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如何：在 MenuStrip 中显示选项按钮（Windows 窗体）

  • 项目

更新：2007 年 11 月

选项按钮也称作单选按钮，它与复选框很相似，但用户一次只能选中一个。尽管在默认情况下 ToolStripMenuItem 类不提供选项按钮行为，但该类提供复选框行为供自定义，以便为 MenuStrip 控件中的菜单项实现选项按钮行为。

当菜单项的 CheckOnClick 属性为 true 时，用户可以单击该项以切换选中标记的显示。Checked 属性指示项的当前状态。要实现基本选项按钮行为，必须确保在选中一个项时，将以前选中项的 Checked 属性设置为 false。

下面的过程描述如何在继承 ToolStripMenuItem 类的类中实现此功能及附加功能。ToolStripRadioButtonMenuItem 类重写诸如 OnCheckedChanged 和 OnPaint 等成员，以提供选项按钮的选择行为和外观。此外，此类重写 Enabled 属性，这样，除非选中父项，否则将禁用子菜单上的选项。

实现选项按钮选择行为

  1. 将 CheckOnClick 属性初始化为 true 以启用项的选择。

    ' Called by all constructors to initialize CheckOnClick.
Private Sub Initialize()
    CheckOnClick = True
End Sub

    // Called by all constructors to initialize CheckOnClick.
private void Initialize()
{
    CheckOnClick = true;
}

  2. 选定新项后，重写 OnCheckedChanged 方法以清除以前选定项的选择。

    Protected Overrides Sub OnCheckedChanged(ByVal e As EventArgs)

    MyBase.OnCheckedChanged(e)

    ' If this item is no longer in the checked state or if its 
    ' parent has not yet been initialized, do nothing.
    If Not Checked OrElse Me.Parent Is Nothing Then Return

    ' Clear the checked state for all siblings. 
    For Each item As ToolStripItem In Parent.Items

        Dim radioItem As ToolStripRadioButtonMenuItem = _
            TryCast(item, ToolStripRadioButtonMenuItem)
        If radioItem IsNot Nothing AndAlso _
            radioItem IsNot Me AndAlso _
            radioItem.Checked Then

            radioItem.Checked = False

            ' Only one item can be selected at a time, 
            ' so there is no need to continue.
            Return

        End If
    Next

End Sub

    protected override void OnCheckedChanged(EventArgs e)
{
    base.OnCheckedChanged(e);

    // If this item is no longer in the checked state or if its 
    // parent has not yet been initialized, do nothing.
    if (!Checked || this.Parent == null) return;

    // Clear the checked state for all siblings. 
    foreach (ToolStripItem item in Parent.Items)
    {
        ToolStripRadioButtonMenuItem radioItem =
            item as ToolStripRadioButtonMenuItem;
        if (radioItem != null && radioItem != this && radioItem.Checked)
        {
            radioItem.Checked = false;

            // Only one item can be selected at a time, 
            // so there is no need to continue.
            return;
        }
    }
}

  3. 重写 OnClick 方法，以确保单击已选定的项时不会将选择清除。

    Protected Overrides Sub OnClick(ByVal e As EventArgs)

    ' If the item is already in the checked state, do not call 
    ' the base method, which would toggle the value. 
    If Checked Then Return

    MyBase.OnClick(e)
End Sub

    protected override void OnClick(EventArgs e)
{
    // If the item is already in the checked state, do not call 
    // the base method, which would toggle the value. 
    if (Checked) return;

    base.OnClick(e);
}

修改选项按钮项的外观

  1. 重写 OnPaint 方法，以使用 RadioButtonRenderer 类通过选项按钮来替换默认选中标记。

    ' Let the item paint itself, and then paint the RadioButton
' where the check mark is normally displayed.
Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)

