not firing dropdownlist without autopostback

Question

hello everyone 

 

i want to firing my dropdownlist without autopostback, this is possible,

 

below my code

 

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
                                                <ContentTemplate>
                                                    <asp:DropDownList ID="ddlIndustry" runat="server" OnSelectedIndexChanged="ddlIndustry_SelectedIndexChanged"></asp:DropDownList>
                                                </ContentTemplate>
                                                <Triggers>
                                                    <asp:AsyncPostBackTrigger ControlID="ddlIndustry" EventName="SelectedIndexChanged" />
                                                </Triggers>
                                            </asp:UpdatePanel>

protected void ddlIndustry_SelectedIndexChanged(object sender, EventArgs e)
    {

        StringBuilder builder = new StringBuilder();

        string sqlQueryOcc = "select SALARY_INDS_OCCNAME.INDUS_CAT_VAL,SALARY_INDS_OCCNAME.INDUS_CAT_NAME,SALARY_INDS_OCCNAME.INDUS_CAT_CODE from SALARY_INDS_OCCNAME ";
        sqlQueryOcc += " inner join SALARY_INDS";
        sqlQueryOcc += " on SALARY_INDS_OCCNAME.INDUS_CODE = SALARY_iNDS.INDUS_CODE ";
        sqlQueryOcc += " where SALARY_INDS.INDUS_CODE = '" + ddlIndustry.SelectedValue + "'";
        using (SqlCommand cmd = new SqlCommand(sqlQueryOcc))
        {
            cmd.CommandType = CommandType.Text;
            cmd.Connection = conn;
            conn.Open();
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            da.Fill(dt);
            foreach (DataRow row in dt.Rows)
            {
                builder.AppendFormat("<li><span><input type='checkbox' name='sel_items[]' value='{0}' /></span>{1}</li>", row["INDUS_CAT_CODE"].ToString(), row["INDUS_CAT_NAME"].ToString());
            }
            conn.Close();

        }
  this.occList.Text = builder.ToString();
    }