C# MDI 简单实现

// TabPage
for (int i = 0; i < 4; i++)
{
    TabPage page = new TabPage();
    page.Text = i.ToString();
    tabControl1.Controls.Add(page);
    page.Controls.Add(new Form2 { TopLevel = false, Dock = DockStyle.Fill, BackColor = Color.Orange, FormBorderStyle = FormBorderStyle.None, Visible = true });
}

// Panel
Form2 f = new Form2() { TopLevel = false, Dock = DockStyle.Fill, BackColor = Color.Orange, FormBorderStyle = FormBorderStyle.None, Visible = true };
panel1.Controls.Add(f);