    If Image IsNot Nothing Then
        ' If the client sets the Image property, the selection behavior
        ' remains unchanged, but the RadioButton is not displayed and the
        ' selection is indicated only by the selection rectangle. 
        MyBase.OnPaint(e)
        Return
    Else
        ' If the Image property is not set, call the base OnPaint method 
        ' with the CheckState property temporarily cleared to prevent
        ' the check mark from being painted.
        Dim currentState As CheckState = Me.CheckState
        Me.CheckState = CheckState.Unchecked
        MyBase.OnPaint(e)
        Me.CheckState = currentState
    End If

    ' Determine the correct state of the RadioButton.
    Dim buttonState As RadioButtonState = RadioButtonState.UncheckedNormal
    If Enabled Then
        If mouseDownState Then
            If Checked Then
                buttonState = RadioButtonState.CheckedPressed
            Else
                buttonState = RadioButtonState.UncheckedPressed
            End If
        ElseIf mouseHoverState Then
            If Checked Then
                buttonState = RadioButtonState.CheckedHot
            Else
                buttonState = RadioButtonState.UncheckedHot
            End If
        Else
            If Checked Then buttonState = RadioButtonState.CheckedNormal
        End If
    Else
        If Checked Then
            buttonState = RadioButtonState.CheckedDisabled
        Else
            buttonState = RadioButtonState.UncheckedDisabled
        End If
    End If

    ' Calculate the position at which to display the RadioButton.
    Dim offset As Int32 = CInt((ContentRectangle.Height - _
        RadioButtonRenderer.GetGlyphSize( _
        e.Graphics, buttonState).Height) / 2)
    Dim imageLocation As Point = New Point( _
        ContentRectangle.Location.X + 4, _
        ContentRectangle.Location.Y + offset)

    ' Paint the RadioButton. 
    RadioButtonRenderer.DrawRadioButton( _
        e.Graphics, imageLocation, buttonState)

End Sub

    // Let the item paint itself, and then paint the RadioButton
// where the check mark is normally displayed.
protected override void OnPaint(PaintEventArgs e)
{
    if (Image != null)
    {
        // If the client sets the Image property, the selection behavior
        // remains unchanged, but the RadioButton is not displayed and the
        // selection is indicated only by the selection rectangle. 
        base.OnPaint(e);
        return;
    }
    else
    {
        // If the Image property is not set, call the base OnPaint method 
        // with the CheckState property temporarily cleared to prevent
        // the check mark from being painted.
        CheckState currentState = this.CheckState;
        this.CheckState = CheckState.Unchecked;
        base.OnPaint(e);
        this.CheckState = currentState;
    }

    // Determine the correct state of the RadioButton.
    RadioButtonState buttonState = RadioButtonState.UncheckedNormal;
    if (Enabled)
    {
        if (mouseDownState)
        {
            if (Checked) buttonState = RadioButtonState.CheckedPressed;
            else buttonState = RadioButtonState.UncheckedPressed;
        }
        else if (mouseHoverState)
        {
            if (Checked) buttonState = RadioButtonState.CheckedHot;
            else buttonState = RadioButtonState.UncheckedHot;
        }
        else
        {
            if (Checked) buttonState = RadioButtonState.CheckedNormal;
        }
    }
    else
    {
        if (Checked) buttonState = RadioButtonState.CheckedDisabled;
        else buttonState = RadioButtonState.UncheckedDisabled;
    }

    // Calculate the position at which to display the RadioButton.
    Int32 offset = (ContentRectangle.Height -
        RadioButtonRenderer.GetGlyphSize(
        e.Graphics, buttonState).Height) / 2;
    Point imageLocation = new Point(
        ContentRectangle.Location.X + 4,
        ContentRectangle.Location.Y + offset);

    // Paint the RadioButton. 
    RadioButtonRenderer.DrawRadioButton(
        e.Graphics, imageLocation, buttonState);
}

  2. 重写 OnMouseEnter、OnMouseLeave、OnMouseDown 和 OnMouseUp 方法，以跟踪鼠标状态并确保 OnPaint 方法绘制正确的选项按钮状态。

    Private mouseHoverState As Boolean = False

Protected Overrides Sub OnMouseEnter(ByVal e As EventArgs)
    mouseHoverState = True

