我在頁面上有2個dropdownlist控件,我希望另外一個dropdownlist的內容取決于另外一個的選擇,  protected void ddpM_Type_SelectedIndexChanged(object sender, EventArgs e){  string strWhere = "DelFlag = 'false'";           if (this.ddpM_People.SelectedValue == "內部維修")            {                ddpM_Company.Items.Clear();                ddpM_Company.DataTextField = "Dept_Name";                ddpM_Company.DataValueField = "Dept_ID";                bindList(ddpM_Company, department.GetList(strWhere).Tables[0]);                           }            if (this.ddpM_People.SelectedValue == "外委維修")            {                ddpM_Company.Items.Clear();                ddpM_Company.DataTextField = "C_Name";                ddpM_Company.DataValueField = "C_ID";                bindList(ddpM_Company, corporations.GetList(strWhere).Tables[0]);                          }}但是這樣沒效果,我dropdownlist里面的內容是從數據庫中讀取的,請問如何實現聯動啊?