.Drawing
Imports System.Windows.Forms

Namespace ChartControlNameSpace
    
    Public Class Form1 
        Inherits System.Windows.Forms.Form

        ' Test out the Chart Control.
        Private chart1 As ChartControl

        <System.STAThread()> _
        Public Shared Sub Main()
            System.Windows.Forms.Application.Run(New Form1())
        End Sub 'Main

        Public Sub New() 
            ' Create a chart control and add it to the form.
            Me.chart1 = New ChartControl()
            Me.ClientSize = New System.Drawing.Size(920, 566)

            Me.chart1.Location = New System.Drawing.Point(47, 16)
            Me.chart1.Size = New System.Drawing.Size(600, 400)

            Me.Controls.Add(Me.chart1)
        End Sub
    End Class

    ' Declares a chart control that demonstrates Accessibility in Windows Forms.
    Public Class ChartControl
        Inherits System.Windows.Forms.UserControl

        Private legend1 As CurveLegend
        Private legend2 As CurveLegend
        
        Public Sub New()
            ' The ChartControl draws the chart in the OnPaint override.
            SetStyle(ControlStyles.ResizeRedraw, True)
            SetStyle(ControlStyles.DoubleBuffer, True)
            SetStyle(ControlStyles.AllPaintingInWmPaint, True)
            
            Me.BackColor = System.Drawing.Color.White
            Me.Name = "ChartControl"

            ' The CurveLengend is not Control-based, it just
            ' represent the parts of the legend.
            legend1 = New CurveLegend(Me, "A")
            legend1.Location = New Point(20, 30)
            legend2 = New CurveLegend(Me, "B")
            legend2.Location = New Point(20, 50)
        End Sub 'New
              
        ' Overridden to return the custom AccessibleObject 
        ' for the entire chart.
        Protected Overrides Function CreateAccessibilityInstance() As AccessibleObject
            Return New ChartControlAccessibleObject(Me)
        End Function 

        Protected Overrides Sub OnPaint(e As PaintEventArgs)
            ' The ChartControl draws the chart in the OnPaint override.
            MyBase.OnPaint(e)
            
            Dim bounds As Rectangle = Me.ClientRectangle
            Dim border As Integer = 5
            
            ' Draw the legends first.
            Dim format As New StringFormat()
            format.Alignment = StringAlignment.Center
            format.LineAlignment = StringAlignment.Center
            
            If Not (legend1 Is Nothing) Then
                If legend1.Selected Then
                    e.Graphics.FillRectangle(New SolidBrush(Color.Blue), legend1.Bounds)
                Else
                    e.Graphics.DrawRectangle(Pens.Blue, legend1.Bounds)
                End If
                e.Graphics.DrawString(legend1.Name, Me.Font, Brushes.Black, RectangleF.op_Implicit(legend1.Bounds), format)
            End If
            If Not (legend2 Is Nothing) Then
                If legend2.Selected Then
                    e.Graphics.FillRectangle(New SolidBrush(Color.Red), legend2.Bounds)
                Else
                    e.Graphics.DrawRectangle(Pens.Red, legend2.Bounds)
                End If
                e.Graphics.DrawString(legend2.Name, Me.Font, Brushes.Black, RectangleF.op_Implicit(legend2.Bounds), format)
            End If
            
            ' Chart out the actual curves that represent data in the Chart.
            bounds.Inflate(-border, -border)
            Dim curve1() As Point = {New Point(bounds.Left, bounds.Bottom), _
                                     New Point(bounds.Left + bounds.Width / 3, bounds.Top + bounds.Height / 5), _
                                     New Point(bounds.Right - bounds.Width / 3,(bounds.Top + bounds.Bottom) / 2), _
                                     New Point(bounds.Right, bounds.Top)}

            Dim curve2() As Point = {New Point(bounds.Left, bounds.Bottom - bounds.Height / 3), _
                                     New Point(bounds.Left + bounds.Width / 3, bounds.Top + bounds.Height / 5), _
                                     New Point(bounds.Right - bounds.Width / 3,(bounds.Top + bounds.Bottom) / 2), _
                                     New Point(bounds.Right, bounds.Top + bounds.Height / 2)}
            
            ' Draw the actual curve only if it is selected.
            If legend1.Selected Then
                e.Graphics.DrawCurve(Pens.Blue, curve1)
            End If
            If legend2.Selected Then
                e.Graphics.DrawCurve(Pens.Red, curve2)
            End If 
            e.Graphics.DrawRectangle(Pens.Blue, bounds)
        End Sub 'OnPaint
        
        ' Handle the QueryAccessibilityHelp event.
        Private Sub ChartControl_QueryAccessibilityHelp(sender As Object, _
                           e As System.Windows.Forms.QueryAccessibilityHelpEventArgs) Handles MyBase.QueryAccessibilityHelp
            e.HelpString = "Displays chart data"
        End Sub 

        ' Handle the Click event for the chart. 
        ' Toggle the selection of whatever legend was clicked.     
        Private Sub ChartControl_Click(sender As Object, e As System.EventArgs) Handles MyBase.Click

            Dim pt As Point = Me.PointToClient(Control.MousePosition)
            If legend1.Bounds.Contains(pt) Then
                legend1.Selected = Not legend1.Selected
            Else
                If legend2.Bounds.Contains(pt) Then
                    legend2.Selected = Not legend2.Selected
                End If
            End If
        End Sub 'ChartControl_Click

        ' Get an array of the CurveLengends used in the Chart.
        Public ReadOnly Property Legends() As CurveLegend()
            Get
                Return New CurveLegend() {legend1, legend2}
            End Get
        End Property
        
        Protected Sub ExposeAccessibilityNotifyClients(ByVal accEvent As AccessibleEvents, ByVal childID As Integer)
            AccessibilityNotifyClients(accEvent, childID) 
        End Sub

        ' 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

        ' Inner Class that represents a legend for a curve in the chart.
        Public Class CurveLegend
            Private m_name As String
            Private chart As ChartControl
            Private accObj As CurveLegendAccessibleObject
            Private m_selected As Boolean = True
            Private m_location As Point
            
