C#-WinForm-三级联动

三级联动 - 查询地区，选择省份自动显示该省份的市、区县

有如下一个数据库

　　

一、写查询方法

public class ChinaData

    {

        SqlConnection conn = null;

        SqlCommand cmd = null;

        public ChinaData()

        {

            conn = new SqlConnection("server=.;database=mydb;user=sa;pwd=123");

            cmd = conn.CreateCommand();

        }

        //查询方法 参数为父级代码

        public List<China> Select(string pcode)

        {

            List<China> lc = new List<China>();

            cmd.CommandText = "select *from ChinaStates where ParectAreaCode=@a";

            cmd.Parameters.Clear();

            cmd.Parameters.AddWithValue("@a",pcode);

            conn.Open();

            SqlDataReader dr = cmd.ExecuteReader();

            if (dr.HasRows)

            {

                while(dr.Read())

                {

                    China c = new China();

                    c.AreaCode = dr["AreaCode"].ToString();

                    c.AreaName = dr["AreaName"].ToString();

                    c.ParentAreaCode = dr["ParentAreaCode"].ToString();

                    lc.Add(c);

                }

            }

            conn.Close();

            return lc;

        }

    }

查询方法

二、窗体启动时自动读取数据库数据

 public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

            //窗口打开时，自动查询代码0001中国下的子级数据

            //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";

        }

    }

窗体启动时自动读取数据库数据

三、实现改变选项的时候，展示子级内容

//省选中项改变时事件

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)

        {

            //绑定市

            comboBox2.DataSource = new ChinaData().Select(comboBox1.SelectedValue.ToString());

            comboBox2.DisplayMember = "AreaName";

            comboBox2.ValueMember = "AreaCode";

        }

        //市选中项改变时事件

        private void comboBox2_SelectedIndexChanged_1(object sender, EventArgs e)

        {

            //绑定区县

            comboBox3.DataSource = new ChinaData().Select(comboBox2.SelectedValue.ToString());

            comboBox3.DisplayMember = "AreaName";

            comboBox3.ValueMember = "AreaCode";

        }

实现二级联动、三级联动

完成地区选择