Winform 中实现省市联动效果

1，省的ID，Name直接定义成类，实例化后添加的到ComBox（DropDrownList）中，DisplayMember设置为ProName

2，绑定后SelectedIndex=0，显示绑定的第一个值

3，Configure中设置连接字符串，ConfigurationManager 中得到字符串的值

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;
using System.Configuration;

namespace 省市联动
{
    public partial class 省市联动 : Form
    {
        public 省市联动()
        {
            InitializeComponent();
        }

        private void 省市联动_Load(object sender, EventArgs e)
        {
            BindPro();
            //显示第一个 Province
            cmbBoxPro.SelectedIndex = 0;
        }
        //省发生变化的时候的事件
        private void cmbBoxPro_SelectedIndexChanged(object sender, EventArgs e)
        {
            ProIDSeled();
            //显示第一个 City
            cmbCity.SelectedIndex = 0;
        }

        //获取所选取的省的ID
        protected void ProIDSeled()
        {
            //
            ProCity ProSeled = new ProCity();
            ProSeled = (ProCity)cmbBoxPro.SelectedItem;  //选中项是 PorCity 的实例 

            if (ProSeled != null)
            {
                int numProIDSeled = ProSeled.ProID;
                string strProName = ProSeled.ProName;

                //绑定之前先把数据清除
                cmbCity.Items.Clear();
                cmbCity.SelectedItem = null;
                BindCity(numProIDSeled);   //市也相应变化
                //MessageBox.Show(numProIDSeled.ToString());
            }
        }


        //绑定省
        protected void BindPro()
        {
            string strConn = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;
            using (SqlConnection conn = new SqlConnection(strConn))
            {
                conn.Open();
                string strSelPro = "SELECT   proID, proName FROM  Province";
                using (SqlCommand sqlCmd = new SqlCommand(strSelPro, conn))
                {
                    using (SqlDataReader sdr = sqlCmd.ExecuteReader())
                    {
                        while (sdr.Read())
                        {
                            ProCity PCity = new ProCity();
                            int numProID = sdr.GetInt32(sdr.GetOrdinal("ProID"));
                            string strProName = sdr.GetValue(sdr.GetOrdinal("ProName")).ToString();
                            PCity.ProID = numProID;
                            PCity.ProName = strProName;
                            cmbBoxPro.Items.Add(PCity);   //控件添加的是类
                        }
                    }
                }
            }
        }

        //绑定市
        protected void BindCity(int proID)
        {
            string strConn = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;
            using (SqlConnection conn = new SqlConnection(strConn))
            {
                conn.Open();
                string strSelPro = "SELECT   cityID, cityName, proID FROM city where proID=@proId ";
                SqlParameter sqlParaCity = new SqlParameter("proId", proID);
                using (SqlCommand sqlCmd = new SqlCommand(strSelPro, conn))
                {
                    sqlCmd.Parameters.Add(sqlParaCity);
                    using (SqlDataReader sdr = sqlCmd.ExecuteReader())
                    {
                        while (sdr.Read())
                        {
                            int numCityID = sdr.GetInt32(sdr.GetOrdinal("cityID"));
                            string strCityName = sdr.GetValue(sdr.GetOrdinal("cityName")).ToString();
                            cmbCity.Items.Add(strCityName);   //控件添加的是类

                            //参数清除
                            sqlCmd.Parameters.Clear();
                        }
                    }
                }
            }
        }

        //定义一个省市的类
        public class ProCity
        {
            private int proID;
            private string proName;
            public int ProID
            {
                get
                {
                    return proID;
                }
                set
                {
                    this.proID = value;
                }
            }
            public string ProName
            {
                get
                {
                    return this.proName;
                }
                set
                {
                    this.proName = value;
                }
            }
        }
    }
}

配置文件中的字符串 App.Config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
    <add name="ConnStr" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\DBProvince.mdf;Integrated Security=True;User Instance=True"/>
  </connectionStrings>
</configuration>