下拉框 DropDownList 问个问题

Question

 当DropDownList1 文本框里的值变动，DropDownList2值就根据 DropDownList1 查询数据！我不知道我的表达对不对
！ 是那个事件！ 我要怎么操作@
也就是说 DropDownList1 文本是 院区  DropDownList2 就显示 院区下面的科室！ 

Answer 1

        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);
        }        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();        }
这个可以参考下

Answer 2

             L_YuanQu_server lyuu = new L_YuanQu_server();
            DataTable dt = lyuu.getdropyuu();
            this.DropDownList1.DataSource = dt;
            this.DropDownList1.DataTextField = "name";
            this.DropDownList1.DataValueField = "id";
            this.DropDownList1.DataBind();
我把这个 放到我的DropDownList1_SelectedIndexChanged对吗

Answer 3

L_YuanQu_server lyuu = new L_YuanQu_server();
  DataTable dt = lyuu.getdropyuu();
  this.DropDownList1.DataSource = dt;
  this.DropDownList1.DataTextField = "name";
  this.DropDownList1.DataValueField = "id";
  this.DropDownList1.DataBind();你这个是绑定 DropDownList1 的数据源
你应该在DropDownList1_SelectedIndexChanged
事件里 根据DropDownList1的value来查询出数据 绑定到DropDownList2很典型的下拉框联动  坛子里一搜很多的