两个dropdownlist联动后，如何获取选中的项

以下是绑定的代码，如何才能获取选中后的值，请大家指点我一下，谢谢，我是新手


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;
using System.Data.SqlClient;

namespace WebApplication5
{
public partial class add : System.Web.UI.Page
{

string strCon = "Data Source=(local);Database=LOGINDB;Uid=sa;Pwd=sa123456";


protected void Page_Load(object sender, EventArgs e)
{

if (!IsPostBack)
{
//绑定ddlxueli
SqlConnection con = new SqlConnection(strCon);
con.Open();
SqlCommand cmd = new SqlCommand("select * from class ", con);
SqlDataReader reader = cmd.ExecuteReader();
ddlxueli.DataSource = reader;
ddlxueli.DataTextField = "classname";
ddlxueli.DataValueField = "classno";
ddlxueli.DataBind();
reader.Close();

//绑—ropDownList1
SqlCommand cmd2 = new SqlCommand("select * from deviceinfo where classno=" + this.ddlxueli.SelectedValue, con);
reader = cmd2.ExecuteReader();//上面定义过reader，这里就不用从新定义
DropDownList1.DataSource = reader;
DropDownList1.DataTextField = "deviceno";
DropDownList1.DataValueField = "classno";
DropDownList1.DataBind();
reader.Close();



}


}

protected void btnRegion_Click(object sender, EventArgs e)
{

}



protected void ddlxueli_SelectedIndexChanged(object sender, EventArgs e)
{
//DropDownList1与DropDownList2数据绑定的联动性
string code = this.ddlxueli.SelectedValue;
SqlConnection con = new SqlConnection(strCon);
con.Open();
SqlCommand cmd = new SqlCommand("select * from deviceinfo where classno=" + code, con);
SqlDataReader reader = cmd.ExecuteReader();
this.DropDownList1.DataSource = reader;
this.DropDownList1.DataTextField = "deviceno";
this.DropDownList1.DataValueField = "classno";
this.DropDownList1.DataBind();
reader.Close();
con.Close();

}

protected void txt_TextChanged(object sender, EventArgs e)
{

}


}
}


[解决办法]
SelectedIndex
[解决办法]
DropDownList1.SelectedIndex就可以获取到你选定的是哪个啊
[解决办法]
SelectedValue