%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> 
 
!DOCTYPE html> 
 
html xmlns="http://www.w3.org/1999/xhtml"> 
head runat="server"> 
meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> 
 title>/title> 
/head> 
body> 
 form id="form1" runat="server"> 
 div> 
 
 asp:DropDownList ID="ddlDep" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlDep_SelectedIndexChanged"> 
 /asp:DropDownList> 
 br /> 
 asp:ListBox ID="lBoxEmp" runat="server">/asp:ListBox> 
 
 /div> 
 /form> 
/body> 
/html> 

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Data.SqlClient; 
 
public partial class _Default : System.Web.UI.Page 
{ 
 protected void Page_Load(object sender, EventArgs e) 
 { 
 if (!this.IsPostBack) 
 { 
 SqlConnection con = DBCon.createConnection(); 
 con.Open(); 
 //显示部门 
 SqlCommand cmd = new SqlCommand("select * from Tdepartment", con); 
 SqlDataReader sdr = cmd.ExecuteReader(); 
 this.ddlDep.DataSource = sdr; 
 this.ddlDep.DataTextField = "depName"; 
 this.ddlDep.DataValueField = "depID"; 
 this.ddlDep.DataBind(); 
 sdr.Close(); 
 //显示员工 
 SqlCommand cmdEmp =new SqlCommand ("select * from emp where depID=" + this.ddlDep .SelectedValue ,con); 
 SqlDataReader sdrEmp = cmdEmp.ExecuteReader(); 
 while (sdrEmp.Read()) 
 { 
 this.lBoxEmp.Items.Add (new ListItem(sdrEmp.GetString(1),sdrEmp .GetInt32 (0).ToString ())); 
 } 
 sdrEmp.Close(); 
 //关闭连接 
 con.Close(); 
 } 
 } 
 protected void ddlDep_SelectedIndexChanged(object sender, EventArgs e) 
 { 
 this.lBoxEmp.Items.Clear(); 
 SqlConnection con = DBCon.createConnection(); 
 con.Open(); 
 SqlCommand cmdEmp = new SqlCommand("select * from emp where depID=" + this.ddlDep.SelectedValue, con); 
 SqlDataReader sdrEmp = cmdEmp.ExecuteReader(); 
 while (sdrEmp.Read()) 
 { 
 this.lBoxEmp.Items.Add(new ListItem(sdrEmp.GetString(1), sdrEmp.GetInt32(0).ToString())); 
 } 
 sdrEmp.Close(); 
 //关闭连接 
 con.Close(); 
 } 
} 

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Data.SqlClient; 
 
/// summary> 
/// DBCon 的摘要说明 
/// /summary> 
public class DBCon 
{ 
 public DBCon() 
 { 
 // 
 // TODO: 在此处添加构造函数逻辑 
 // 
 } 
 public static SqlConnection createConnection() 
 { 
 SqlConnection con = new SqlConnection("server=.;database=department;uid=sa;pwd=123456"); 
 return con; 
 } 
}