实现二级联动菜单 C#，带完整数据库 SQL

----------------db.cs------------------------------

   // TODO: 在此处添加构造函数逻辑
   //
  }
  public static SqlConnection createConnection()
 {
 SqlConnection con=new SqlConnection("server=.;database=list;uid=sa;pwd=;");
   return con;
 }
 }
}


--------------------------.cs源文件--------------------------------

private void Page_Load(object sender, System.EventArgs e)
  {
   if(!Page.IsPostBack)
   {
    SqlConnection con=db.createConnection();
    con.Open();
    SqlCommand cmd=new SqlCommand("select * from sheng",con);
    SqlDataReader sdr=cmd.ExecuteReader();
    this.sheng.DataSource=sdr;
    this.sheng.DataTextField="sheng";
    this.sheng.DataValueField="shengid";
    this.sheng.DataBind();
    sdr.Close();
    cmd.CommandText="select * from city where shengid=1";
    sdr=cmd.ExecuteReader();
    this.city.DataSource=sdr;
    this.city.DataTextField="cityname";
    this.city.DataValueField="cityid";
    this.city.DataBind();
    sdr.Close();
    con.Close();
   }
  }
  #region Web 窗体设计器生成的代码
  override protected void OnInit(EventArgs e)
  {
   //
   // CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
   //
   InitializeComponent();
   base.OnInit(e);
  }
  
  /// <summary>
  /// 设计器支持所需的方法 - 不要使用代码编辑器修改
  /// 此方法的内容。
  /// </summary>
  private void InitializeComponent()
  {   
   this.sheng.SelectedIndexChanged += new System.EventHandler(this.DropDownList1_SelectedIndexChanged);
   this.Button1.Click += new System.EventHandler(this.Button1_Click);
   this.Calendar1.SelectionChanged += new System.EventHandler(this.Calendar1_SelectionChanged);
   this.rdl.SelectedIndexChanged += new System.EventHandler(this.drl_SelectedIndexChanged);
   this.mar.SelectedIndexChanged += new System.EventHandler(this.mar_SelectedIndexChanged);
   this.Load += new System.EventHandler(this.Page_Load);

  }
  #endregion

  private void Button1_Click(object sender, System.EventArgs e)
  {
   
  }
  private void DropDownList1_SelectedIndexChanged(object sender, System.EventArgs e)
  {
   SqlConnection con=db.createConnection();
   con.Open();
   SqlCommand cmd=new SqlCommand("select * from city where shengid="+this.sheng.SelectedValue.ToString(),con);
   SqlDataReader sdr=cmd.ExecuteReader();
   this.city.DataSource=sdr;
   this.city.DataTextField="cityname";
   this.city.DataValueField="cityid";
   this.city.DataBind();
   sdr.Close();
   con.Close();
  }

-----------------------sql文件-----------------------

create database list

use list

create table sheng
(
 shengid int primary key,
 sheng varchar(50) not null,
)

insert into sheng values(1,'四川')
insert into sheng values(2,'安徽')
insert into sheng values(3,'河南')
insert into sheng values(4,'重庆')
insert into sheng values(5,'广西')

select * from sheng

create table city
(
 cityid int primary key,
 shengid int foreign key references sheng(shengid),
 cityname varchar(50) not null,
)

insert into city values(1,1,'成都')
insert into city values(2,1,'绵阳')
insert into city values(3,1,'广元')
insert into city values(4,2,'合肥')
insert into city values(5,2,'蚌埠')
insert into city values(6,2,'淮南')
insert into city values(7,3,'郑州')
insert into city values(8,3,'开封')
insert into city values(10,3,'商丘')
insert into city values(11,4,'垫江')
insert into city values(12,4,'江津')
insert into city values(13,4,'重庆')
insert into city values(14,5,'南宁')
insert into city values(15,5,'柳州')
insert into city values(16,5,'白色')

select * from city

---------如果有朋友学习要用的话最好看清楚，呵呵，我是边做边写的，并不是可以一次执行成功的------