    ' Force the item to repaint with the new RadioButton state.
    Invalidate()

    MyBase.OnMouseEnter(e)
End Sub

Protected Overrides Sub OnMouseLeave(ByVal e As EventArgs)
    mouseHoverState = False
    MyBase.OnMouseLeave(e)
End Sub

Private mouseDownState As Boolean = False

Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
    mouseDownState = True

    ' Force the item to repaint with the new RadioButton state.
    Invalidate()

    MyBase.OnMouseDown(e)
End Sub

Protected Overrides Sub OnMouseUp(ByVal e As MouseEventArgs)
    mouseDownState = False
    MyBase.OnMouseUp(e)
End Sub

    private bool mouseHoverState = false;

protected override void OnMouseEnter(EventArgs e)
{
    mouseHoverState = true;

    // Force the item to repaint with the new RadioButton state.
    Invalidate();

    base.OnMouseEnter(e);
}

protected override void OnMouseLeave(EventArgs e)
{
    mouseHoverState = false;
    base.OnMouseLeave(e);
}

private bool mouseDownState = false;

protected override void OnMouseDown(MouseEventArgs e)
{
    mouseDownState = true;

    // Force the item to repaint with the new RadioButton state.
    Invalidate();

    base.OnMouseDown(e);
}

protected override void OnMouseUp(MouseEventArgs e)
{
    mouseDownState = false;
    base.OnMouseUp(e);
}

在未选中父项时禁用子菜单上的选项

  1. 重写 Enabled 属性，以便当项具有 CheckOnClick 值为 true 且 Checked 值为 false 的父项时禁用该项。

    ' Enable the item only if its parent item is in the checked state 
' and its Enabled property has not been explicitly set to false. 
Public Overrides Property Enabled() As Boolean
    Get
        Dim ownerMenuItem As ToolStripMenuItem = _
            TryCast(OwnerItem, ToolStripMenuItem)

        ' Use the base value in design mode to prevent the designer
        ' from setting the base value to the calculated value.
        If Not DesignMode AndAlso ownerMenuItem IsNot Nothing AndAlso _
            ownerMenuItem.CheckOnClick Then
            Return MyBase.Enabled AndAlso ownerMenuItem.Checked
        Else
            Return MyBase.Enabled
        End If
    End Get

    Set(ByVal value As Boolean)
        MyBase.Enabled = value
    End Set
End Property

    // Enable the item only if its parent item is in the checked state 
// and its Enabled property has not been explicitly set to false. 
public override bool Enabled
{
    get
    {
        ToolStripMenuItem ownerMenuItem =
            OwnerItem as ToolStripMenuItem;

        // Use the base value in design mode to prevent the designer
        // from setting the base value to the calculated value.
        if (!DesignMode &&
            ownerMenuItem != null && ownerMenuItem.CheckOnClick)
        {
            return base.Enabled && ownerMenuItem.Checked;
        }
        else return base.Enabled;
    }
    set
    {
        base.Enabled = value;
    }
}

  2. 重写 OnOwnerChanged 方法，以订阅父项的 CheckedChanged 事件。

    ' When OwnerItem becomes available, if it is a ToolStripMenuItem 
' with a CheckOnClick property value of true, subscribe to its 
' CheckedChanged event. 
Protected Overrides Sub OnOwnerChanged(ByVal e As EventArgs)

    Dim ownerMenuItem As ToolStripMenuItem = _
        TryCast(OwnerItem, ToolStripMenuItem)

    If ownerMenuItem IsNot Nothing AndAlso _
        ownerMenuItem.CheckOnClick Then
        AddHandler ownerMenuItem.CheckedChanged, New _
            EventHandler(AddressOf OwnerMenuItem_CheckedChanged)
    End If

    MyBase.OnOwnerChanged(e)

