ASP頁面中的三級聯動，載入資料

ASP頁面上：

卡類別：<asp:DropDownList ID="DropDownList_cardType1" runat="server"                               AutoPostBack="True"                               onselectedindexchanged="DropDownList_cardType1_SelectedIndexChanged"                              DataTextField="TypeName" DataValueField="TypeNum"></asp:DropDownList>                         <asp:DropDownList ID="DropDownList_cardType2" runat="server"                              AutoPostBack="True"                               onselectedindexchanged="DropDownList_cardType2_SelectedIndexChanged"                              DataTextField="TypeName" DataValueField="TypeNum"></asp:DropDownList>                         <asp:DropDownList ID="DropDownList_cardType3" runat="server"                              DataTextField="TypeName" DataValueField="TypeNum"></asp:DropDownList>

第一個和第二個下拉框要設定AutoPostBack = "true"

C#後台代碼：

#region _____________載入資料_____卡類型____________            //卡類型            string typeSql = "select distinct TypeNum,TypeName from tbl_CardTypeNew where TypeLevel = '1'";            DataSet ds2 = DBFhkHelper.queryDB(typeSql);            if (!IsPostBack)            {                if (ds2.Tables[0].Rows.Count > 0)                {                    DataTable table1 = new DataTable();                    table1.Columns.Add("TypeNum");                    table1.Columns.Add("TypeName");                    DataRow drNew = table1.NewRow();                    drNew["TypeName"] = "-全部-";                    drNew["TypeNum"] = "-全部-";                    table1.Rows.Add(drNew);                    table1.Merge(ds2.Tables[0]);                    DropDownList_cardType1.DataSource = table1;                    DropDownList_cardType1.DataBind();                    DropDownList_cardType1.SelectedIndex = 0;                }                //第二個類型                DataTable table2 = new DataTable();                table2.Columns.Add("TypeNum");                table2.Columns.Add("TypeName");                DataRow drNew2 = table2.NewRow();                drNew2["TypeName"] = "-全部-";                drNew2["TypeNum"] = "-全部-";                table2.Rows.Add(drNew2);                DropDownList_cardType2.DataSource = table2;                DropDownList_cardType2.DataBind();                DropDownList_cardType2.SelectedIndex = 0;                //第三個類型                DropDownList_cardType3.DataSource = table2;                DropDownList_cardType3.DataBind();                DropDownList_cardType3.SelectedIndex = 0;            }            #endregion _____________載入資料_________________

