修改此代码（private void TabPage_CloseButtonClick(object sender, EventArgs e) { Button closeButton = (Button)sender; TabPage tabPage = (TabPage)closeButton.Tag; Form form = (Form)tabPage.Tag; form.Close(); stabControl1.TabPages.Remove(tabPage); }）修改为tabpage标签标题中添加关闭按钮

以下是修改后的代码，它会在每个标签的标题中添加一个关闭按钮，并在单击该按钮时关闭相关的选项卡和窗体：

private void AddCloseButtonToTabPage(TabPage tabPage)
{
    // 创建一个关闭按钮
    Button closeButton = new Button();
    closeButton.Text = "×";
    closeButton.Size = new Size(16, 16);
    closeButton.FlatStyle = FlatStyle.Flat;
    closeButton.BackColor = Color.Transparent;
    closeButton.ForeColor = Color.Red;
    closeButton.FlatAppearance.BorderSize = 0;
    closeButton.TabStop = false;

    // 设置关闭按钮的位置和大小
    Rectangle rect = tabPage.GetTabRect(tabPage.Controls.Count - 1);
    closeButton.Location = new Point(rect.Right - closeButton.Width, rect.Top + (rect.Height - closeButton.Height) / 2);

    // 将关闭按钮添加到标签页中
    tabPage.Controls.Add(closeButton);

    // 为关闭按钮绑定事件
    closeButton.Click += (sender, e) =>
    {
        TabPage tabPage = (sender as Button).Parent as TabPage;
        Form form = tabPage.Tag as Form;
        form.Close();
        tabControl1.TabPages.Remove(tabPage);
    };
}

private void tabControl1_SelectedIndexChanged(object sender, EventArgs e)
{
    // 添加关闭按钮到当前选中的标签页
    TabPage tabPage = tabControl1.SelectedTab;
    AddCloseButtonToTabPage(tabPage);
}

private void tabControl1_ControlAdded(object sender, ControlEventArgs e)
{
    // 添加关闭按钮到新添加的标签页
    TabPage tabPage = e.Control as TabPage;
    AddCloseButtonToTabPage(tabPage);
}