大家帮忙解决下，写两个asp算法代码

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

namespace WebApplication1
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            string SelVal = this.DropDownList1.SelectedItem.Text;
            switch (SelVal)
            {
                case "出勤":
                    Response.Write("这是出勤的代码");
                    break;
                case "旷课":
                    Response.Write("旷课的代码");
                    break;
                case "迟到":
                    Response.Write("迟到的代码");
                    break;
                case "早退":
                    Response.Write("早退的代码");
                    break;
                case "违纪":
                    Response.Write("违纪的代码");
                    break;
            }

        }
    }
}

        <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"
            onselectedindexchanged="DropDownList1_SelectedIndexChanged">
            <asp:ListItem Selected="True" Value="+5">出勤</asp:ListItem>
            <asp:ListItem Value="-3">旷课</asp:ListItem>
            <asp:ListItem Value="-3">迟到</asp:ListItem>
            <asp:ListItem Value="-3">早退</asp:ListItem>
            <asp:ListItem Value="-5">违纪</asp:ListItem>
        </asp:DropDownList>