            Public Sub New(chart As ChartControl, name As String)
                Me.chart = chart
                Me.m_name = name
            End Sub 'New

            ' Gets the accessibility object for the curve legend.            
            Public ReadOnly Property AccessibilityObject() As AccessibleObject
                Get
                    If accObj Is Nothing Then
                        accObj = New CurveLegendAccessibleObject(Me)
                    End If
                    Return accObj
                End Get
            End Property
            
            ' Gets the bounds for the curve legend.            
            Public ReadOnly Property Bounds() As Rectangle
                Get
                    Return New Rectangle(Location, Size)
                End Get
            End Property

            ' Gets or sets the location for the curve legend.            
            Public Property Location() As Point
                Get
                    Return m_location
                End Get
                Set
                    m_location = value
                    chart.Invalidate()

                    ' Notifies the chart of the location change. This is used for
                    ' the accessibility information. AccessibleEvents.LocationChange
                    ' tells the chart the reason for the notification.
                    chart.ExposeAccessibilityNotifyClients(AccessibleEvents.LocationChange, _
                            CType(AccessibilityObject, CurveLegendAccessibleObject).ID)
                End Set
            End Property
            
            ' Gets or sets the Name for the curve legend.            
            Public Property Name() As String
                Get
                    Return m_name
                End Get
                Set
                    If m_name <> value Then
                        m_name = value
                        chart.Invalidate()

                        ' Notifies the chart of the name change. This is used for
                        ' the accessibility information. AccessibleEvents.NameChange
                        ' tells the chart the reason for the notification. 
                        chart.ExposeAccessibilityNotifyClients(AccessibleEvents.NameChange, _
                                CType(AccessibilityObject, CurveLegendAccessibleObject).ID)
                    End If
                End Set
            End Property
            
            ' Gets or sets the Selected state for the curve legend.            
            Public Property Selected() As Boolean
                Get
                    Return m_selected
                End Get
                Set
                    If m_selected <> value Then
                        m_selected = value
                        chart.Invalidate()

                        ' Notifies the chart of the selection value change. This is used for
                        ' the accessibility information. The AccessibleEvents value varies
                        ' on whether the selection is true (AccessibleEvents.SelectionAdd) or 
                        ' false (AccessibleEvents.SelectionRemove). 
                        If m_selected Then
                            chart.ExposeAccessibilityNotifyClients(AccessibleEvents.SelectionAdd, _
                                    CType(AccessibilityObject, CurveLegendAccessibleObject).ID) 
                        Else
                            chart.ExposeAccessibilityNotifyClients(AccessibleEvents.SelectionRemove, _
                                    CType(AccessibilityObject, CurveLegendAccessibleObject).ID) 
                        End If
                    End If
                End Set
            End Property
            
            ' Gets the Size for the curve legend.            
            Public ReadOnly Property Size() As Size
                Get
                    Dim legendHeight As Integer = chart.Font.Height + 4
                    Dim g As Graphics = chart.CreateGraphics()
                    Dim legendWidth As Integer = CInt(g.MeasureString(Name, chart.Font).Width) + 4
                    
                    Return New Size(legendWidth, legendHeight)
                End Get
            End Property
            
            
            ' 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

        End Class 'CurveLegend

    End Class 'ChartControl

End Namespace 'ChartControlNameSpace
using System;
using System.Drawing;
using System.Windows.Forms;

namespace ChartControl
{
    public class Form1 : System.Windows.Forms.Form
    {
        // Test out the Chart Control.
        private ChartControl chart1;

        [STAThread]
        static void Main() 
        {
            Application.Run(new Form1());
        }

        public Form1() {
            // Create a chart control and add it to the form.
            this.chart1 = new ChartControl();
            this.ClientSize = new System.Drawing.Size(920, 566);

            this.chart1.Location = new System.Drawing.Point(47, 16);
            this.chart1.Size = new System.Drawing.Size(600, 400);

            this.Controls.Add(this.chart1);
        }
    }

    // Declare a chart control that demonstrates accessibility in Windows Forms.
    public class ChartControl : System.Windows.Forms.UserControl
    {
        private CurveLegend legend1;
        private CurveLegend legend2; 

        public ChartControl()
        {
            // The ChartControl draws the chart in the OnPaint override.
            SetStyle(ControlStyles.ResizeRedraw, true);
            SetStyle(ControlStyles.DoubleBuffer, true);
            SetStyle(ControlStyles.AllPaintingInWmPaint, true);

            this.BackColor = System.Drawing.Color.White;
            this.Name = "ChartControl";

            this.Click += new System.EventHandler(this.ChartControl_Click);
            this.QueryAccessibilityHelp += 
                new System.Windows.Forms.QueryAccessibilityHelpEventHandler(
                                        this.ChartControl_QueryAccessibilityHelp);

            // The CurveLengend is not Control-based, it just
            // represents the parts of the legend.
            legend1 = new CurveLegend(this, "A");
            legend1.Location = new Point(20, 30);
            legend2 = new CurveLegend(this, "B");        
            legend2.Location = new Point(20, 50);
        }

        // Overridden to return the custom AccessibleObject 
        // for the entire chart.
        protected override AccessibleObject CreateAccessibilityInstance() 
        {            
            return new ChartControlAccessibleObject(this);
        }

        protected override void OnPaint(PaintEventArgs e) 
        {
            // The ChartControl draws the chart in the OnPaint override.
            base.OnPaint(e);

            Rectangle bounds = this.ClientRectangle;
            int border = 5;

            // Draws the legends first.
            StringFormat format = new StringFormat();
            format.Alignment = StringAlignment.Center;
            format.LineAlignment = StringAlignment.Center;
            
            if (legend1 != null) {
                if (legend1.Selected) {
                    e.Graphics.FillRectangle(new SolidBrush(Color.Blue), legend1.Bounds);
                } else {
                    e.Graphics.DrawRectangle(Pens.Blue, legend1.Bounds);
                }

                e.Graphics.DrawString(legend1.Name, this.Font, Brushes.Black, legend1.Bounds, format);                
            }
            if (legend2 != null) {
                if (legend2.Selected) {
                    e.Graphics.FillRectangle(new SolidBrush(Color.Red), legend2.Bounds);
                } else {
                    e.Graphics.DrawRectangle(Pens.Red, legend2.Bounds);
                }
                e.Graphics.DrawString(legend2.Name, this.Font, Brushes.Black, legend2.Bounds, format);
            }            

