C# winform 選擇項 省市連動

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using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;using System.Data.SqlClient;namespace 省市聯動{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();        }        private void Form1_Load(object sender, EventArgs e)        {            //載入省份資訊到第一個ComboBox            LoadProvince();            //設定兩個下拉式功能表的預設值為“請選擇”            comboBox1.SelectedIndex = 0;            comboBox2.SelectedIndex = 0;        }        private void LoadProvince()        {            string sql = "select * from TblArea where AreaPid=0";            using (SqlDataReader reader = SqlHelper.ExecuteReader(sql))            {                if (reader.HasRows)                {                    while (reader.Read())                    {                        ProvinceItem item = new ProvinceItem();                        item.AreaId = reader.GetInt32(0);                        item.AreaName = reader.GetString(1);                        item.AreaPid = reader.GetInt32(2);                        comboBox1.Items.Add(item);                    }                }            }            //為ComboBox 增加一個“請選擇”            ProvinceItem itemDefault = new ProvinceItem();            itemDefault.AreaId = -1;            itemDefault.AreaName = "請選擇";            comboBox1.Items.Insert(0, itemDefault);        }        //下拉式功能表的選擇項改變事件        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)        {            //擷取目前使用者選擇的項            if (comboBox1.SelectedIndex > 0)            {                //載入第二個下拉式功能表，資料來源：根據第一個下拉式功能表使用者選擇項的AreaId來查詢該項的所有子項。(子項：指的就是當前選中省份的下的直接城市)                //擷取當前選中項的id                ProvinceItem item = comboBox1.SelectedItem as ProvinceItem;                int areaId = item.AreaId;                LoadCity(areaId);            }        }        private void LoadCity(int areaId)        {            comboBox2.Items.Clear();            string sql = "select * from TblArea where [email protected]";            using (SqlDataReader reader = SqlHelper.ExecuteReader(sql, new SqlParameter("@aid", areaId)))            {                if (reader.HasRows)                {                    while (reader.Read())                    {                        ProvinceItem item = new ProvinceItem();                        item.AreaId = reader.GetInt32(0);                        item.AreaName = reader.GetString(1);                        item.AreaPid = reader.GetInt32(2);                        comboBox2.Items.Add(item);                    }                }            }            //也加一個【請選擇】            ProvinceItem itemDefault = new ProvinceItem();            itemDefault.AreaId = -1;            itemDefault.AreaName = "請選擇";            comboBox2.Items.Insert(0, itemDefault);            comboBox2.SelectedIndex = 0;        }    }    public class ProvinceItem    {        public int AreaId { get; set; }        public string AreaName { get; set; }        public int AreaPid { get; set; }        public override string ToString()        {            return this.AreaName;        }    }}

 

C# winform 選擇項 省市連動