第一個下拉框選擇事件，要載入第二個下拉框的資料。

c#代碼如下：

  #region 選擇一級卡類別之後，載入二級卡類別        protected void DropDownList_cardType1_SelectedIndexChanged(object sender, EventArgs e)        {            DropDownList_cardType2.DataSource = null;            DropDownList_cardType3.DataSource = null;            //三級卡類別            DataTable table2 = new DataTable();            table2.Columns.Add("TypeNum");            table2.Columns.Add("TypeName");            DataRow drNew2 = table2.NewRow();            drNew2["TypeName"] = "-全部-";            drNew2["TypeNum"] = "-全部-";            table2.Rows.Add(drNew2);            DropDownList_cardType3.DataSource = table2;            DropDownList_cardType3.DataBind();            DropDownList_cardType3.SelectedIndex = 0;            string type1 = DropDownList_cardType1.SelectedValue.ToString();//01-類型名稱                        if (type1 != "-全部-")            {                  //根據一級卡類別的編號查詢二級卡類別                string querySql = "select TypeNum,TypeName from tbl_CardTypeNew where UpLNum = '" + type1 + "' and TypeLevel='2' ";                  DataSet ds2 = DBFhkHelper.queryDB(querySql);                  if (ds2.Tables[0].Rows.Count > 0)                  {                      DataTable table1 = new DataTable();                      table1.Columns.Add("TypeNum");                      table1.Columns.Add("TypeName");                      DataRow drNew = table1.NewRow();                      drNew["TypeName"] = "-全部-";                      drNew["TypeNum"] = "-全部-";                      table1.Rows.Add(drNew);                      table1.Merge(ds2.Tables[0]);                      DropDownList_cardType2.DataSource = table1;                      DropDownList_cardType2.DataBind();                      DropDownList_cardType2.SelectedIndex = 0;                  }                  else                  {                      //二級卡類別                      DataTable table3 = new DataTable();                      table3.Columns.Add("TypeNum");                      table3.Columns.Add("TypeName");                      DataRow drNew3 = table3.NewRow();                      drNew3["TypeName"] = "-全部-";                      drNew3["TypeNum"] = "-全部-";                      table3.Rows.Add(drNew3);                      DropDownList_cardType2.DataSource = table3;                      DropDownList_cardType2.DataBind();                      DropDownList_cardType2.SelectedIndex = 0;                  }            }            else            {                //二級卡類別                DataTable table3 = new DataTable();                table3.Columns.Add("TypeNum");                table3.Columns.Add("TypeName");                DataRow drNew3 = table3.NewRow();                drNew3["TypeName"] = "-全部-";                drNew3["TypeNum"] = "-全部-";                table3.Rows.Add(drNew3);                DropDownList_cardType2.DataSource = table3;                DropDownList_cardType2.DataBind();                DropDownList_cardType2.SelectedIndex = 0;            }        }        #endregion 選擇一級卡類別之後，載入二級卡類別

第二個下拉框選擇事件，載入第三個下拉框的資料：

 #region 選擇二級卡類別之後，載入三級卡類別        protected void DropDownList_cardType2_SelectedIndexChanged(object sender, EventArgs e)        {            DropDownList_cardType3.DataSource = null;            string type2 = DropDownList_cardType2.SelectedValue.ToString();//0102-類型名稱            if (type2 != "-全部-")            {                //根據二級卡類別的編號查詢三級卡類別                string querySql = "select TypeNum,TypeName from tbl_CardTypeNew where UpLNum = '" + type2 + "' and TypeLevel='3' ";                DataSet ds2 = DBFhkHelper.queryDB(querySql);                if (ds2.Tables[0].Rows.Count > 0)                {                    DataTable table1 = new DataTable();                    table1.Columns.Add("TypeNum");                    table1.Columns.Add("TypeName");                    DataRow drNew = table1.NewRow();                    drNew["TypeName"] = "-全部-";                    drNew["TypeNum"] = "-全部-";                    table1.Rows.Add(drNew);                    table1.Merge(ds2.Tables[0]);                    DropDownList_cardType3.DataSource = table1;                    DropDownList_cardType3.DataBind();                    DropDownList_cardType3.SelectedIndex = 0;                }                else                {                    //三級卡類別                    DataTable table3 = new DataTable();                    table3.Columns.Add("TypeNum");                    table3.Columns.Add("TypeName");                    DataRow drNew3 = table3.NewRow();                    drNew3["TypeName"] = "-全部-";                    drNew3["TypeNum"] = "-全部-";                    table3.Rows.Add(drNew3);                    DropDownList_cardType3.DataSource = table3;                    DropDownList_cardType3.DataBind();                    DropDownList_cardType3.SelectedIndex = 0;                }            }            else            {                //三級卡類別                DataTable table3 = new DataTable();                table3.Columns.Add("TypeNum");                table3.Columns.Add("TypeName");                DataRow drNew3 = table3.NewRow();                drNew3["TypeName"] = "-全部-";                drNew3["TypeNum"] = "-全部-";                table3.Rows.Add(drNew3);                DropDownList_cardType3.DataSource = table3;                DropDownList_cardType3.DataBind();                DropDownList_cardType3.SelectedIndex = 0;            }        }        #endregion 選擇二級卡類別之後，載入三級卡類別