将数据库值检索到没有重复值的数据绑定Dropdownlist的ASP.NET中

Question

每当用户单击"更新配置文件"按钮时，他将被引导到页面，在中，他在注册期间保存的所有信息都将显示在文本框中，并在页面加载后下拉列表。（下载列表是数据绑定的）

使用下面的代码，我可以做到这一点，但是，当我更改DDLDepartment（第一个下拉列表）中的值时，DDLGroup（第二个下拉列表

DDL部门和DDL组是相互关联的，因为DDL组根据在DDL部门中选择的值进行过滤

  protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack) // important
        {
            DataTable dt = new DataTable();
            con.Open();
            SqlDataReader myReader = null;

            string cmdstr = "SELECT * from USERSONLINE where Username = '" + Session["Username"] + "'";
            SqlCommand userExist = new SqlCommand(cmdstr, con);
            myReader = userExist.ExecuteReader();
            while (myReader.Read())
            {
                txtEmpID.Text = (myReader["EmpId"].ToString());
                txtFirstName.Text = (myReader["FirstName"].ToString());
                txtLastName.Text = (myReader["LastName"].ToString());
                txtUsername.Text = (myReader["Username"].ToString());
                ddlDepartment.SelectedItem.Text = (myReader["Department"].ToString());
                ddlGroup.SelectedItem.Text = (myReader["GroupName"].ToString());
            }
            con.Close();
        }   
    }

html标记

<asp:DropDownList ID="ddlDepartment" AutoPostBack="True"  runat="server"  AppendDataBoundItems="True"  BackColor="#F3F3F3" ForeColor="#838383" 
             Height="25px" style="text-align: left"  Width="135px" DataSourceID="SqlDataSourceDepartment" DataTextField="DepartmentName" DataValueField="DepartmentID" OnDataBound="ddlDepartment_DataBound"  >
                <asp:ListItem Value="0">Select Department</asp:ListItem>
</asp:DropDownList>

<asp:DropDownList ID="ddlGroup" runat="server" BackColor="#F3F3F3"  ForeColor="#838383" Height="25px" style="text-align: left; margin-bottom: 0px;" Width="145px" DataSourceID="SqlDataSourceGroup" DataTextField="GroupName" DataValueField="GroupID" AutoPostBack="true" OnDataBound="ddlGroup_DataBound" AppendDataBoundItems="true" > 
              <asp:ListItem>Select Group</asp:ListItem>

Answer 1

选择部门和集团时，使用以下

ddlDepartment.Items.FindByValue((myReader["Department"].ToString())).Selected = true;
ddlGroup.Items.FindByValue((myReader["GroupName"].ToString())).Selected = true;