            // Charts out the actual curves that represent data in the Chart.
            bounds.Inflate(-border, -border);
            Point[] curve1 = new Point[] {new Point(bounds.Left, bounds.Bottom),
                            new Point(bounds.Left + bounds.Width / 3, bounds.Top + bounds.Height / 5),
                            new Point(bounds.Right - bounds.Width / 3, (bounds.Top + bounds.Bottom) / 2),
                            new Point(bounds.Right, bounds.Top)};

            Point[] curve2 = new Point[] {new Point(bounds.Left, bounds.Bottom - bounds.Height / 3),
                            new Point(bounds.Left + bounds.Width / 3, bounds.Top + bounds.Height / 5),
                            new Point(bounds.Right - bounds.Width / 3, (bounds.Top + bounds.Bottom) / 2),
                            new Point(bounds.Right, bounds.Top + bounds.Height / 2)};

            // Draws the actual curve only if it is selected.
            if (legend1.Selected) e.Graphics.DrawCurve(Pens.Blue, curve1);
            if (legend2.Selected) e.Graphics.DrawCurve(Pens.Red, curve2);

            e.Graphics.DrawRectangle(Pens.Blue, bounds);            
        }

        // Handles the QueryAccessibilityHelp event.
        private void ChartControl_QueryAccessibilityHelp(object sender, 
                                    System.Windows.Forms.QueryAccessibilityHelpEventArgs e)
        {            
            e.HelpString = "Displays chart data";
        }          

        // Handles the Click event for the chart. 
        // Toggles the selection of whatever legend was clicked on
        private void ChartControl_Click(object sender, System.EventArgs e)
        {
            Point pt = this.PointToClient(Control.MousePosition);
            if (legend1.Bounds.Contains(pt)) {
                legend1.Selected = !legend1.Selected;

            } else if (legend2.Bounds.Contains(pt)) {
                legend2.Selected = !legend2.Selected;
            }
        }

        // Gets an array of CurveLengends used in the Chart.
        public CurveLegend[] Legends
        {   
            get {                
                return new CurveLegend[] { legend1, legend2 };
            }            
        }                

        // 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;                        
                    }
                }            
            }
        }

        // Inner Class that represents a legend for a curve in the chart.
        public class CurveLegend 
        {
            private string name;
            private ChartControl chart;
            private CurveLegendAccessibleObject accObj;
            private bool selected = true;
            private Point location;

            public CurveLegend(ChartControl chart, string name) 
            {
                this.chart = chart;
                this.name = name;
            }

            // Gets the accessibility object for the curve legend.
            public AccessibleObject AccessibilityObject
            {
                get {
                    if (accObj == null) {
                        accObj = new CurveLegendAccessibleObject(this);
                    }
                    return accObj;
                }
            }
            
            // Gets the bounds for the curve legend.
            public Rectangle Bounds
            {   
                get {
                    return new Rectangle(Location, Size);
                }
            }

            // Gets or sets the location for the curve legend.
            public Point Location
            {   
                get {
                    return location;
                }
                set {
                    location = value;
                    chart.Invalidate();

                    // Notifies the chart of the location change. This is used for
                    // the accessibility information. AccessibleEvents.LocationChange
                    // tells the chart the reason for the notification.

                    chart.AccessibilityNotifyClients(AccessibleEvents.LocationChange, 
                        ((CurveLegendAccessibleObject)AccessibilityObject).ID);
                }
            }            
        
            // Gets or sets the Name for the curve legend.
            public string Name
            {   
                get {
                    return name;
                }
                set {
                    if (name != value) 
                    {
                        name = value;
                        chart.Invalidate();

                        // Notifies the chart of the name change. This is used for
                        // the accessibility information. AccessibleEvents.NameChange
                        // tells the chart the reason for the notification.

                        chart.AccessibilityNotifyClients(AccessibleEvents.NameChange, 
                            ((CurveLegendAccessibleObject)AccessibilityObject).ID);
                    }
                }
            }

            // Gets or sets the Selected state for the curve legend.
            public bool Selected
            {   
                get {
                    return selected;
                }
                set {
                    if (selected != value) 
                    {
                        selected = value;
                        chart.Invalidate();

                        // Notifies the chart of the selection value change. This is used for
                        // the accessibility information. The AccessibleEvents value depends upon
                        // if the selection is true (AccessibleEvents.SelectionAdd) or 
                        // false (AccessibleEvents.SelectionRemove).
                        chart.AccessibilityNotifyClients(
                            selected ? AccessibleEvents.SelectionAdd : AccessibleEvents.SelectionRemove, 
                            ((CurveLegendAccessibleObject)AccessibilityObject).ID);
                    }
                }
            }

            // Gets the Size for the curve legend.
            public Size Size
            {   
                get {                    
                    int legendHeight = chart.Font.Height + 4;
                    Graphics g = chart.CreateGraphics();
                    int legendWidth = (int)g.MeasureString(Name, chart.Font).Width + 4;            

                    return new Size(legendWidth, legendHeight);
                }
            }
    
            // Inner class CurveLegendAccessibleObject represents accessible information 
            // associated with the CurveLegend object.
            public class CurveLegendAccessibleObject : AccessibleObject
            {
                private CurveLegend curveLegend;

                public CurveLegendAccessibleObject(CurveLegend curveLegend) : base() 
                {
                    this.curveLegend = curveLegend;                    
                }                

                // Private property that helps get the reference to the parent ChartControl.
                private ChartControlAccessibleObject ChartControl
                {   
                    get {
                        return Parent as ChartControlAccessibleObject;
                    }
                }

                // Internal helper function that returns the ID for this CurveLegend.
                internal int ID
                {
                    get {
                        for(int i = 0; i < ChartControl.GetChildCount(); i++) {
                            if (ChartControl.GetChild(i) == this) {
                                return i;
                            }
                        }
                        return -1;
                    }
                }

