protected void thanaSendMedicineDropDownList_SelectedIndexChanged(object sender, EventArgs e) { int id = int.Parse(thanaSendMedicineDropDownList.SelectedValue); centerSendMecinieDropDownList.DataSource = centerManager.CenterInThana(id); centerSendMecinieDropDownList.DataTextField = "CenterName"; centerSendMecinieDropDownList.DataValueField = "Id"; centerSendMecinieDropDownList.DataBind(); }