根据列表框选择填充文本框

Question

我想用列表框和数据库表中的数据填充文本框。文本框从数据库获取数据，但它只选择表的最后一行而不更改列表框选择。

我的代码：

 private void agentList_SelectedIndexChanged(object sender, EventArgs e)
    {
       string query = "Select * From tblEmployeeDetails";
        SqlConnection cn = new SqlConnection(connString);
        SqlCommand cmd = new SqlCommand(query, cn);
        SqlDataReader reader;
        {
            try
            {
                cn.Open();

                reader = cmd.ExecuteReader();
                {
                    while (reader.Read())
                    {
                        AgentId.Clear();
                        AgentId.Text = reader.GetInt32(0).ToString();
                        FullNameTxb.Text = reader.GetString(2);
                        emailtxb.Text = reader.GetString(8);
                        winLogtxb.Text = reader.GetString(1);
                        passwordtxb.Text = reader.GetString(3);
                        dobtxb.Text = reader.GetString(6);
                        addresstxa.Text = reader.GetString(9);
                        contactNotxb.Text = reader.GetString(10);
                        niNotxb.Text = reader.GetString(11);
                        contactNotxb.Text = reader.GetString(10);
                        sortCodetxb.Text = reader.GetString(12);
                        accountNotxb.Text = reader.GetString(13);
                        startdatetxb.Text = reader.GetString(14);
                        finsishdatetxb.Text = reader.GetString(15);
                        teamcmb.Text = reader.GetString(16);
                        basicsRatetxb.Text = reader.GetDecimal(17).ToString();
                        commRatetxb.Text = reader.GetDecimal(18).ToString();
                        contracthourstxb.Text = reader.GetInt32(19).ToString();
                        mainShifttxb.Text = reader.GetString(20);
                        fridayShifttxb.Text = reader.GetString(4);
                        activecmb.Text = reader.GetBoolean(5).ToString();
                        nokNametxb.Text = reader.GetString(21);
                        nokNumtxb.Text = reader.GetString(21);
                        gendercmb.Text = reader.GetString(23);
                        empTypesmb.Text = reader.GetString(24);
                        securitycmb.Text = reader.GetString(27);
                        //mondayckb.Checked = reader.GetBoolean(26);
                        //tuedayckb.Checked = reader.GetBoolean(27);
                        //wendnesdayckb.Checked = reader.GetBoolean(28);
                        //thursdayckb.Checked = reader.GetBoolean(29);
                        //fridaydkb.Checked = reader.GetBoolean(30);
                        //saturdayckb.Checked = reader.GetBoolean(31);
                        //sundaycbk.Checked = reader.GetBoolean(32);
                        //mondayckb.Checked = reader.GetBoolean(25); 
                        //tuedayckb.Checked = reader.GetBoolean(25);
                        //basicsRatetxb.Text = reader.GetString(16);
                        //activecmb.Text = reader.GetBoolean(15).ToString();
                        //dateTimePicker1.Value = reader.GetDateTime(5);
                    }
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                cn.Close();
            }
        }
    }