一、如下comboBox1、comboBox2、comboBox3，原来这三个都是空的，
将数据库中的省份传递到comboBox1中
我的数据库有parent字段，根据市的parent找到省，根据县的找到市，所以下面的sql语句在省市县联动时，sql语句是一样的
二、代码
1、在Load方法中，加载省份(根据需求变换sql语句)
private void Form1_Load(object sender, EventArgs e) { using (SQLiteConnection con = new SQLiteConnection(Constants.DATA_SOURCE)) { con.Open(); using (SQLiteCommand cmd = new SQLiteCommand()) { cmd.Connection = con; cmd.CommandText = string.Format("select * from test t where t.[district_level]=2"); int rows = cmd.ExecuteNonQuery(); SQLiteDataAdapter sda = new SQLiteDataAdapter(cmd); DataTable dt = new DataTable(); sda.Fill(dt); comboBox1.DataSource = dt; comboBox1.DisplayMember = "name"; comboBox1.ValueMember="id"; } } } (1)、用sql命令查询要在comboBox中显示的值
(2)、将值给DataTable
(3)、DisplayMember 就是要显示的数据库中的字段：name
(4)、ValueMember：一般是数据库中的主键：id
2、进入comboBox1事件，根据省份，显示市
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e) { if (comboBox1.SelectedIndex > -1) { DataRowView drv = (DataRowView)comboBox1.SelectedItem; string id = drv.Row["id"].ToString();//获得已绑定的选项的id using (SQLiteConnection con = new SQLiteConnection(Constants.DATA_SOURCE)) { con.Open(); using (SQLiteCommand cmd = new SQLiteCommand()) { cmd.Connection = con; cmd.CommandText = string.Format("select * from test t where t.[parent]='" + id + "'"); int rows = cmd.ExecuteNonQuery(); SQLiteDataAdapter sda = new SQLiteDataAdapter(cmd); DataTable dt = new DataTable(); sda.Fill(dt); comboBox2.DataSource = dt; comboBox2.DisplayMember = "name"; comboBox2.ValueMember = "id"; } } } }
3、进入comboBox2事件，根据市，显示县
private void comboBox2_SelectedIndexChanged(object sender, EventArgs e) { if (comboBox2.SelectedIndex > -1) { DataRowView drv = (DataRowView)comboBox2.SelectedItem; string id = drv.Row["id"].ToString();//获得id using (SQLiteConnection con = new SQLiteConnection(Constants.DATA_SOURCE)) { con.Open(); using (SQLiteCommand cmd = new SQLiteCommand()) { cmd.Connection = con; cmd.CommandText = string.Format("select * from test t where t.[parent]='" + id + "'"); int rows = cmd.ExecuteNonQuery(); SQLiteDataAdapter sda = new SQLiteDataAdapter(cmd); DataTable dt = new DataTable(); sda.Fill(dt); comboBox3.DataSource = dt; comboBox3.DisplayMember = "name"; comboBox3.ValueMember = "id"; } } } }
三、 结果：
四 、有的省没有县，县是空值时，联动会出现异常，上一次联动的县的值还在显示，
点击县时，因为县的下一级没有值，显示的还是上次联动的结果，其实它并没有处于选中状态，只是显示出来了
所以，处理一下，因为没有处于选中状态，所以SelectedIndex是-1
if(comboBox3.SelectedIndex!=0){ comboBox3.Text = "";}
五、其他：
1、如果一个页面有多条这样的省市县联动
把上面的步骤再来一遍即可,只是Load里需要注意，不能图省事把comboBox4直接加在comboBox1后，否则点下面的省份，上面的也会变
using (SQLiteConnection con = new SQLiteConnection(Constants.DATA_SOURCE)) { con.Open(); using (SQLiteCommand cmd = new SQLiteCommand()) { cmd.Connection = con; cmd.CommandText = string.Format("select * from test where t.[district_level]=2"); int rows = cmd.ExecuteNonQuery(); SQLiteDataAdapter sda = new SQLiteDataAdapter(cmd); DataTable dt = new DataTable(); sda.Fill(dt); comboBox1.DataSource = dt; comboBox1.DisplayMember = "name"; comboBox1.ValueMember="id"; } } using (SQLiteConnection con = new SQLiteConnection(Constants.DATA_SOURCE)) { con.Open(); using (SQLiteCommand cmd = new SQLiteCommand()) { cmd.Connection = con; cmd.CommandText = string.Format("select * from test t where t.[district_level]=2"); int rows = cmd.ExecuteNonQuery(); SQLiteDataAdapter sda = new SQLiteDataAdapter(cmd); DataTable dt = new DataTable(); sda.Fill(dt); comboBox4.DataSource = dt; comboBox4.DisplayMember = "name"; comboBox4.ValueMember = "id"; } }
2、把comboBox1的事件代码封装成一个类DBDao.cs，方法名为getAddress()
（1）sql语句用的一样的时候(上面说的，根据市的parent找到省，根据县的parent找到市)，我把sql语句也封装了
public static void getAddress(ComboBox combo1, ComboBox combo2) { if (combo1.SelectedIndex > -1) { DataRowView drv = (DataRowView)combo1.SelectedItem; string id = drv.Row["id"].ToString();//获得id using (SQLiteConnection con = new SQLiteConnection(Constants.DATA_SOURCE)) { con.Open(); using (SQLiteCommand cmd = new SQLiteCommand()) { cmd.Connection = con; cmd.CommandText = string.Format("select t.* from test t where t.[parent]='" + id + "'"); int rows = cmd.ExecuteNonQuery(); SQLiteDataAdapter sda = new SQLiteDataAdapter(cmd); DataTable dt = new DataTable(); sda.Fill(dt); combo2.DataSource = dt; combo2.DisplayMember = "name"; combo2.ValueMember = "id"; } } } } 在comboBox1的点击事件中直接调用即可，
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e) { DBDao.getAddress(comboBox1, comboBox2); } private void comboBox2_SelectedIndexChanged(object sender, EventArgs e) { DBDao.getAddress(comboBox2, comboBox3); }
（2）sql语句不同的时候，不要把sql语句封装(留着以后用)
public static void ComboBoxLoad(string sql, ComboBox combobox) { using (SQLiteConnection con = new SQLiteConnection(Constants.DATA_SOURCE)) { con.Open(); using (SQLiteCommand cmd = new SQLiteCommand()) { cmd.Connection = con; cmd.CommandText = string.Format(sql); int rows = cmd.ExecuteNonQuery(); SQLiteDataAdapter sda = new SQLiteDataAdapter(cmd); DataTable dt = new DataTable(); sda.Fill(dt); combobox.DataSource = dt; combobox.DisplayMember = "name"; combobox.ValueMember = "id"; } } }
其他页面调用：
string sql="select * from test t where t.id='0302' order by t.code asc";DBDao.ComboBoxLoad(sql,comboBox12);
参考：
https://zhidao.baidu.com/question/242563101.html?qbl=relate_question_2&word=c%20combobox%BC%D3%D4%D8%CA%FD%BE%DD&skiptype=2