在按钮单击事件中，您执行以下操作：

In the button click event, you do:

Form2 frm = new Form2();  //Or whatever your form is called
frm.Show(this);

或（如果你想以模态方式打开它）：

or (if you want to open it modally):

Form2 frm = new Form2();  //Or whatever your form is called
frm.ShowDialog(this);

您还需要在tabpages的控件集合中添加表单对象，如下所示：

You also need to add form object in tabpages'' control collection as below:

private void button1_Click(object sender, EventArgs e)
{
    Form2 frm = new Form2();
    frm.TopLevel = false;
    tabPage1.Controls.Add(frm);
    frm.Dock = DockStyle.Fill;
    frm.Show();
}

检查这个

选项卡式MDI子窗体 [ ^ ]