省与市的联动 WinF窗体用ComboBox控件实现省与市的联动效果。

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 Form1 : Form    {        public Form1()        {            InitializeComponent();        }        private void Form1_Load(object sender, EventArgs e)        {            Tsql.GetConnection();            using (SqlConnection conn = new SqlConnection(Tsql.GetConnection()))            {                conn.Open();                using (SqlCommand cmd = conn.CreateCommand())                {                    cmd.CommandText = "select * from promary";                    using (SqlDataReader dr = cmd.ExecuteReader())                    {                        while (dr.Read())                        {                            Province pr = new Province();                            pr.proID = dr.GetInt32(dr.GetOrdinal("proID"));  //这里要特别注意数据库字段的类型 proID在数据库里是int型                            pr.proName = dr.GetString(dr.GetOrdinal("proName"));                            comboBox1.Items.Add(pr);//pr是一个Province对象。Province有一个proName和proID属性。我将一个对象填充到comboBox1里。再让comboBox1的DisplayMember属性设置proName。【也就是让comboBox1显示pr对象的proName属性】。这样在填充市级城市的时候我就可以找到当前选择项comboBox1.SelectedItem（或者当前选择对象）所对应的proID                                                    }                    }                                   }                comboBox1.SelectedIndex = 0;  //将comcomboBox1的默认选项设为0            }                    }        private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)        {        }        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)        {            comboBox2.Items.Clear(); //在选择的时候先清空一下combox1里面的所以项，以免在更换省名的时候，与先前对应的省名下的市没有删除。            Province tem = (Province)comboBox1.SelectedItem; // 因为在comboBox1.Items.Add(pr)里添加的是对象。所以在这里讲comBox1所选中的当前对象赋给tem对象 （tem对象下面有两个属性 proName和proID）                        int id = tem.proID;  //将当前选中对象的的proID赋值给id，给下面的sql查询语句使用            Tsql.GetConnection();// 获取数据库连接字符串。            using (SqlConnection conn = new SqlConnection(Tsql.GetConnection()))            {                conn.Open();                using (SqlCommand cmd = conn.CreateCommand())                {                                        cmd.CommandText = "select * from city where proID=@id";                    cmd.Parameters.Add(new SqlParameter("id", id));                    using (SqlDataReader dr = cmd.ExecuteReader())                    {                        while (dr.Read())                        {                            comboBox2.Items.Add(dr.GetString(dr.GetOrdinal("cityName")));                        }                    }                }                comboBox2.SelectedIndex = 0; //将comcomboBox1的默认选项设为0            }        }    }    class Tsql    {        public static string GetConnection() //数据库连接字符串        {            string getConn = ConfigurationManager.ConnectionStrings["getConn"].ConnectionString;            return getConn;        }           }    class Province    {        public string proName { get; set; }        public int proID { get; set; }    }}

using System.Data.SqlClient;

 

namespace 省市选择2

{

    public partial class Form1 : Form

    {

        publicForm1()

        {

            InitializeComponent();

        }

 

        privatevoid Form1_Load(objectsender,EventArgs e)

        {

            /*

            //测试代码：执行这段代码的情况下是可以吧 tom这个值添加到 comboBox1中的。

            People p1 = new People();

            p1.name = "tom";

            p1.age = 25;

            comboBox1.Items.Add(p1.name);

            */

           

            using(SqlConnection conn =newSqlConnection("Data source=凡斌-VAIO;Initialcatalog=DBPromary;integrated security=true"))

            {

                conn.Open();

                using(SqlCommand cmd = conn.CreateCommand())

                {

                    cmd.CommandText = "select * from promary";

                    using(SqlDataReader reader = cmd.ExecuteReader())

                    {

                        while (reader.Read())

                        {

                            //string str =reader.GetString(reader.GetOrdinal("proName"));

                            //comboBox1.Items.Add(str);

                            Province  pv =new  Province();

                            //将comboBox1控件的DisplayMember属性设置为“ProvinceName”用来在comboBox1控件中显示ProvinceName属性的值

                           comboBox1.DisplayMember = "ProvinceName";

                            pv.ProvinceName =reader.GetString(reader.GetOrdinal("proName"));

                            pv.ProvinceID =reader.GetInt32(reader.GetOrdinal("proID"));

                            //虽然pv属于对象，把一个对象添加到ComboxBox1中，控件显示的值为对象的类名，但是在前面comboBox1.DisplayMember ="ProvinceName"处已经设置好控件要显示的为 Province类的ProvinceName值，所以添加进去的是pv对象的ProvinceName值

                            comboBox1.Items.Add(pv);                          

                        }                      

                    }

                }

            }

        }

 

        privatevoid comboBox1_SelectedIndexChanged(object sender,EventArgse)       //注意这里是comboBox1不是comboBox2

        {

            try

            {

                Province  tem = (Province) comboBox1.SelectedItem;

                int id = tem.ProvinceID;

 

                comboBox2.Items.Clear();

                using(SqlConnection conn =newSqlConnection("Data source=凡斌-VAIO;Initialcatalog=DBPromary;integrated security=true"))

                {

 

                    conn.Open();

                    using (SqlCommand cmd = conn.CreateCommand())

                    {

                        //查询city（市）表里的 proID与promary（省）表里proID相同的所有数据。

                        cmd.CommandText = "select * from city where proID =@id";

                        cmd.Parameters.Add(new SqlParameter("id", id));

                        SqlDataReader dr = cmd.ExecuteReader();

 

                        while(dr.Read())

                        {

                           comboBox2.Items.Add(dr.GetString(dr.GetOrdinal("cityName")));

                        }

                    }

 

                }

            }

            catch(Exception ex)

            {

                MessageBox.Show("错误信息：" + ex.Message);

            }

        }

      

           

 

        }

   

    class Province

    {

        public string ProvinceName { get;set; }

        public int ProvinceID { get;set; }

    }

    //class People

    //{

    //   public string name { get; set; }

    //   public int age { get; set; }

    //}

}