                // Gets the Bounds for the CurveLegend. This is used by accessibility programs.
                public override Rectangle Bounds
                {
                    get {                        
                        // The bounds is in screen coordinates.
                        Point loc = curveLegend.Location;
                        return new Rectangle(curveLegend.chart.PointToScreen(loc), curveLegend.Size);
                    }
                }

                // Gets or sets the Name for the CurveLegend. This is used by accessibility programs.
                public override string Name
                {
                    get {
                        return curveLegend.Name;
                    }
                    set {
                        curveLegend.Name = value;                        
                    }
                }

                // Gets the Curve Legend Parent's Accessible object.
                // This is used by accessibility programs.
                public override AccessibleObject Parent
                {
                    get {
                        return curveLegend.chart.AccessibilityObject;
                    }
                }

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

                // Gets the state based on the selection for the CurveLegend. 
                // This is used by accessibility programs.
                public override AccessibleStates State 
                {
                    get {
                        AccessibleStates state = AccessibleStates.Selectable;
                        if (curveLegend.Selected) 
                        {
                            state |= AccessibleStates.Selected;
                        }
                        return state;
                    }
                }

                // Navigates through siblings of this CurveLegend. This is used by accessibility programs.
                public override AccessibleObject Navigate(AccessibleNavigation navdir) 
                {
                    // Uses the internal NavigateFromChild helper function that exists
                    // on ChartControlAccessibleObject.
                    return ChartControl.NavigateFromChild(this, navdir);
                }

                // Selects or unselects this CurveLegend. This is used by accessibility programs.
                public override void Select(AccessibleSelection selection) 
                {
                    // Uses the internal SelectChild helper function that exists
                    // on ChartControlAccessibleObject.
                    ChartControl.SelectChild(this, selection);
                }
            }
        }
    }
}
#using <Accessibility.dll>
#using <System.dll>
#using <System.Windows.Forms.dll>
#using <System.Drawing.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;

// Declare a chart control that demonstrates accessibility in Windows Forms.
public ref class ChartControl: public System::Windows::Forms::UserControl
{
public:
   ref class ChartControlAccessibleObject;

   // forward declaration
   // Inner Class that represents a legend for a curve in the chart.
   ref class CurveLegend
   {

      // Inner class CurveLegendAccessibleObject represents accessible information
      // associated with the CurveLegend object.
   public:
      ref class CurveLegendAccessibleObject: public AccessibleObject
      {
      private:
         CurveLegend^ curveLegend;

      public:
         CurveLegendAccessibleObject( CurveLegend^ curveLegend )
            : AccessibleObject()
         {
            this->curveLegend = curveLegend;
         }


      private:

         property ChartControlAccessibleObject^ ChartControl 
         {

            // Private property that helps get the reference to the parent ChartControl.
            ChartControlAccessibleObject^ get()
            {
               return dynamic_cast<ChartControlAccessibleObject^>(Parent);
            }

         }

      internal:

         property int ID 
         {

            // Internal helper function that returns the ID for this CurveLegend.
            int get()
            {
               for ( int i = 0; i < ChartControl->GetChildCount(); i++ )
               {
                  if ( ChartControl->GetChild( i ) == this )
                  {
                     return i;
                  }

               }
               return  -1;
            }

         }

      public:

         property Rectangle Bounds 
         {

            // Gets the Bounds for the CurveLegend. This is used by accessibility programs.
            virtual Rectangle get() override
            {
               
               // The bounds is in screen coordinates.
               Point loc = curveLegend->Location;
               return Rectangle(curveLegend->chart->PointToScreen( loc ),curveLegend->Size);
            }

         }

         property String^ Name 
         {

            // Gets or sets the Name for the CurveLegend. This is used by accessibility programs.
            virtual String^ get() override
            {
               return curveLegend->Name;
            }

            virtual void set( String^ value ) override
            {
               curveLegend->Name = value;
            }

         }

         property AccessibleObject^ Parent 
         {

            // Gets the Curve Legend Parent's Accessible object.
            // This is used by accessibility programs.
            virtual AccessibleObject^ get() override
            {
               return curveLegend->chart->AccessibilityObject;
            }

         }

         property System::Windows::Forms::AccessibleRole Role 
         {

            // Gets the role for the CurveLegend. This is used by accessibility programs.
            virtual System::Windows::Forms::AccessibleRole get() override
            {
               return ::AccessibleRole::StaticText;
            }

         }

         property AccessibleStates State 
         {

            // Gets the state based on the selection for the CurveLegend.
            // This is used by accessibility programs.
            virtual AccessibleStates get() override
            {
               AccessibleStates state = AccessibleStates::Selectable;
               if ( curveLegend->Selected )
               {
                  state = static_cast<AccessibleStates>(state | AccessibleStates::Selected);
               }

               return state;
            }

         }

         // Navigates through siblings of this CurveLegend. This is used by accessibility programs.
         virtual AccessibleObject^ Navigate( AccessibleNavigation navdir ) override
         {
            
            // Uses the internal NavigateFromChild helper function that exists
            // on ChartControlAccessibleObject.
            return ChartControl->NavigateFromChild( this, navdir );
         }


         // Selects or unselects this CurveLegend. This is used by accessibility programs.
         virtual void Select( AccessibleSelection selection ) override
         {
            
            // Uses the internal SelectChild helper function that exists
            // on ChartControlAccessibleObject.
            ChartControl->SelectChild( this, selection );
         }

      };


   private:

      // class CurveLgendAccessibleObject
      String^ name;
      ChartControl^ chart;
      CurveLegendAccessibleObject^ accObj;
      bool selected;
      Point location;

   public:
      CurveLegend( ChartControl^ chart, String^ name )
      {
         this->chart = chart;
         this->name = name;
         selected = true;
      }


      property AccessibleObject^ AccessibilityObject 
      {

         // Gets the accessibility object for the curve legend.
         AccessibleObject^ get()
         {
            if ( accObj == nullptr )
            {
               accObj = gcnew CurveLegendAccessibleObject( this );
            }

            return accObj;
         }

      }

      property Rectangle Bounds 
      {

         // Gets the bounds for the curve legend.
         Rectangle get()
         {
            return Rectangle(Location,Size);
         }

