webform1.aspx.cs

从数据库中读取并添加到下拉列表中

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;

namespace dropdown_listbox
{
	/// <summary>
	/// WebForm1 的摘要说明。
	/// </summary>
	public class WebForm1 : System.Web.UI.Page
	{
		protected System.Web.UI.WebControls.Label Label1;
		protected System.Web.UI.WebControls.Label Label2;
		protected System.Web.UI.WebControls.DropDownList DropDownList1;
		protected System.Web.UI.WebControls.Label Label3;
		protected System.Web.UI.WebControls.ListBox ListBox1;
	
		private void Page_Load(object sender, System.EventArgs e)
		{
			// 在此处放置用户代码以初始化页面
			if(!this.IsPostBack)
			{
				SqlConnection con=DB.createconnection();
				con.Open();

				SqlCommand cmd=new SqlCommand("select * from department",con);
				SqlDataReader sdr=cmd.ExecuteReader();

				this.DropDownList1.DataSource=sdr;
				this.DropDownList1.DataTextField="departmentName";
				this.DropDownList1.DataValueField="departmentID";
				this.DropDownList1.DataBind();

				sdr.Close();

				SqlCommand cmd_employ=new SqlCommand("select * from employ where departmentID="+this.DropDownList1.SelectedValue,con);
				SqlDataReader sdr_employ=cmd_employ.ExecuteReader();
//				this.ListBox1.DataSource=sdr_employ;
//				this.ListBox1.DataTextField="employName";
//				this.ListBox1.DataValueField="employID";
//				this.ListBox1.DataBind();
				while(sdr_employ.Read())
				{
					this.ListBox1.Items.Add(new ListItem(sdr_employ.GetString(1),sdr_employ.GetInt32(0).ToString()));
				}

				sdr.Close();
				con.Close();
			}
		}

		#region Web 窗体设计器生成的代码
		override protected void OnInit(EventArgs e)
		{
			//
			// CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
			//
			InitializeComponent();
			base.OnInit(e);
		}
		
		/// <summary>
		/// 设计器支持所需的方法 - 不要使用代码编辑器修改
		/// 此方法的内容。
		/// </summary>
		private void InitializeComponent()
		{    
			this.DropDownList1.SelectedIndexChanged += new System.EventHandler(this.DropDownList1_SelectedIndexChanged);
			this.Load += new System.EventHandler(this.Page_Load);

		}
		#endregion

		private void DropDownList1_SelectedIndexChanged(object sender, System.EventArgs e)
		{
			this.ListBox1.Items.Clear();
			SqlConnection con=DB.createconnection();
			con.Open();

			SqlCommand cmd1=new SqlCommand("select * from employ where departmentID="+this.DropDownList1.SelectedValue,con);
			SqlDataReader sdr1=cmd1.ExecuteReader();

			while(sdr1.Read())
			{
				this.ListBox1.Items.Add(new ListItem(sdr1.GetString(1),sdr1.GetInt32(0).ToString()));
			}

//
//			this.ListBox1.DataSource=sdr;
//			this.ListBox1.DataTextField="employName";
//			this.ListBox1.DataValueField="employID";
//			this.ListBox1.DataBind();

			sdr1.Close();
			con.Close();
		}
	}
}