1.首先封装操作数据库的类SqlHelper，当然前提还得创建数据库连接
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Configuration; using System.Data.SqlClient; namespace 省市联动 { public class SqlHelper { private static readonly string str = ConfigurationManager.ConnectionStrings["conStr"].ConnectionString; //封装三个方法 /// <summary> /// 此方法可以做增删改 /// </summary> /// <param name="sql">sql语句</param> /// <param name="ps">sql语句中的参数</param> /// <returns>返回受影响的行数，int类型</returns> public static int ExecuteNonQuery(string sql,params SqlParameter[] ps) { //连接数据库 using (SqlConnection con=new SqlConnection(str)) { using (SqlCommand cmd=new SqlCommand(sql,con)) { con.Open(); if (ps!=null) { cmd.Parameters.AddRange(ps); } return cmd.ExecuteNonQuery(); } } } /// <summary> /// 该方法用在查询上 /// </summary> /// <param name="sql">sql语句</param> /// <param name="ps">sql语句中的参数</param> /// <returns>首行首列，object类型</returns> public static object ExecuteSclar(string sql,params SqlParameter[] ps) { using (SqlConnection con=new SqlConnection(str)) { using (SqlCommand cmd=new SqlCommand(sql,con)) { con.Open(); if (ps != null) { cmd.Parameters.AddRange(ps); } return cmd.ExecuteScalar(); } } } /// <summary> /// 该方法用于查询读数据 /// </summary> /// <param name="sql">sql语句</param> /// <param name="ps">sql语句中的参数</param> /// <returns>返回的是SqlDataReader对象,里面有数据</returns> public static SqlDataReader ExecuteReader(string sql,params SqlParameter[] ps) { SqlConnection con = new SqlConnection(str); using (SqlCommand cmd=new SqlCommand(sql,con)) { if (ps!=null) { cmd.Parameters.AddRange(ps); } try { con.Open(); return cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection); } catch (Exception ex) { con.Close(); con.Dispose(); throw ex; } } } } }2.修改App.config中的内容，做好准备
<?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> </configSections> <connectionStrings> <add name="conStr" connectionString="Data Source=LENOVO-PC;Initial Catalog=MyDatabase;Integrated Security=True" /> <add name="省市联动.Properties.Settings.MyDatabaseConnectionString" connectionString="Data Source=LENOVO-PC;Initial Catalog=MyDatabase;Persist Security Info=True;User ID=sa;Password=pingxing9132" providerName="System.Data.SqlClient" /> </connectionStrings> <startup> <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6" /> </startup> </configuration>3.添加引用，右键项目下的引用，添加引用，程序集，System.Configuration,确定 4.窗体设计如下 5.窗体代码
using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; using System.Data.SqlClient; namespace 省市联动 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } int r = -1;//判断标志,全局变量 private void Form1_Load(object sender, EventArgs e) { // TODO: 这行代码将数据加载到表“myDatabaseDataSet2.S_District”中。您可以根据需要移动或删除它。 this.s_DistrictTableAdapter1.Fill(this.myDatabaseDataSet2.S_District); // TODO: 这行代码将数据加载到表“myDatabaseDataSet1.S_District”中。您可以根据需要移动或删除它。 this.s_DistrictTableAdapter.Fill(this.myDatabaseDataSet1.S_District); // TODO: 这行代码将数据加载到表“myDatabaseDataSet.S_City”中。您可以根据需要移动或删除它。 this.s_CityTableAdapter.Fill(this.myDatabaseDataSet.S_City); r = 1; LoadAreaByAreaId(0); } private void LoadAreaByAreaId(int p) { List<Area> list = new List<Area>(); if (r == 1)//窗体加载时显示省份 { list.Clear(); list.Add(new Area() { Id = -1, Name = "请选择" });//只是在集合存在，在数据库中是不存在的，查询不到的 string sql = "select ProvinceID,Provincename from .S_Province where AreaId=" + p; using (SqlDataReader reader = SqlHelper.ExecuteReader(sql)) { if (reader.HasRows) { while (reader.Read()) { Area a = new Area(); a.Id = Convert.ToInt32(reader["ProvinceID"]); a.Name = reader["ProvinceName"].ToString(); list.Add(a); } } } cmbProvince.DataSource = list; cmbProvince.DisplayMember = "Name";//设置要显示的属性 cmbProvince.ValueMember = "Id";//设置要显示的属性隐藏的值 /* 实际上在Combox中显示的值是表面的，在内存中存在的是前面的id 数字，意思就是说，Combox中显示的是Name，而在内存中存储的是Id，将 来如果用cmbProvince.SelectedValue拿到的值就是Id的值。 */ } else if (r==2)//点击显示城市 { list.Clear(); list.Add(new Area() { Id = -1, Name = "请选择" }); string sql = "select CityID,CityName from .S_City where ProvinceID="+p; using (SqlDataReader reader=SqlHelper.ExecuteReader(sql)) { if (reader.HasRows) { while (reader.Read()) { Area b = new Area(); b.Id = Convert.ToInt32(reader["CityID"]); b.Name = reader["CityName"].ToString(); list.Add(b); } } } cmbCity.DataSource = list; cmbCity.DisplayMember = "Name"; cmbCity.ValueMember = "Id"; listBox1.DataSource = list; listBox1.DisplayMember = "Name"; } else { list.Clear(); list.Add(new Area() { Id = -1, Name = "请选择" }); string sql = "select DistrictID,DistrictName from .S_District where CityID="+p; using (SqlDataReader reader=SqlHelper.ExecuteReader(sql)) { if (reader.HasRows) { while (reader.Read()) { Area c = new Area(); c.Id = Convert.ToInt32(reader["DistrictID"]); c.Name = reader["DistrictName"].ToString(); list.Add(c); } } } cmbDistrict.DataSource = list; cmbDistrict.DisplayMember = "Name"; cmbDistrict.ValueMember = "Id"; listBox2.DataSource = list; listBox2.DisplayMember = "Name"; listBox2.ValueMember = "Id"; } } private void cmbProvince_SelectedIndexChanged(object sender, EventArgs e) { r = 2; if (cmbProvince.SelectedIndex != 0)//刚开始的值是类 { int selectValue = Convert.ToInt32(cmbProvince.SelectedValue); LoadAreaByAreaId(selectValue); } } private void cmbCity_SelectedIndexChanged(object sender, EventArgs e) { r = 3; if (cmbCity.SelectedIndex != 0) { int selectValue = Convert.ToInt32(cmbCity.SelectedValue); LoadAreaByAreaId(selectValue); } } } }