protected void districtDropDownList_SelectedIndexChanged(object sender, EventArgs e) { if (districtDropDownList.SelectedValue != "-1") { int districtId = Convert.ToInt32(districtDropDownList.SelectedValue); upazilaDropDownList.DataSource = _dropDownManager.GetAllUpazila(districtId); upazilaDropDownList.DataTextField = "UpazilaName"; upazilaDropDownList.DataValueField = "Id"; upazilaDropDownList.DataBind(); ListItem upazilaItem = new ListItem("Select Upazila", "-1"); upazilaDropDownList.Items.Insert(0, upazilaItem); } }