Add multiple values from listbox1 to listbox2

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="WebApplication9._Default" %>





   


   

   

                  SelectionMode="Multiple">
   
  
                SelectionMode="Multiple">
           
   

   
   

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

namespace WebApplication9
{
    public partial class _Default : System.Web.UI.Page
    {
        ArrayList arraylist1 = new ArrayList();
        ArrayList arraylist2 = new ArrayList();

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                ListBox1.Items.Add("Raj");
                ListBox1.Items.Add("Ravi");
                ListBox1.Items.Add("Rahul");
                ListBox1.Items.Add("Raju");
                ListBox1.Items.Add("Rohit");
                ListBox1.Items.Add("Rajesh");
            }
        }

        protected void Button1_Click(object sender, EventArgs e)
        {

            lbltxt.Visible = false;
            if (ListBox2.SelectedIndex >= 0)
            {
                for (int i = 0; i < ListBox2.Items.Count; i++)
                {
                    if (ListBox2.Items[i].Selected)
                    {
                        if (!arraylist2.Contains(ListBox2.Items[i]))
                        {
                            arraylist2.Add(ListBox2.Items[i]);
                        }
                    }
                }
                for (int i = 0; i < arraylist2.Count; i++)
                {
                    if (!ListBox1.Items.Contains(((ListItem)arraylist2[i])))
                    {
                        ListBox1.Items.Add(((ListItem)arraylist2[i]));
                    }
                    ListBox2.Items.Remove(((ListItem)arraylist2[i]));
                }
                ListBox1.SelectedIndex = -1;
            }
            else
            {
                lbltxt.Visible = true;
                lbltxt.Text = "Please select atleast one in Listbox2 to move";
            }

           
        }

        protected void Button2_Click(object sender, EventArgs e)
        {
     

                lbltxt.Visible = false;
            if (ListBox1.SelectedIndex >= 0)
            {
                for (int i = 0; i < ListBox1.Items.Count; i++)
                {
                    if (ListBox1.Items[i].Selected)
                    {
                        if (!arraylist1.Contains(ListBox1.Items[i]))
                        {
                            arraylist1.Add(ListBox1.Items[i]);
                        }
                    }
                }
                for (int i = 0; i < arraylist1.Count; i++)
                {
                    if (!ListBox2.Items.Contains(((ListItem)arraylist1[i])))
                    {
                        ListBox2.Items.Add(((ListItem)arraylist1[i]));
                    }
                    ListBox1.Items.Remove(((ListItem)arraylist1[i]));
                }
                ListBox2.SelectedIndex = -1;
            }
            else
            {
                lbltxt.Visible = true;
                lbltxt.Text = "Please select atleast one in Listbox1 to move";
            }
        }
    }
}