How to create multiple selections in combobox using C# windows application

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.Windows.Forms.VisualStyles;

namespace MultiselectDropdownlist
{
    public partial class Form1 : Form
    {
        public bool chk = false;
        public Form1()
        {
            InitializeComponent();
            Loadnamesofcountry();
            displaypanel.Visible = false;
           
        }

        private void Loadnamesofcountry()
        {
            cmbCountrylist.Items.Add("India");
            cmbCountrylist.Items.Add("US");
            cmbCountrylist.Items.Add("UK");
            cmbCountrylist.Items.Add("Switzerland");
            cmbCountrylist.Items.Add("Brezil");
        }

        private void cmbCountrylist_SelectedIndexChanged(object sender, EventArgs e)
        {
         
            lblOutput.Text = cmbCountrylist.Text;
     
        }