Asp.net中ListBox的用法！

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Collections;

namespace Vocation
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                ArrayList a = new ArrayList();
                a.Add("asp.net");
                a.Add("JavaScript");
                a.Add("CSS");
                a.Add("Html");
                a.Add("C#");
                ListBox2.DataSource = a;
                ListBox2.DataBind();
            }

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            foreach (ListItem item in ListBox2.Items)
            {
                ListBox3.Items.Add(item);
               

            }
            ListBox2.Items.Clear();
        }

        protected void Button3_Click(object sender, EventArgs e)
        {

            foreach (ListItem item in ListBox3.Items)
            {
                ListBox2.Items.Add(item);
               

            }
            ListBox3.Items.Clear();
        }

        protected void Button2_Click(object sender, EventArgs e)
        {
           //左边------右边
            if (ListBox2.SelectedIndex != -1)
            {
                foreach (ListItem item in ListBox2.Items)
                {
                    if (item.Selected)
                    {
                        ListBox3.Items.Add(item);
                    }

                }
            }
            for (int index = ListBox2.Items.Count-1; index>=0; index--)
            {
                if (ListBox2.Items[index].Selected)
                {
                    ListBox2.Items.RemoveAt(index);
                }
            }

            
        }

        protected void Button4_Click(object sender, EventArgs e)
        {
            if (ListBox3.SelectedIndex != -1)
            {
                foreach (ListItem item in ListBox3.Items)
                {
                    if (item.Selected)
                    {
                        ListBox2.Items.Add(item);
                    }

                }
            }
            for (int index = ListBox3.Items.Count - 1; index >= 0; index--)
            {
                if (ListBox3.Items[index].Selected)
                {
                    ListBox3.Items.RemoveAt(index);
                }
            }
        }

        protected void Button5_Click(object sender, EventArgs e)
        {
            Label1.Text = "你选择的科目为：";
            foreach(ListItem item in ListBox3.Items)
            {
                Label1.Text+=item.Text +" ";
            }
            
        }
    }
}

值得注意的是在WEB控件中，listbox的selecteditem并不是指的当前选定的值，而是最小值，这点与winform不同。所以在上面没有用selecteditem来取值，而是遍历后用item.text