How to insert multiple rows in datagrid without db connection?

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C#

Hi, I tried to insert data into datagrid view. But the think is when i tried to insert second row, it replace the existing row in datagrid cell. Can anyone help me to display multiple rows in datagrid view cell without database connection?

What I have tried:

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;
using System.Web;

namespace task2
{
    public partial class Form1 : Form
    {
        private DataTable myTable = new DataTable();

        public Form1()
        {
            InitializeComponent();
            this.initialiseTable(this.myTable);
            this.dataGridView1.DataSource = this.myTable;
        }
        private void CLEAR_Click(object sender, EventArgs e)
        {
            Name.Text = "";
            LastName.Text = "";
            lsGender.Text = "";
            phone.Text = "";
            mail.Text = "";
        }
        private void CLOSE_Click(object sender, EventArgs e)
        {
            this.Close();
        }
        private void initialiseTable(DataTable table)
        {
            table.Columns.Add(new DataColumn("Column1"));
            table.Columns.Add(new DataColumn("Column2"));
            table.Columns.Add(new DataColumn("Column3"));
        }


        private void ADD_Click(object sender, EventArgs e)
        {
            
           
            DataRow rd = this.myTable.NewRow();
            rd[0] = Name.Text;
            rd[1] = LastName.Text;
            rd[2] = lsGender.SelectedItem;
            this.myTable.Rows.Add(rd);
        }          
    }
}