protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
List <MDSearch> list = mss.GetAllCity(DropDownList1.SelectedValue);
DataTable dt = ListToDataTable(list);
DropDownList2.Items.Clear();
DropDownList2.Items.Add(new ListItem("请选择城市"));
foreach (DataRow dr in dt.Rows)
{
DropDownList2.Items.Add(new ListItem(dr["City"].ToString()));
}
DropDownList2_SelectedIndexChanged(null, null);
}