ado.net工厂模式DbProviderFactories

DbProviderFactory f = DbProviderFactories.GetFactory(System.Configuration.ConfigurationManager.ConnectionStrings["ado"].ProviderName);
DbConnection conn = f.CreateConnection();
            
conn.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["ado"].ConnectionString;
conn.Open();

DbCommand cmd = f.CreateCommand();
cmd.CommandText = "select * from student";
cmd.Connection = conn;

DbDataReader re = cmd.ExecuteReader();
while (re.Read())
{
    int id = (int)re["StuId"];
    string name = (string)re["StuName"];
    int age = (int)re["StuAge"];

    ListViewItem item = new ListViewItem();
    item.Text = id.ToString();
    item.SubItems.Add(
        new ListViewItem.ListViewSubItem { Text = name }
        );
    item.SubItems.Add(
        new ListViewItem.ListViewSubItem { Text = age.ToString() }
        );
    listView1.Items.Add(item);
}

re.Close();
conn.Close();