protected void Page_Load(object sender, EventArgs e)        {            string connectionString = @"Data Source=.;Initial Catalog=Pubs;Integrated Security=SSPI";            string selectSQL = "SELECT au_lname, au_fname, au_id FROM Authors";            SqlConnection con = new SqlConnection(connectionString);            SqlCommand cmd = new SqlCommand(selectSQL, con);            SqlDataAdapter adapter = new SqlDataAdapter(cmd);            DataSet dsPubs = new DataSet();            try            {                con.Open();                adapter.Fill(dsPubs, "Authors");                cmd.CommandText = "SELECT au_id, title_id FROM TitleAuthor";                adapter.Fill(dsPubs, "TitleAuthor");                cmd.CommandText = "SELECT title_id, title FROM Titles";                adapter.Fill(dsPubs, "Titles");                //多对多关系                DataRelation Titles_TitleAuthor = new DataRelation("Titles_TitleAuthor",                    dsPubs.Tables["Titles"].Columns["title_id"],                    dsPubs.Tables["TitleAuthor"].Columns["title_id"]);                DataRelation Authors_TitleAuthor = new DataRelation("Authors_TitleAuthor",                    dsPubs.Tables["Authors"].Columns["au_id"],                    dsPubs.Tables["TitleAuthor"].Columns["au_id"]);                dsPubs.Relations.Add(Titles_TitleAuthor);                dsPubs.Relations.Add(Authors_TitleAuthor);                foreach (DataRow rowAuthor in dsPubs.Tables["Authors"].Rows)                {                    lblList.Text += "<br /><b>" + rowAuthor["au_fname"];                    lblList.Text += " " + rowAuthor["au_lname"] + "</b><br />";                    foreach (DataRow rowTitleAuthor in rowAuthor.GetChildRows(Authors_TitleAuthor))                    {                        DataRow rowTitle = rowTitleAuthor.GetParentRows(Titles_TitleAuthor)[0];                        lblList.Text += "  ";                        lblList.Text += rowTitle["title"] + "<br />";                    }                }            }            catch (Exception err)            {                lblList.Text = "Error reading list of names. ";                lblList.Text = err.Message;            }            finally            {                con.Close();            }        }