End Sub

    // When OwnerItem becomes available, if it is a ToolStripMenuItem 
// with a CheckOnClick property value of true, subscribe to its 
// CheckedChanged event. 
protected override void OnOwnerChanged(EventArgs e)
{
    ToolStripMenuItem ownerMenuItem =
        OwnerItem as ToolStripMenuItem;
    if (ownerMenuItem != null && ownerMenuItem.CheckOnClick)
    {
        ownerMenuItem.CheckedChanged +=
            new EventHandler(OwnerMenuItem_CheckedChanged);
    }
    base.OnOwnerChanged(e);
}

  3. 在父项 CheckedChanged 事件的处理程序中，使项无效以通过新启用的状态更新显示。

    ' When the checked state of the parent item changes, 
' repaint the item so that the new Enabled state is displayed. 
Private Sub OwnerMenuItem_CheckedChanged( _
    ByVal sender As Object, ByVal e As EventArgs)
    Invalidate()
End Sub

    // When the checked state of the parent item changes, 
// repaint the item so that the new Enabled state is displayed. 
private void OwnerMenuItem_CheckedChanged(
    object sender, EventArgs e)
{
    Invalidate();
}

示例

下面的代码示例提供完整的 ToolStripRadioButtonMenuItem 类以及一个 Form 类和 Program 类以演示选项按钮行为。

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

Public Class ToolStripRadioButtonMenuItem
    Inherits ToolStripMenuItem

    Public Sub New()
        MyBase.New()
        Initialize()
    End Sub

    Public Sub New(ByVal text As String)
        MyBase.New(text, Nothing, CType(Nothing, EventHandler))
        Initialize()
    End Sub

    Public Sub New(ByVal image As Image)
        MyBase.New(Nothing, image, CType(Nothing, EventHandler))
        Initialize()
    End Sub

    Public Sub New(ByVal text As String, ByVal image As Image)
        MyBase.New(text, image, CType(Nothing, EventHandler))
        Initialize()
    End Sub

    Public Sub New(ByVal text As String, _
        ByVal image As Image, ByVal onClick As EventHandler)
        MyBase.New(text, image, onClick)
        Initialize()
    End Sub

    Public Sub New(ByVal text As String, ByVal image As Image, _
        ByVal onClick As EventHandler, ByVal name As String)
        MyBase.New(text, image, onClick, name)
        Initialize()
    End Sub

    Public Sub New(ByVal text As String, ByVal image As Image, _
        ByVal ParamArray dropDownItems() As ToolStripItem)
        MyBase.New(text, image, dropDownItems)
        Initialize()
    End Sub

    Public Sub New(ByVal text As String, ByVal image As Image, _
        ByVal onClick As EventHandler, ByVal shortcutKeys As Keys)
        MyBase.New(text, image, onClick)
        Initialize()
        Me.ShortcutKeys = shortcutKeys
    End Sub

    ' Called by all constructors to initialize CheckOnClick.
    Private Sub Initialize()
        CheckOnClick = True
    End Sub

    Protected Overrides Sub OnCheckedChanged(ByVal e As EventArgs)

        MyBase.OnCheckedChanged(e)

        ' If this item is no longer in the checked state or if its 
        ' parent has not yet been initialized, do nothing.
        If Not Checked OrElse Me.Parent Is Nothing Then Return

        ' Clear the checked state for all siblings. 
        For Each item As ToolStripItem In Parent.Items

            Dim radioItem As ToolStripRadioButtonMenuItem = _
                TryCast(item, ToolStripRadioButtonMenuItem)
            If radioItem IsNot Nothing AndAlso _
                radioItem IsNot Me AndAlso _
                radioItem.Checked Then

                radioItem.Checked = False

                ' Only one item can be selected at a time, 
                ' so there is no need to continue.
                Return

            End If
        Next

    End Sub

    Protected Overrides Sub OnClick(ByVal e As EventArgs)

        ' If the item is already in the checked state, do not call 
        ' the base method, which would toggle the value. 
        If Checked Then Return

        MyBase.OnClick(e)
    End Sub

    ' Let the item paint itself, and then paint the RadioButton
    ' where the check mark is normally displayed.
    Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)

