winform窗体 小程序【三级联动】

三级联动[省,市,区]

类似地区选择，当选的某个省份，后面的下拉框相对变成对应省份的区县

实现省市区联动关键是数据库的表,[每个省内区的AreaCode列是同样的]

public Form2()
        {
            InitializeComponent();

            //绑定省
            comboBox1.DataSource = new ChinaData().Select("");
            comboBox1.DisplayMember = "AreaName";
            comboBox1.ValueMember = "AreaCode";

            //绑定市
            comboBox2.DataSource = new ChinaData().Select(comboBox1.SelectedValue.ToString());
            comboBox2.DisplayMember = "AreaName";
            comboBox2.ValueMember = "AreaCode";

            //绑定区县
            comboBox3.DataSource = new ChinaData().Select(comboBox2.SelectedValue.ToString());
            comboBox3.DisplayMember = "AreaName";
            comboBox3.ValueMember = "AreaCode";

        }

          // 当省列表选项改变时  绑定相应的市
        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {

            comboBox2.DataSource = new ChinaData().Select(comboBox1.SelectedValue.ToString());
            comboBox2.DisplayMember = "AreaName";
            comboBox2.ValueMember = "AreaCode";
        }

        // 当市列表选项改变时  绑定相应的区县
        private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
        {

            comboBox3.DataSource = new ChinaData().Select(comboBox2.SelectedValue.ToString());
            comboBox3.DisplayMember = "AreaName";
            comboBox3.ValueMember = "AreaCode";
        }