      }

      property Point Location 
      {

         // Gets or sets the location for the curve legend.
         Point get()
         {
            return location;
         }

         void set( Point value )
         {
            location = value;
            chart->Invalidate();
            
            // Notifies the chart of the location change. This is used for
            // the accessibility information. AccessibleEvents::LocationChange
            // tells the chart the reason for the notification.
            chart->AccessibilityNotifyClients( AccessibleEvents::LocationChange, (dynamic_cast<CurveLegendAccessibleObject^>(AccessibilityObject))->ID );
         }

      }

      property String^ Name 
      {

         // Gets or sets the Name for the curve legend.
         String^ get()
         {
            return name;
         }

         void set( String^ value )
         {
            if ( name != value )
            {
               name = value;
               chart->Invalidate();
               
               // Notifies the chart of the name change. This is used for
               // the accessibility information. AccessibleEvents::NameChange
               // tells the chart the reason for the notification.
               chart->AccessibilityNotifyClients( AccessibleEvents::NameChange, (dynamic_cast<CurveLegendAccessibleObject^>(AccessibilityObject))->ID );
            }
         }

      }

      property bool Selected 
      {

         // Gets or sets the Selected state for the curve legend.
         bool get()
         {
            return selected;
         }

         void set( bool value )
         {
            if ( selected != value )
            {
               selected = value;
               chart->Invalidate();
               
               // Notifies the chart of the selection value change. This is used for
               // the accessibility information. The AccessibleEvents value depends upon
               // if the selection is true (AccessibleEvents::SelectionAdd) or
               // false (AccessibleEvents::SelectionRemove).
               chart->AccessibilityNotifyClients( selected ? AccessibleEvents::SelectionAdd : AccessibleEvents::SelectionRemove, (dynamic_cast<CurveLegendAccessibleObject^>(AccessibilityObject))->ID );
            }
         }

      }

      property System::Drawing::Size Size 
      {

         // Gets the Size for the curve legend.
         System::Drawing::Size get()
         {
            int legendHeight = chart->Font->Height + 4;
            Graphics^ g = chart->CreateGraphics();
            int legendWidth = (int)g->MeasureString( Name, chart->Font ).Width + 4;
            return System::Drawing::Size( legendWidth, legendHeight );
         }

      }

   };


private:

   // class CurveLegend
   CurveLegend^ legend1;
   CurveLegend^ legend2;

public:
   ChartControl()
   {
      
      // The ChartControl draws the chart in the OnPaint .
      SetStyle( ControlStyles::ResizeRedraw, true );
      SetStyle( ControlStyles::DoubleBuffer, true );
      SetStyle( ControlStyles::AllPaintingInWmPaint, true );
      this->BackColor = System::Drawing::Color::White;
      this->Name = "ChartControl";
      this->Click += gcnew System::EventHandler( this, &ChartControl::ChartControl_Click );
      this->QueryAccessibilityHelp += gcnew System::Windows::Forms::QueryAccessibilityHelpEventHandler( this, &ChartControl::ChartControl_QueryAccessibilityHelp );
      
      // The CurveLengend is not Control-based, it just
      // represents the parts of the legend.
      legend1 = gcnew CurveLegend( this,"A" );
      legend1->Location = Point(20,30);
      legend2 = gcnew CurveLegend( this,"B" );
      legend2->Location = Point(20,50);
   }



protected:
   // Overridden to return the custom AccessibleObject
   // for the entire chart.
   virtual AccessibleObject^ CreateAccessibilityInstance() override
   {
      return gcnew ChartControlAccessibleObject( this );
   }

   virtual void OnPaint( PaintEventArgs^ e ) override
   {
      
      // The ChartControl draws the chart in the OnPaint .
      System::Windows::Forms::UserControl::OnPaint( e );
      Rectangle bounds = this->ClientRectangle;
      int border = 5;
      
      // Draws the legends first.
      StringFormat^ format = gcnew StringFormat;
      format->Alignment = StringAlignment::Center;
      format->LineAlignment = StringAlignment::Center;
      if ( legend1 != nullptr )
      {
         if ( legend1->Selected )
         {
            e->Graphics->FillRectangle( gcnew SolidBrush( Color::Blue ), legend1->Bounds );
         }
         else
         {
            e->Graphics->DrawRectangle( Pens::Blue, legend1->Bounds );
         }

         e->Graphics->DrawString( legend1->Name, this->Font, Brushes::Black, legend1->Bounds, format );
      }

      if ( legend2 != nullptr )
      {
         if ( legend2->Selected )
         {
            e->Graphics->FillRectangle( gcnew SolidBrush( Color::Red ), legend2->Bounds );
         }
         else
         {
            e->Graphics->DrawRectangle( Pens::Red, legend2->Bounds );
         }

         e->Graphics->DrawString( legend2->Name, this->Font, Brushes::Black, legend2->Bounds, format );
      }

      
      // Charts out the actual curves that represent data in the Chart.
      bounds.Inflate(  -border,  -border );
      array<Point>^ temp1 = {Point(bounds.Left,bounds.Bottom),Point(bounds.Left + bounds.Width / 3,bounds.Top + bounds.Height / 5),Point(bounds.Right - bounds.Width / 3,(bounds.Top + bounds.Bottom) / 2),Point(bounds.Right,bounds.Top)};
      array<Point>^curve1 = temp1;
      array<Point>^ temp2 = {Point(bounds.Left,bounds.Bottom - bounds.Height / 3),Point(bounds.Left + bounds.Width / 3,bounds.Top + bounds.Height / 5),Point(bounds.Right - bounds.Width / 3,(bounds.Top + bounds.Bottom) / 2),Point(bounds.Right,bounds.Top + bounds.Height / 2)};
      array<Point>^curve2 = temp2;
      