        If Image IsNot Nothing Then
            ' If the client sets the Image property, the selection behavior
            ' remains unchanged, but the RadioButton is not displayed and the
            ' selection is indicated only by the selection rectangle. 
            MyBase.OnPaint(e)
            Return
        Else
            ' If the Image property is not set, call the base OnPaint method 
            ' with the CheckState property temporarily cleared to prevent
            ' the check mark from being painted.
            Dim currentState As CheckState = Me.CheckState
            Me.CheckState = CheckState.Unchecked
            MyBase.OnPaint(e)
            Me.CheckState = currentState
        End If

        ' Determine the correct state of the RadioButton.
        Dim buttonState As RadioButtonState = RadioButtonState.UncheckedNormal
        If Enabled Then
            If mouseDownState Then
                If Checked Then
                    buttonState = RadioButtonState.CheckedPressed
                Else
                    buttonState = RadioButtonState.UncheckedPressed
                End If
            ElseIf mouseHoverState Then
                If Checked Then
                    buttonState = RadioButtonState.CheckedHot
                Else
                    buttonState = RadioButtonState.UncheckedHot
                End If
            Else
                If Checked Then buttonState = RadioButtonState.CheckedNormal
            End If
        Else
            If Checked Then
                buttonState = RadioButtonState.CheckedDisabled
            Else
                buttonState = RadioButtonState.UncheckedDisabled
            End If
        End If

        ' Calculate the position at which to display the RadioButton.
        Dim offset As Int32 = CInt((ContentRectangle.Height - _
            RadioButtonRenderer.GetGlyphSize( _
            e.Graphics, buttonState).Height) / 2)
        Dim imageLocation As Point = New Point( _
            ContentRectangle.Location.X + 4, _
            ContentRectangle.Location.Y + offset)

        ' Paint the RadioButton. 
        RadioButtonRenderer.DrawRadioButton( _
            e.Graphics, imageLocation, buttonState)

    End Sub

    Private mouseHoverState As Boolean = False

    Protected Overrides Sub OnMouseEnter(ByVal e As EventArgs)
        mouseHoverState = True

        ' Force the item to repaint with the new RadioButton state.
        Invalidate()

        MyBase.OnMouseEnter(e)
    End Sub

    Protected Overrides Sub OnMouseLeave(ByVal e As EventArgs)
        mouseHoverState = False
        MyBase.OnMouseLeave(e)
    End Sub

    Private mouseDownState As Boolean = False

    Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
        mouseDownState = True

        ' Force the item to repaint with the new RadioButton state.
        Invalidate()

        MyBase.OnMouseDown(e)
    End Sub

    Protected Overrides Sub OnMouseUp(ByVal e As MouseEventArgs)
        mouseDownState = False
        MyBase.OnMouseUp(e)
    End Sub

    ' Enable the item only if its parent item is in the checked state 
    ' and its Enabled property has not been explicitly set to false. 
    Public Overrides Property Enabled() As Boolean
        Get
            Dim ownerMenuItem As ToolStripMenuItem = _
                TryCast(OwnerItem, ToolStripMenuItem)

            ' Use the base value in design mode to prevent the designer
            ' from setting the base value to the calculated value.
            If Not DesignMode AndAlso ownerMenuItem IsNot Nothing AndAlso _
                ownerMenuItem.CheckOnClick Then
                Return MyBase.Enabled AndAlso ownerMenuItem.Checked
            Else
                Return MyBase.Enabled
            End If
        End Get

        Set(ByVal value As Boolean)
            MyBase.Enabled = value
        End Set
    End Property

    ' When OwnerItem becomes available, if it is a ToolStripMenuItem 
    ' with a CheckOnClick property value of true, subscribe to its 
    ' CheckedChanged event. 
    Protected Overrides Sub OnOwnerChanged(ByVal e As EventArgs)

        Dim ownerMenuItem As ToolStripMenuItem = _
            TryCast(OwnerItem, ToolStripMenuItem)

