web服务器控件

Question

寻找实现DropDownList的三级联动的主要代码：

Answer 1

protected void Page_Load(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                
                ddlBindPro();
            }
        }        //绑定省
        public void ddlBindPro()
        {
            Common_Bll com = new Common_Bll();
            DataTable dt = null;
            dt = com.GetProvince();
            if (dt.Equals(null))
            {
                this.ddlProvince.Items.Add(new ListItem("请选择省", "0"));            }
            else
            {
                this.ddlProvince.Items.Add(new ListItem("请选择省", "0"));
                this.ddlProvince.DataSource = dt;
                this.ddlProvince.DataTextField = "Province_Name";
                this.ddlProvince.DataValueField = "Province_ID";
                this.ddlProvince.DataBind();
            }        }        //绑定地区
        //public void ddlBindCity(string _provinceid)
        //{        //    string strSelect = "select City_ID,City_name from City where Province_ID='" + _provinceid + "'";
        //    DbHelper db = new DbHelper();
        //    this.ddlCity.DataSource = db.ExecuteDataTable(db.GetSqlStringCommond(strSelect));
        //    this.ddlCity.DataTextField = "City_name";
        //    this.ddlCity.DataValueField = "City_Id";
        //    this.ddlCity.DataBind();        //}        //绑定城市
        //public void ddlBindCounty(string _cityid)
        //{        //    string strSelect = "select Country_ID,Country_Name from Country where City_ID='" + _cityid + "'";
        //    DbHelper db = new DbHelper();
        //    this.ddlCounty.DataSource = db.ExecuteDataTable(db.GetSqlStringCommond(strSelect));
        //    this.ddlCounty.DataTextField = "Country_Name";
        //    this.ddlCounty.DataValueField = "Country_ID";
        //    this.ddlCounty.DataBind();        //}        //protected void ddlCity_SelectedIndexChanged(object sender, EventArgs e)
        //{
        //    for (int i = 0; i < this.ddlCounty.Items.Count; i++)
        //    {        //        this.ddlCounty.Items.RemoveAt(i);        //    }        //    string Cityid = this.ddlCity.SelectedValue;
        //    ddlBindCounty(Cityid);        //}        //protected void ddlProvince_SelectedIndexChanged(object sender, EventArgs e)
        //{
        //    for (int i = this.ddlCity.Items.Count - 1; i >= 0; i--)
        //    {        //        this.ddlCity.Items.RemoveAt(i);        //    }
        //    for (int i = this.ddlCounty.Items.Count - 1; i >= 0; i--)
        //    {        //        this.ddlCounty.Items.RemoveAt(i);
        //    }
        //    string ProvinceId = this.ddlProvince.SelectedValue;
        //    ddlBindCity(ProvinceId);
        //}

Answer 2

DropDownList联动（经典）
DropDownList用JQuery实现Ajax三级联动