      // Draws the actual curve only if it is selected.
      if ( legend1->Selected )
            e->Graphics->DrawCurve( Pens::Blue, curve1 );

      if ( legend2->Selected )
            e->Graphics->DrawCurve( Pens::Red, curve2 );

      e->Graphics->DrawRectangle( Pens::Blue, bounds );
   }

   // Handles the QueryAccessibilityHelp event.
   void ChartControl_QueryAccessibilityHelp( Object^ /*sender*/, System::Windows::Forms::QueryAccessibilityHelpEventArgs^ e )
   {
      e->HelpString = "Displays chart data";
   }

   // Handles the Click event for the chart.
   // Toggles the selection of whatever legend was clicked on
   void ChartControl_Click( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      Point pt = this->PointToClient( Control::MousePosition );
      if ( legend1->Bounds.Contains( pt ) )
      {
         legend1->Selected =  !legend1->Selected;
      }
      else
      if ( legend2->Bounds.Contains( pt ) )
      {
         legend2->Selected =  !legend2->Selected;
      }
   }


public:

   property array<CurveLegend^>^ Legends 
   {

      // Gets an array of CurveLengends used in the Chart.
      array<CurveLegend^>^ get()
      {
         array<CurveLegend^>^temp3 = {legend1,legend2};
         return temp3;
      }

   }

   // Inner class ChartControlAccessibleObject represents accessible information associated with the ChartControl.
   // The ChartControlAccessibleObject is returned in the ChartControl::CreateAccessibilityInstance .
   ref class ChartControlAccessibleObject: public ControlAccessibleObject
   {
   private:
      ChartControl^ chartControl;

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


      property System::Windows::Forms::AccessibleRole Role 
      {

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

      }

      property AccessibleStates State 
      {

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

      }

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


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

         return nullptr;
      }


   internal:

      // 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.
      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 nullptr;
      }


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

   };

   // class ChartControlAccessibleObject
};


// class ChartControl
public ref class Form1: public System::Windows::Forms::Form
{
private:

   // Test out the Chart Control.
   ChartControl^ chart1;

public:
   Form1()
   {
      
      // Create a chart control and add it to the form.
      this->chart1 = gcnew ChartControl;
      this->ClientSize = System::Drawing::Size( 920, 566 );
      this->chart1->Location = System::Drawing::Point( 47, 16 );
      this->chart1->Size = System::Drawing::Size( 600, 400 );
      this->Controls->Add( this->chart1 );
   }

};


// class Form1

[STAThread]
int main()
{
   Application::Run( gcnew Form1 );
}
package ChartControl;

import System.*;
import System.Drawing.*;
import System.Windows.Forms.*;

public class Form1 extends System.Windows.Forms.Form
{
    // Test out the Chart Control.
    private ChartControl chart1;

    /** @attribute STAThread()
     */
    public static void main(String[] args)
    {
        Application.Run(new Form1());
    } //main

    public Form1()
    {
        // Create a chart control and add it to the form.
        this.chart1 = new ChartControl();
        this.set_ClientSize(new System.Drawing.Size(920, 566));

        this.chart1.set_Location(new System.Drawing.Point(47, 16));
        this.chart1.set_Size(new System.Drawing.Size(600, 400));
        this.get_Controls().Add(this.chart1);
    } //Form1
} //Form1

// Declare a chart control that demonstrates accessibility in Windows Forms.
public class ChartControl extends System.Windows.Forms.UserControl
{
    private CurveLegend legend1;
    private CurveLegend legend2;

    public ChartControl()
    {
        // The ChartControl draws the chart in the OnPaint override.
        SetStyle(ControlStyles.ResizeRedraw, true);
        SetStyle(ControlStyles.DoubleBuffer, true);
        SetStyle(ControlStyles.AllPaintingInWmPaint, true);

        this.set_BackColor(System.Drawing.Color.get_White());
        this.set_Name("ChartControl");
        this.add_Click(new System.EventHandler(this.ChartControl_Click));
        this.add_QueryAccessibilityHelp(new System.Windows.Forms.
            QueryAccessibilityHelpEventHandler(
            this.ChartControl_QueryAccessibilityHelp));

        // The CurveLengend is not Control-based, it just
        // represents the parts of the legend.
        legend1 = new CurveLegend(this, "A");
        legend1.set_Location(new Point(20, 30));
        legend2 = new CurveLegend(this, "B");
        legend2.set_Location(new Point(20, 50));
    } //ChartControl

    // Overridden to return the custom AccessibleObject 
    // for the entire chart.
    protected AccessibleObject CreateAccessibilityInstance()
    {
        return new ChartControlAccessibleObject(this);
    } //CreateAccessibilityInstance

    protected void OnPaint(PaintEventArgs e)
    {
        // The ChartControl draws the chart in the OnPaint override.
        super.OnPaint(e);
        Rectangle bounds = this.get_ClientRectangle();
        int border = 5;
        // Draws the legends first.
        StringFormat format = new StringFormat();
        format.set_Alignment(StringAlignment.Center);
        format.set_LineAlignment(StringAlignment.Center);

        if (legend1 != null) {
            if (legend1.get_Selected()) {
                e.get_Graphics().FillRectangle(new SolidBrush(Color.get_Blue()),
                    legend1.get_Bounds());
            }
            else {
                e.get_Graphics().DrawRectangle(Pens.get_Blue(), 
                    legend1.get_Bounds());
            }
            e.get_Graphics().DrawString(legend1.get_Name(), this.get_Font(), 
                Brushes.get_Black(), 
                RectangleF.op_Implicit(legend1.get_Bounds()), format);
        }
        if (legend2 != null) {
            if (legend2.get_Selected()) {
                e.get_Graphics().FillRectangle(new SolidBrush(Color.get_Red()), 
                    legend2.get_Bounds());
            }
            else {
                e.get_Graphics().DrawRectangle(Pens.get_Red(),
                    legend2.get_Bounds());
            }
            e.get_Graphics().DrawString(legend2.get_Name(), this.get_Font(),
                Brushes.get_Black(), 
                RectangleF.op_Implicit(legend2.get_Bounds()), format);
        }

