下面是一段数据更新的代码，数据库应该是打开一次关一次，还是打开两次关两次？那种设计更合理一点？

<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.OleDb" %>
<%@ Page Language="C#" Debug="true" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><script runat="server">
    private void caxun_click(object sender, EventArgs e)
    {
        string sqlStr = "select * from link where sitename='" + TextBox1.Text + "'";
        //建立Connection对象
        OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=d:\wwwlink.mdb");
        //建立Command对象
        OleDbCommand cmd = new OleDbCommand(sqlStr, conn);
        //----------
        //打开数据库连接
        conn.Open();
        //建立DataReader对象
        OleDbDataReader dr = cmd.ExecuteReader();
        while(dr.Read())
        {
            TextBox2.Text = dr["sitename"].ToString();
            TextBox3.Text = dr["URL"].ToString();
            TextBox4.Text = dr["intro"].ToString();
            TextBox5.Text = dr["grade"].ToString();
        }
        conn.Close();
    }
    private void gengxin_click(object sender, EventArgs e)
    {
        //string sqlStr = "select * from link where sitename='" + TextBox1.Text + "'";
        string sqlStr = "update link set [sitename]='"+TextBox2.Text+"' , [URL]='"+TextBox3.Text+"' , [intro]='"+TextBox4.Text+"', [grade]='"+TextBox5.Text+"' where [sitename]='"+TextBox1.Text+"'";
        OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=d:\wwwlink.mdb");
        OleDbCommand cmd = new OleDbCommand(sqlStr, conn);
        conn.Open();
        OleDbDataReader dr = cmd.ExecuteReader();
        conn.Close();
        message.Text = "数据已更新！";
        TextBox2.Text = "";
        TextBox3.Text = "";
        TextBox4.Text = "";
        TextBox5.Text = "";
    }
</script><html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>无标题页</title>
</head>
<body>
    <form id="form1" runat="server">
    <div style="text-align: center">
        网站更改<br />
        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
        <asp:Button ID="Button1" runat="server" OnClick="caxun_click" Text="查询" /><br />
        <br />
        网站名称：<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox><br />
        网站地址：<asp:TextBox ID="TextBox3" runat="server"></asp:TextBox><br />
        网站简介：<asp:TextBox ID="TextBox4" runat="server"></asp:TextBox><br />
        网站评分：<asp:TextBox ID="TextBox5" runat="server"></asp:TextBox><br />
        <br />
        <asp:Button ID="Button2" runat="server" Text="更新" OnClick="gengxin_click" Height="23px" Width="45px" />
        <br />
        <asp:Label ID="message" runat="server"></asp:Label>
    </div>
    </form>
</body>
</html>