c# - 想解绑下拉列表？

Question

我创建了 web 应用程序，因为我想使用两个下拉列表。当我从 dropdown1 中选择一些值时，它会影响 dropdown2，但是第一次绑定(bind)的值不清楚，有人能帮帮我吗

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        Select sel_obj = new Select();
        #region Load Department Name
        if (departchk.Checked==true && DropDownList1.SelectedIndex==1)
        {

            DataTable DT = sel_obj.select_Dept_Name();
            recordddl.DataSource = DT;
            recordddl.DataTextField = "Department_Name";
            //departmentDrop.DataValueField = "Department_ID";
            recordddl.DataBind();
            recordddl.Items.Insert(0, new ListItem("--Select--", "0"));
        }
        #endregion
        #region Load Employee Name
        else if(departchk.Checked==true && DropDownList1.SelectedIndex==2)
        {

            DataTable DS = sel_obj.select_Emp_Name();
            recordddl.DataSource = DS;
            recordddl.DataTextField = "Employee_Name";
            recordddl.DataBind();
            recordddl.Items.Insert(0, new ListItem("--Select--", "0"));
        }
        #endregion
        #region Load Location Name
        else if(departchk.Checked==true && DropDownList1.SelectedIndex==3)
        {
            DataTable DD2 = sel_obj.select_Location_Name();
            recordddl.DataSource = DD2;
            recordddl.DataTextField = "Location_Name";
            recordddl.DataBind();
            recordddl.Items.Insert(0, new ListItem("--Select--", "0"));
        }
        #endregion
    }

Answer 1

就像DropDownList1.Items.Clear();一样简单

Check a complete example here