        // Charts out the actual curves that represent data in the Chart.
        bounds.Inflate(-border, -border);
        Point curve1[] = new Point[] { new Point(bounds.get_Left(), 
            bounds.get_Bottom()), 
            new Point(bounds.get_Left() + bounds.get_Width() / 3,
            bounds.get_Top() + bounds.get_Height() / 5), 
            new Point(bounds.get_Right() - bounds.get_Width() / 3, 
            (bounds.get_Top() + bounds.get_Bottom()) / 2), 
            new Point(bounds.get_Right(), bounds.get_Top()) };

        Point curve2[] = new Point[] { new Point(bounds.get_Left(), 
            bounds.get_Bottom() - bounds.get_Height() / 3), 
            new Point(bounds.get_Left() + bounds.get_Width() / 3, 
            bounds.get_Top() + bounds.get_Height() / 5), 
            new Point(bounds.get_Right() - bounds.get_Width() / 3, 
            (bounds.get_Top() + bounds.get_Bottom()) / 2), 
            new Point(bounds.get_Right(), 
            bounds.get_Top() + bounds.get_Height() / 2) };

        // Draws the actual curve only if it is selected.
        if (legend1.get_Selected()) {
            e.get_Graphics().DrawCurve(Pens.get_Blue(), curve1);
        }
        if (legend2.get_Selected()) {
            e.get_Graphics().DrawCurve(Pens.get_Red(), curve2);
        }
        e.get_Graphics().DrawRectangle(Pens.get_Blue(), bounds);
    } //OnPaint

    // Handles the QueryAccessibilityHelp event.
    private void ChartControl_QueryAccessibilityHelp(Object sender, 
        System.Windows.Forms.QueryAccessibilityHelpEventArgs e)
    {
        e.set_HelpString("Displays chart data");
    } //ChartControl_QueryAccessibilityHelp

    // Handles the Click event for the chart. 
    // Toggles the selection of whatever legend was clicked on
    private void ChartControl_Click(Object sender, System.EventArgs e)
    {
        Point pt = this.PointToClient(Control.get_MousePosition());
        if (legend1.get_Bounds().Contains(pt)) {
            legend1.set_Selected(!(legend1.get_Selected()));
        }
        else {
            if (legend2.get_Bounds().Contains(pt)) {
                legend2.set_Selected(!(legend2.get_Selected()));
            }
        }
    } //ChartControl_Click

    // Gets an array of CurveLengends used in the Chart.
    /** @property 
     */
    public CurveLegend[] get_Legends()
    {
        return new CurveLegend[] { legend1, legend2 };
    } //get_Legends

    // Inner class ChartControlAccessibleObject represents accessible 
    // information associated with the ChartControl.
    // The ChartControlAccessibleObject is returned in the 
    // ChartControl.CreateAccessibilityInstance override.
    public static class ChartControlAccessibleObject 
        extends ControlAccessibleObject
    {
        private ChartControl chartControl;

        public ChartControlAccessibleObject(ChartControl ctrl)
        {
            super(ctrl);
            chartControl = ctrl;
        } //ChartControlAccessibleObject

        // Gets the role for the Chart. This is used by accessibility programs.
        /** @property 
         */
        public AccessibleRole get_Role()
        {
            return AccessibleRole.Chart;
        } //get_Role

        // Gets the state for the Chart. This is used by accessibility programs.
        /** @property 
         */
        public AccessibleStates get_State()
        {
            return AccessibleStates.ReadOnly;
        } //get_State

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

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

        // 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.
        AccessibleObject NavigateFromChild(
            CurveLegend.CurveLegendAccessibleObject child, 
            AccessibleNavigation navDir)
        {
            if (navDir.Equals(AccessibleNavigation.Down) 
                || navDir.Equals(AccessibleNavigation.Next)) {
                return GetChild(child.get_ID() + 1);
            }
            else {
                if (navDir.Equals(AccessibleNavigation.Up) 
                    || navDir.Equals(AccessibleNavigation.Previous)) {
                    return GetChild(child.get_ID() - 1);
                }
            }
            return null;
        } //NavigateFromChild

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

            // Determine which selection action should occur, based on the
            // AccessibleSelection value.
            if (Convert.ToInt32(selection & AccessibleSelection.TakeSelection)
                != 0) {
                for (int i = 0; i < chartControl.get_Legends().get_Length(); 
                    i++) {
                    if (i == childID) {
                        ((CurveLegend)chartControl.get_Legends().get_Item(i)).
                            set_Selected(true);
                    }
                    else {
                        ((CurveLegend)chartControl.get_Legends().get_Item(i)).
                            set_Selected(false);
                    }
                }

                // AccessibleSelection.AddSelection means that the CurveLegend 
                // will be selected.
                if (Convert.ToInt32(selection & AccessibleSelection.AddSelection)
                    != 0) {
                    ((CurveLegend)chartControl.get_Legends().get_Item(childID)).
                        set_Selected(true);
                }

                // AccessibleSelection.AddSelection means that the CurveLegend 
                // will be unselected.
                if (Convert.ToInt32(selection & 
                    AccessibleSelection.RemoveSelection) != 0) {
                    ((CurveLegend)chartControl.get_Legends().get_Item(childID)).
                        set_Selected(false);
                }
            }
        } //SelectChild
    } //ChartControlAccessibleObject

    // Inner Class that represents a legend for a curve in the chart.
    public static class CurveLegend
    {
        private String name;
        private ChartControl chart;
        private CurveLegendAccessibleObject accObj;
        private boolean selected = true;
        private Point location;

        public CurveLegend(ChartControl chart, String name)
        {
            this.chart = chart;
            this.name = name;
        } //CurveLegend

        // Gets the accessibility object for the curve legend.
        /** @property 
         */
        public AccessibleObject get_AccessibilityObject()
        {
            if (accObj == null) {
                accObj = new CurveLegendAccessibleObject(this);
            }
            return accObj;
        } //get_AccessibilityObject

        // Gets the bounds for the curve legend.
        /** @property 
         */
        public Rectangle get_Bounds()
        {
            return new Rectangle(get_Location(), get_Size());
        } //get_Bounds

        // Gets or sets the location for the curve legend.
        /** @property 
         */
        public Point get_Location()
        {
            return location;
        } //get_Location