        If ownerMenuItem IsNot Nothing AndAlso _
            ownerMenuItem.CheckOnClick Then
            AddHandler ownerMenuItem.CheckedChanged, New _
                EventHandler(AddressOf OwnerMenuItem_CheckedChanged)
        End If

        MyBase.OnOwnerChanged(e)

    End Sub

    ' When the checked state of the parent item changes, 
    ' repaint the item so that the new Enabled state is displayed. 
    Private Sub OwnerMenuItem_CheckedChanged( _
        ByVal sender As Object, ByVal e As EventArgs)
        Invalidate()
    End Sub

End Class

Public Class Form1
    Inherits Form

    Private menuStrip1 As New MenuStrip()
    Private mainToolStripMenuItem As New ToolStripMenuItem()
    Private toolStripMenuItem1 As New ToolStripMenuItem()
    Private toolStripRadioButtonMenuItem1 As New ToolStripRadioButtonMenuItem()
    Private toolStripRadioButtonMenuItem2 As New ToolStripRadioButtonMenuItem()
    Private toolStripRadioButtonMenuItem3 As New ToolStripRadioButtonMenuItem()
    Private toolStripRadioButtonMenuItem4 As New ToolStripRadioButtonMenuItem()
    Private toolStripRadioButtonMenuItem5 As New ToolStripRadioButtonMenuItem()
    Private toolStripRadioButtonMenuItem6 As New ToolStripRadioButtonMenuItem()

    Public Sub New()

        Me.mainToolStripMenuItem.Text = "main"
        toolStripRadioButtonMenuItem1.Text = "option 1"
        toolStripRadioButtonMenuItem2.Text = "option 2"
        toolStripRadioButtonMenuItem3.Text = "option 2-1"
        toolStripRadioButtonMenuItem4.Text = "option 2-2"
        toolStripRadioButtonMenuItem5.Text = "option 3-1"
        toolStripRadioButtonMenuItem6.Text = "option 3-2"
        toolStripMenuItem1.Text = "toggle"
        toolStripMenuItem1.CheckOnClick = True

        mainToolStripMenuItem.DropDownItems.AddRange(New ToolStripItem() { _
            toolStripRadioButtonMenuItem1, toolStripRadioButtonMenuItem2, _
            toolStripMenuItem1})
        toolStripRadioButtonMenuItem2.DropDownItems.AddRange( _
            New ToolStripItem() {toolStripRadioButtonMenuItem3, _
            toolStripRadioButtonMenuItem4})
        toolStripMenuItem1.DropDownItems.AddRange(New ToolStripItem() { _
            toolStripRadioButtonMenuItem5, toolStripRadioButtonMenuItem6})

        menuStrip1.Items.AddRange(New ToolStripItem() {mainToolStripMenuItem})
        Controls.Add(menuStrip1)
        MainMenuStrip = menuStrip1
        Text = "ToolStripRadioButtonMenuItem demo"
    End Sub
End Class

Public Class Program

    <STAThread()> Public Shared Sub Main()
        Application.EnableVisualStyles()
        Application.SetCompatibleTextRenderingDefault(False)
        Application.Run(New Form1())
    End Sub

End Class

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Windows.Forms.VisualStyles;

public class ToolStripRadioButtonMenuItem : ToolStripMenuItem
{
    public ToolStripRadioButtonMenuItem()
        : base()
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text)
        : base(text, null, (EventHandler)null)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(Image image)
        : base(null, image, (EventHandler)null)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text, Image image)
        : base(text, image, (EventHandler)null)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text, Image image,
        EventHandler onClick)
        : base(text, image, onClick)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text, Image image,
        EventHandler onClick, string name)
        : base(text, image, onClick, name)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text, Image image,
        params ToolStripItem[] dropDownItems)
        : base(text, image, dropDownItems)
    {
        Initialize();
    }

    public ToolStripRadioButtonMenuItem(string text, Image image,
        EventHandler onClick, Keys shortcutKeys)
        : base(text, image, onClick)
    {
        Initialize();
        this.ShortcutKeys = shortcutKeys;
    }

