本文实例讲述了C#用ComboBox控件实现省与市的联动效果的方法。分享给大家供大家参考。具体实现方法如下：

复制代码 代码如下: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; }
}
}

复制代码 代码如下:using System.Data.SqlClient;
namespace 省市选择2
{
public partial class Form1 : Form
{
publicForm1()
{
InitializeComponent();
}
privatevoid Form1_Load(objectsender,EventArgs e)
{

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; }
//}
}

如下图所示：

希望本文所述对大家的C#程序设计有所帮助。