C#

private void button2_Click(object sender, EventArgs e)
{
  for(int i = 0; i < checkedListBox1.CheckedItems.Count; i++)
  {
   if (!listBox1.Items.Contains(checkedListBox1.CheckedItems[i]))
   {
                    listBox1.Items.Add(checkedListBox1.CheckedItems[i]);

                    newPanel.Name = "panel " + (i+2).ToString();
                    newPanel.Location = new Point(405, 10);
                    newPanel.Parent = this;
                    newPanel.Size = new Size(341, 333);
                    newPanel.Visible = false;
                    newPanel.Controls.Add(nameLabel);
                    newPanel.Controls.Add(testButton);
                    listPanel.Add(newPanel);
                    newPanel.Show();
      }
   }
}

private void listBox1_MouseDoubleClick(object sender, MouseEventArgs e)
        {
            int index = this.listBox1.IndexFromPoint(e.Location);

            if(index != System.Windows.Forms.ListBox.NoMatches)
            {
                if(index < listPanel.Count - 1)
                {
                    //nameLabel.Text = "panel " + listPanel[index++].ToString();
                    listPanel[index++].Visible = true;
                    MessageBox.Show("" + listPanel.Count.ToString());
                    listPanel[--index].Show();

                }
            }
        }

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.IO;

namespace --------
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Label1_Click(object sender, EventArgs e)
        {

        }

        private void BtnLogin_Click(object sender, EventArgs e)
        {
            string Username = txtUsername.Text;
            string Password = txtPassword.Text;
            bool Found = false;

            string FilePath = "Login.csv";
            StreamReader fileReader = new StreamReader(FilePath);
            String[] details = File.ReadAllLines(FilePath);

            String[] splitted;
            foreach (string line in details)
            {
                splitted = line.Split(',');
                if (details[0] == Username && details[1] == Password)
                {
                    Found = true;
                }
            }
            if (Found == true)
            {
                Form2 Form2 = new Form2();
                Form2.Show();
                this.Hide();
            }
            else
            {
                AutoClosingMessageBox.Show("Incorrect Login Details Entered", "Error:", 5000);
            }
        }
    }
}
public class AutoClosingMessageBox
{
    System.Threading.Timer _timeoutTimer;
    string _caption;
    AutoClosingMessageBox(string text, string caption, int timeout)
    {
        _caption = caption;
        _timeoutTimer = new System.Threading.Timer(OnTimerElapsed,
            null, timeout, System.Threading.Timeout.Infinite);
        using (_timeoutTimer)
            MessageBox.Show(text, caption);
    }
    public static void Show(string text, string caption, int timeout)
    {
        new AutoClosingMessageBox(text, caption, timeout);
    }
    void OnTimerElapsed(object state)
    {
        IntPtr mbWnd = FindWindow("#32770", _caption);
        if (mbWnd != IntPtr.Zero)
            SendMessage(mbWnd, WM_CLOSE, IntPtr.Zero, IntPtr.Zero);
        _timeoutTimer.Dispose();
    }
    const int WM_CLOSE = 0x0010;
    [System.Runtime.InteropServices.DllImport("user32.dll", SetLastError = true)]
    static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
    [System.Runtime.InteropServices.DllImport("user32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto)]
    static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);
}