一个表三级联动---WinFrom

  1 using System;
  2 using System.Collections.Generic;
  3 using System.ComponentModel;
  4 using System.Data;
  5 using System.Data.SqlClient;
  6 using System.Drawing;
  7 using System.Linq;
  8 using System.Text;
  9 using System.Threading.Tasks;
 10 using System.Windows.Forms;
 11  
 12 namespace rr
 13 {
 14     public partial class Form1 : Form
 15     {
 16         public Form1()
 17         {
 18             InitializeComponent();
 19         }
 20         private void Fill1()
 21         {
 22             List<ChinaStates> list = new ChinaStatesDA().Select("0001");
 23             comboBox1.DataSource = list;
 24             comboBox1.DisplayMember = "AreaName";
 25             comboBox1.ValueMember = "AreaCode";
 26         }
 27         private void Fill2()
 28         {
 29  
 30             string parentcode="";
 31             if (comboBox1.SelectedItem!=null)
 32             {
 33                             parentcode = (comboBox1.SelectedItem as ChinaStates).AreaCode;
 34  
 35             }
 36  
 37             List<ChinaStates> list = new ChinaStatesDA().Select(parentcode);
 38             comboBox2.DataSource = list;
 39             comboBox2.DisplayMember = "AreaName";
 40             comboBox2.ValueMember = "AreaCode";
 41  
 42         }
 43         private void Fill3()
 44         {
 45             string parentcode = "";
 46             if (comboBox2.SelectedItem != null)
 47             {
 48                 parentcode = (comboBox2.SelectedItem as ChinaStates).AreaCode;
 49  
 50             }
 51             List<ChinaStates> list = new ChinaStatesDA().Select(parentcode);
 52             comboBox3.DataSource = list;
 53             comboBox3.DisplayMember = "AreaName";
 54             comboBox3.ValueMember = "AreaCode";
 55  
 56         }
 57         private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
 58         {
 59  
 60             Fill3();
 61         }
 62  
 63         private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
 64         {
 65             Fill2();
 66             Fill3();
 67         }
 68  
 69         private void Form1_Load(object sender, EventArgs e)
 70         {
 71             Fill1();
 72             Fill2();
 73             Fill3();
 74         }
 75     }
 76     class DBcon
 77     {
 78         public const string CONSTR = "server=.;database=yy;uid=sa;pwd=111111";
 79     }
 80     class ChinaStates
 81     {
 82         public string AreaCode { get; set; }
 83         public string AreaName { get; set; }
 84         public string ParentCode { get; set; }
 85     }
 86     class ChinaStatesDA
 87     {
 88         private SqlConnection Con;
 89         private SqlCommand Cmd;
 90         private SqlDataReader dr;
 91         public ChinaStatesDA()
 92         {
 93             Con = new SqlConnection(DBcon.CONSTR);
 94             Cmd = Con.CreateCommand();
 95         }
 96         public List<ChinaStates> Select(string code)
 97         {
 98             List<ChinaStates> list = new List<ChinaStates>();
 99             Cmd.CommandText = "select * from ChinaStates where ParentAreaCode=@code";
100             Cmd.Parameters.Clear();
101             Cmd.Parameters.AddWithValue("@code", code);
102             try
103             {
104                 Con.Open();
105                 dr = Cmd.ExecuteReader();
106                 while (dr.Read())
107                 {
108                     ChinaStates data = new ChinaStates();
109                     data.AreaCode = dr["AreaCode"].ToString();
110                     data.AreaName = dr["AreaName"].ToString();
111                     data.ParentCode = dr["ParentAreaCode"].ToString();
112                     list.Add(data);
113                 }
114             }
115             finally
116             {
117                 Con.Close();
118             }
119  
120  
121             return list;
122         }
123     }
124 }