    // Called by all constructors to initialize CheckOnClick.
    private void Initialize()
    {
        CheckOnClick = true;
    }

    protected override void OnCheckedChanged(EventArgs e)
    {
        base.OnCheckedChanged(e);

        // If this item is no longer in the checked state or if its 
        // parent has not yet been initialized, do nothing.
        if (!Checked || this.Parent == null) return;

        // Clear the checked state for all siblings. 
        foreach (ToolStripItem item in Parent.Items)
        {
            ToolStripRadioButtonMenuItem radioItem =
                item as ToolStripRadioButtonMenuItem;
            if (radioItem != null && radioItem != this && radioItem.Checked)
            {
                radioItem.Checked = false;

                // Only one item can be selected at a time, 
                // so there is no need to continue.
                return;
            }
        }
    }

    protected override void OnClick(EventArgs e)
    {
        // If the item is already in the checked state, do not call 
        // the base method, which would toggle the value. 
        if (Checked) return;

        base.OnClick(e);
    }

    // Let the item paint itself, and then paint the RadioButton
    // where the check mark is normally displayed.
    protected override void OnPaint(PaintEventArgs e)
    {
        if (Image != null)
        {
            // If the client sets the Image property, the selection behavior
            // remains unchanged, but the RadioButton is not displayed and the
            // selection is indicated only by the selection rectangle. 
            base.OnPaint(e);
            return;
        }
        else
        {
            // If the Image property is not set, call the base OnPaint method 
            // with the CheckState property temporarily cleared to prevent
            // the check mark from being painted.
            CheckState currentState = this.CheckState;
            this.CheckState = CheckState.Unchecked;
            base.OnPaint(e);
            this.CheckState = currentState;
        }

        // Determine the correct state of the RadioButton.
        RadioButtonState buttonState = RadioButtonState.UncheckedNormal;
        if (Enabled)
        {
            if (mouseDownState)
            {
                if (Checked) buttonState = RadioButtonState.CheckedPressed;
                else buttonState = RadioButtonState.UncheckedPressed;
            }
            else if (mouseHoverState)
            {
                if (Checked) buttonState = RadioButtonState.CheckedHot;
                else buttonState = RadioButtonState.UncheckedHot;
            }
            else
            {
                if (Checked) buttonState = RadioButtonState.CheckedNormal;
            }
        }
        else
        {
            if (Checked) buttonState = RadioButtonState.CheckedDisabled;
            else buttonState = RadioButtonState.UncheckedDisabled;
        }

        // Calculate the position at which to display the RadioButton.
        Int32 offset = (ContentRectangle.Height -
            RadioButtonRenderer.GetGlyphSize(
            e.Graphics, buttonState).Height) / 2;
        Point imageLocation = new Point(
            ContentRectangle.Location.X + 4,
            ContentRectangle.Location.Y + offset);

        // Paint the RadioButton. 
        RadioButtonRenderer.DrawRadioButton(
            e.Graphics, imageLocation, buttonState);
    }

    private bool mouseHoverState = false;

    protected override void OnMouseEnter(EventArgs e)
    {
        mouseHoverState = true;

        // Force the item to repaint with the new RadioButton state.
        Invalidate();

        base.OnMouseEnter(e);
    }

    protected override void OnMouseLeave(EventArgs e)
    {
        mouseHoverState = false;
        base.OnMouseLeave(e);
    }

    private bool mouseDownState = false;

    protected override void OnMouseDown(MouseEventArgs e)
    {
        mouseDownState = true;

        // Force the item to repaint with the new RadioButton state.
        Invalidate();

        base.OnMouseDown(e);
    }

    protected override void OnMouseUp(MouseEventArgs e)
    {
        mouseDownState = false;
        base.OnMouseUp(e);
    }

    // Enable the item only if its parent item is in the checked state 
    // and its Enabled property has not been explicitly set to false. 
    public override bool Enabled
    {
        get
        {
            ToolStripMenuItem ownerMenuItem =
                OwnerItem as ToolStripMenuItem;

