c#sql server

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;
using AHUT_TetWebERP;
/// <summary>
/// DataBase 的摘要说明
/// </summary>
public class DataBase
{
    SqlConnection conn = null;
    SqlDataAdapter adapter = null;
    SqlCommand command = null;
    SqlDataReader reader = null;
    DataSet ds = null;
public DataBase()
{
  //
  // TODO: 在此处添加构造函数逻辑
  //
}
    /// <summary>
    /// 数据库连接
    /// </summary>
    public void connection()
    {
        conn = new SqlConnection(ConfigurationManager.ConnectionStrings["BWConnectionString"].ToString());
        conn.Open();
    }
    /// <summary>
    /// 关闭数据库连接
    /// </summary>
    public void CloseConnection()
    {
        if (conn != null)
            conn.Close();
    }
    /// <summary>
    /// 返回数据记录集DataSet
    /// <param name="sql">适配器的数据查询语句</param>
    /// </summary>
    public DataSet returnRecordset(string sql)
    {
        try
        {
            adapter = new SqlDataAdapter(sql, conn);
            ds = new DataSet();
            adapter.Fill(ds);
       &nbs