用递归算法返回该元素id下面的所有子集id

private List<int> listAreaId = new List<int>();
/// <summary>
/// 递归获取本区域下面的所有子集
/// </summary>
/// <param name="areaId"></param>
private void GetAreaListId(int areaId)
{
string sql = string.Format(@"SELECT area_id FROM bi_area WHERE parent_id={0}", areaId);
var dt = DBUtil.DiningBaseInfo.ADO.ExecuteDataTable(sql);
if (dt != null && dt.Rows.Count > 0)
{
foreach (DataRow dr in dt.Rows)
{
listAreaId.Add(Convert.ToInt32(dr["area_id"].ToString()));
GetAreaListId(Convert.ToInt32(dr["area_id"].ToString()));
}
}
}