        /** @property 
         */
        public void set_Location(Point value)
        {
            location = value;
            chart.Invalidate();
            // Notifies the chart of the location change. This is used for
            // the accessibility information. AccessibleEvents.LocationChange
            // tells the chart the reason for the notification.
            chart.AccessibilityNotifyClients(AccessibleEvents.LocationChange, 
                ((CurveLegendAccessibleObject)get_AccessibilityObject()).
                get_ID());
        } //set_Location

        // Gets or sets the Name for the curve legend.
        /** @property 
         */
        public String get_Name()
        {
            return name;
        } //get_Name

        /** @property 
         */
        public void set_Name(String value)
        {
            if (!name.Equals(value)) {
                name = value;
                chart.Invalidate();

                // Notifies the chart of the name change. This is used for
                // the accessibility information. AccessibleEvents.NameChange
                // tells the chart the reason for the notification.
                chart.AccessibilityNotifyClients(AccessibleEvents.NameChange,
                    ((CurveLegendAccessibleObject)get_AccessibilityObject()).
                    get_ID());
            }
        } //set_Name

        // Gets or sets the Selected state for the curve legend.
        /** @property 
         */
        public boolean get_Selected()
        {
            return selected;
        } //get_Selected

        /** @property 
         */
        public void set_Selected(boolean value)
        {
            if (selected != value) {
                selected = value;
                chart.Invalidate();

                // Notifies the chart of the selection value change. 
                // This is used for the accessibility information. 
                // The AccessibleEvents value depends upon
                // if the selection is true (AccessibleEvents.SelectionAdd) or 
                // false (AccessibleEvents.SelectionRemove).
                chart.AccessibilityNotifyClients(selected ? 
                    AccessibleEvents.SelectionAdd : 
                    AccessibleEvents.SelectionRemove, 
                    ((CurveLegendAccessibleObject)get_AccessibilityObject()).
                    get_ID());
            }
        } //set_Selected

        // Gets the Size for the curve legend.
        /** @property 
         */
        public Size get_Size()
        {
            int legendHeight = chart.get_Font().get_Height() + 4;
            Graphics g = chart.CreateGraphics();
            int legendWidth = (int)(g.MeasureString(get_Name(), 
                chart.get_Font()).get_Width()) + 4;

            return new Size(legendWidth, legendHeight);
        } //get_Size

        // Inner class CurveLegendAccessibleObject represents accessible 
        // information associated with the CurveLegend object.
        public static class CurveLegendAccessibleObject extends AccessibleObject
        {
            private CurveLegend curveLegend;

            public CurveLegendAccessibleObject(CurveLegend curveLegend)
            {
                this.curveLegend = curveLegend;
            } //CurveLegendAccessibleObject

            // Private property that helps get the reference to the parent 
            // ChartControl.
            /** @property 
             */
            private ChartControlAccessibleObject get_ChartControl()
            {
                return (ChartControlAccessibleObject)get_Parent();
            } //get_ChartControl

            // Internal helper function that returns the ID for this CurveLegend.
            /** @property 
             */
            int get_ID()
            {
                for (int i = 0; i < get_ChartControl().GetChildCount(); i++) {
                    if (get_ChartControl().GetChild(i).Equals(this)) {
                        return i;
                    }
                }
                return -1;
            } //get_ID

            // Gets the Bounds for the CurveLegend. 
            // This is used by accessibility programs.
            /** @property 
             */
            public Rectangle get_Bounds()
            {
                // The bounds is in screen coordinates.
                Point loc = curveLegend.get_Location();
                return new Rectangle(curveLegend.chart.PointToScreen(loc),
                    curveLegend.get_Size());
            } //get_Bounds

            // Gets or sets the Name for the CurveLegend. 
            // This is used by accessibility programs.
            /** @property 
             */
            public String get_Name()
            {
                return curveLegend.get_Name();
            } //get_Name

            /** @property 
             */
            public void set_Name(String value)
            {
                curveLegend.set_Name(value);
            } //set_Name

            // Gets the Curve Legend Parent's Accessible object.
            // This is used by accessibility programs.
            /** @property 
             */
            public AccessibleObject get_Parent()
            {
                return curveLegend.chart.get_AccessibilityObject();
            } //get_Parent

            // Gets the role for the CurveLegend. 
            // This is used by accessibility programs.
            /** @property 
             */
            public AccessibleRole get_Role()
            {
                return AccessibleRole.StaticText;
            } //get_Role

            // Gets the state based on the selection for the CurveLegend. 
            // This is used by accessibility programs.
            /** @property 
             */
            public AccessibleStates get_State()
            {
                AccessibleStates state = AccessibleStates.Selectable;
                if (curveLegend.get_Selected()) {
                    state = state | AccessibleStates.Selected;
                }
                return state;
            } //get_State

            // Navigates through siblings of this CurveLegend. 
            // This is used by accessibility programs.
            public AccessibleObject Navigate(AccessibleNavigation navDir)
            {
                // Uses the internal NavigateFromChild helper function 
                // that exists on ChartControlAccessibleObject.
                return get_ChartControl().NavigateFromChild(this, navDir);
            } //Navigate

            // Selects or unselects this CurveLegend. 
            // This is used by accessibility programs.
            public void Select(AccessibleSelection selection)
            {
                // Uses the internal SelectChild helper function that exists
                // on ChartControlAccessibleObject.
                get_ChartControl().SelectChild(this, selection);
            } //Select
        } //CurveLegendAccessibleObject
    } //CurveLegend 
} //ChartControl

继承层次结构

System.Object
   System.MarshalByRefObject
     System.Runtime.InteropServices.StandardOleMarshalObject
      System.Windows.Forms.AccessibleObject
         派生类

线程安全

此类型的任何公共静态(Visual Basic 中的 Shared)成员都是线程安全的,但不保证所有实例成员都是线程安全的。

平台

Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition

.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表,请参见系统要求

版本信息

.NET Framework

受以下版本支持:2.0、1.1、1.0

请参见

参考

AccessibleObject 成员
System.Windows.Forms 命名空间