程序代码：

using System;
using System.Collections.Generic;
using using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
           

            this.TopLevel = false;
            this.FormBorderStyle = FormBorderStyle.None;
            this.BackColor = Color.Yellow;
            this.Size = new Size(150, 135);
            this.Location = new Point(50, 40);
        }
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using System;
using System.Collections.Generic;
using using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        private Form2 frm2;

        public Form1()
        {
            InitializeComponent();

            frm2 = new Form2();
            frm2.Visible = true;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.Controls.Add(frm2);
        }
    }
}