dropdownlist级联问题

Question

if (!IsPostBack)
        {  //绑定dropdownlist里面的值
                string conn = ConfigurationManager.ConnectionStrings["connectionString"].ConnectionString;
                SqlConnection connection = new SqlConnection(conn);
                connection.Open();
                string Login = Session["Login"].ToString();
                string sqlSelectProject = "select distinct ProjectName from TaskName where TaskManage='" + Login + "'";
                SqlDataAdapter daAdmin = new SqlDataAdapter(sqlSelectProject, connection);
                DataSet dsAdmin = new DataSet();
                daAdmin.Fill(dsAdmin);
                DropDownList1.DataValueField = "ProjectName";
                DropDownList1.DataTextField = "ProjectName";
                DropDownList1.DataSource = dsAdmin;
                DropDownList1.DataBind();
                daAdmin.Dispose();
                dsAdmin.Dispose();
                connection.Close();
            }//然后我在SelectedIndexChanged里面写
 protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        string conn = ConfigurationManager.ConnectionStrings["connectionString"].ConnectionString;
        SqlConnection connection = new SqlConnection(conn);
        connection.Open();
        string Login = Session["Login"].ToString();
//根据dropdownlist1里面的值进行判断
        string sqlTask = "select TaskName from TaskName where TaskManage='" + Login + "' and ProjectName='" +
                 DropDownList1.Text + "'";
        SqlDataAdapter daTaskInfo = new SqlDataAdapter(sqlTask, connection);
        DataSet dsTaskInfo = new DataSet();
        daTaskInfo.Fill(dsTaskInfo);
        DropDownList2.DataValueField = "TaskName";
        DropDownList2.DataTextField = "TaskName";
        DropDownList2.DataBind();
        daTaskInfo.Dispose();
        dsTaskInfo.Dispose();
    }
可是这样为什么没有效果呢？

Answer 1

调试看看 DropDownList1_SelectedIndexChanged 执行了没

Answer 2

执行的，我在下面加个write语句是显示的。

Answer 3

而且dropdownlist1的值也是取到的，可是dropdownlist2就是不显示

Answer 4

现在是什么问题呢  DropDownList2数据没绑定上？

Answer 5

调试看看 dsTaskInfo 里有数据么

Answer 6

没有数据肯定不显示啊  看看是不是sql语句 有问题 

Answer 7

晕， 我忘记写这个了：DropDownList2.DataSource = dsTaskInfo;