            // Use the base value in design mode to prevent the designer
            // from setting the base value to the calculated value.
            if (!DesignMode &&
                ownerMenuItem != null && ownerMenuItem.CheckOnClick)
            {
                return base.Enabled && ownerMenuItem.Checked;
            }
            else return base.Enabled;
        }
        set
        {
            base.Enabled = value;
        }
    }

    // When OwnerItem becomes available, if it is a ToolStripMenuItem 
    // with a CheckOnClick property value of true, subscribe to its 
    // CheckedChanged event. 
    protected override void OnOwnerChanged(EventArgs e)
    {
        ToolStripMenuItem ownerMenuItem =
            OwnerItem as ToolStripMenuItem;
        if (ownerMenuItem != null && ownerMenuItem.CheckOnClick)
        {
            ownerMenuItem.CheckedChanged +=
                new EventHandler(OwnerMenuItem_CheckedChanged);
        }
        base.OnOwnerChanged(e);
    }

    // When the checked state of the parent item changes, 
    // repaint the item so that the new Enabled state is displayed. 
    private void OwnerMenuItem_CheckedChanged(
        object sender, EventArgs e)
    {
        Invalidate();
    }

}

public class Form1 : Form
{
    private MenuStrip menuStrip1 = new MenuStrip();
    private ToolStripMenuItem mainToolStripMenuItem = new ToolStripMenuItem();
    private ToolStripMenuItem toolStripMenuItem1 = new ToolStripMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem1 = 
        new ToolStripRadioButtonMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem2 = 
        new ToolStripRadioButtonMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem3 = 
        new ToolStripRadioButtonMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem4 = 
        new ToolStripRadioButtonMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem5 = 
        new ToolStripRadioButtonMenuItem();
    private ToolStripRadioButtonMenuItem toolStripRadioButtonMenuItem6 = 
        new ToolStripRadioButtonMenuItem();

    public Form1()
    {
        mainToolStripMenuItem.Text = "main";
        toolStripRadioButtonMenuItem1.Text = "option 1";
        toolStripRadioButtonMenuItem2.Text = "option 2";
        toolStripRadioButtonMenuItem3.Text = "option 2-1";
        toolStripRadioButtonMenuItem4.Text = "option 2-2";
        toolStripRadioButtonMenuItem5.Text = "option 3-1";
        toolStripRadioButtonMenuItem6.Text = "option 3-2";
        toolStripMenuItem1.Text = "toggle";
        toolStripMenuItem1.CheckOnClick = true;

        mainToolStripMenuItem.DropDownItems.AddRange(new ToolStripItem[] {
            toolStripRadioButtonMenuItem1, toolStripRadioButtonMenuItem2,
            toolStripMenuItem1});
        toolStripRadioButtonMenuItem2.DropDownItems.AddRange(
            new ToolStripItem[] {toolStripRadioButtonMenuItem3, 
            toolStripRadioButtonMenuItem4});
        toolStripMenuItem1.DropDownItems.AddRange(new ToolStripItem[] {
            toolStripRadioButtonMenuItem5, toolStripRadioButtonMenuItem6});

        menuStrip1.Items.AddRange(new ToolStripItem[] {mainToolStripMenuItem});
        Controls.Add(menuStrip1);
        MainMenuStrip = menuStrip1;
        Text = "ToolStripRadioButtonMenuItem demo";
    }
}

static class Program
{
    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new Form1());
    }
}

编译代码

此示例要求：

  • 对 System、System.Drawing 和 System.Windows.Forms 程序集的引用。

请参见

任务

如何：实现自定义 ToolStripRenderer

参考

MenuStrip

ToolStripMenuItem

ToolStripMenuItem.CheckOnClick

ToolStripMenuItem.Checked

ToolStripMenuItem.OnCheckedChanged

ToolStripMenuItem.OnPaint

ToolStripMenuItem.Enabled

RadioButtonRenderer

其他资源

MenuStrip 控件（Windows 窗体）