C# 连结access

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.OleDb;
/// <summary>
/// DB 的摘要描述
/// </summary>
public class DB
{
    OleDbConnection conn = null;
    OleDbCommand cmd = new OleDbCommand();
 public DB()
 {
  //
  // TODO: 在此加入建構函式的程式碼
  //
        string dbname = System.Web.HttpContext.Current.Server.MapPath("DB_App/netData.aspx");
        string conStr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+dbname;
        conn = new OleDbConnection(conStr);
 }
    public OleDbConnection getConn()
    {
        if (conn.State == ConnectionState.Closed)
            conn.Open();
        return conn;
    }
    public void clear()
    {
        if(conn.State==ConnectionState.Open)
            conn.Close();
    }
    public string getScalar(string strSql)
    {
        cmd.Connection = getConn();
        cmd.CommandText = strSql;
        string result = cmd.ExecuteScalar().ToString();
        clear();
        return result;
    }
    public int getReturnNum(string strSql)
 &nb