asp.net 完全入门 光盘内容

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
/// <summary>
/// DBConnection 的摘要说明
/// </summary>
public class DBConnection
{
private static string connectionStr = "server=.;uid=sa;password=sa;database=ReturnBook";
SqlConnection conn = null;
SqlCommand comm = null;
SqlDataAdapter sda = null;

public DataSet getDataSet(string sql)
{
conn = new SqlConnection(connectionStr);
sda = new SqlDataAdapter(sql,conn);
conn.Open();
DataSet ds = new DataSet();
try
{
sda.Fill(ds);

}
catch (Exception ex)