winform TabControl添加删除键

在 WinForm TabControl 中添加删除键可以让用户更方便地关闭 TabPage，以下是实现步骤：

1. 在 TabControl 控件上添加一个 ContextMenuStrip 上下文菜单，菜单项为“关闭当前选项卡”。

2. 在 TabControl 的 MouseClick 事件中判断是否右键单击，如果是，则弹出上下文菜单。

3. 在上下文菜单的 Click 事件中关闭当前选项卡。

4. （可选）在 TabControl 控件上添加一个 Button 控件，点击该按钮时关闭当前选项卡。

示例代码如下：

public partial class CustomTabControl : TabControl
{
    private ContextMenuStrip _contextMenuStrip;
    private Button _closeButton;

    public CustomTabControl()
    {
        InitializeComponent();
        InitContextMenu();
        InitCloseButton();
    }

    private void InitContextMenu()
    {
        _contextMenuStrip = new ContextMenuStrip();
        var closeMenuItem = new ToolStripMenuItem("关闭当前选项卡");
        closeMenuItem.Click += CloseMenuItem_Click;
        _contextMenuStrip.Items.Add(closeMenuItem);
    }

    private void InitCloseButton()
    {
        _closeButton = new Button
        {
            Width = 20,
            Height = 20,
            FlatStyle = FlatStyle.Flat,
            ForeColor = Color.Gray,
            Font = new Font("Marlett", 8.25f),
            Text = "r",
            Visible = false
        };
        _closeButton.Click += CloseButton_Click;
        Controls.Add(_closeButton);
    }

    protected override void OnControlAdded(ControlEventArgs e)
    {
        base.OnControlAdded(e);
        e.Control.MouseEnter += Control_MouseEnter;
        e.Control.MouseLeave += Control_MouseLeave;
        e.Control.MouseDown += Control_MouseDown;
    }

    protected override void OnControlRemoved(ControlEventArgs e)
    {
        base.OnControlRemoved(e);
        e.Control.MouseEnter -= Control_MouseEnter;
        e.Control.MouseLeave -= Control_MouseLeave;
        e.Control.MouseDown -= Control_MouseDown;
    }

    private void Control_MouseEnter(object sender, EventArgs e)
    {
        _closeButton.Visible = true;
        _closeButton.Top = 2;
        _closeButton.Left = GetCloseButtonLeft((TabPage)sender) - _closeButton.Width;
    }

    private void Control_MouseLeave(object sender, EventArgs e)
    {
        _closeButton.Visible = false;
    }

    private void Control_MouseDown(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
        {
            SelectedTab = (TabPage)sender;
        }
        else if (e.Button == MouseButtons.Right)
        {
            SelectedTab = (TabPage)sender;
            _contextMenuStrip.Show(this, e.Location);
        }
    }

    private void CloseMenuItem_Click(object sender, EventArgs e)
    {
        if (SelectedTab != null)
        {
            TabPages.Remove(SelectedTab);
        }
    }

    private void CloseButton_Click(object sender, EventArgs e)
    {
        var closeButton = (Button)sender;
        var tabPage = (TabPage)closeButton.Tag;
        TabPages.Remove(tabPage);
    }

    private int GetCloseButtonLeft(TabPage tabPage)
    {
        var closeButtonWidth = _closeButton.Width;
        var closeButtonPadding = 2;
        var tabRect = GetTabRect(TabPages.IndexOf(tabPage));
        return tabRect.Right - closeButtonPadding - closeButtonWidth;
    }

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

        foreach (TabPage tabPage in TabPages)
        {
            var closeButtonLeft = GetCloseButtonLeft(tabPage);
            tabPage.Controls[0].Left = closeButtonLeft;
        }
    }
}

在该自定义控件中，我们添加了一个 Button 控件作为关闭按钮，当用户鼠标移入 TabPage 区域时，该按钮才会显示。同时，我们还添加了一个上下文菜单，用户右键单击 TabPage 时，可以选择关闭当前选项卡。