Step 1: Click New Project, then select Visual C# on the left, then Windows and then select Windows Forms Application. Name your project "MdiForm" and then click OK
Step 2: Design your form as below

From the Toolbox, drag a MenuStrip control to the form, then add items to your menu
You need to create an empty Form2 to play demo, as same as Form3, Form4, Form5
Step 3: Add code to handle your form as below
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace MdiForm
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
//Show MDI form
private void ShowForm(Form frm)
{
frm.MdiParent = this;
frm.Show();
frm.Activate();
}
private void form1ToolStripMenuItem_Click(object sender, EventArgs e)
{
ShowForm(Form2.Instance);
}
private void form2ToolStripMenuItem_Click(object sender, EventArgs e)
{
ShowForm(Form3.Instance);
}
private void form3ToolStripMenuItem_Click(object sender, EventArgs e)
{
Form4 frm = new Form4();
frm.MdiParent = this;
frm.Show();
}
private void form4ToolStripMenuItem_Click(object sender, EventArgs e)
{
Form5 frm = new Form5();
frm.MdiParent = this;
frm.Show();
}
}
}
VIDEO TUTORIALS