只能读取到一条数据
网上找的一些方法都行不通
读取到全部数据在添加到数组
public void load()
{
ArrayList list = new ArrayList();
openDatabase();
cmd = new SqlCommand("SELECT tagvalue_ FROM test", conn);
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
list.Add( dr.GetInt32(dr.GetOrdinal("tagvalue_")));
}