ASP.NET 2.0 隨機讀取 Access 資料庫記錄：克服 ADO 快取機制

【導讀】因使用 ADO 存取 Access 資料庫會有快取，在隨機提取資料庫資料時，例如：sql="select top 10 Title,objectGuid from Document Order By Rnd(id)"，將得不到隨機記錄。本文給出範例可克服此缺陷，實現資料庫隨機讀取。

因使用 ADO 存取 Access 資料庫會有快取，在隨機提取資料庫資料時，例如：sql="select top 10 Title,objectGuid from Document Order By Rnd(id)"，將得不到隨機記錄。下列範例可克服此缺陷，實現資料庫隨機讀取。

C# 範例：

<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional //EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void Page_Load( object sender, EventArgs e )
{
Random rnd = new Random(unchecked((int)DateTime.Now.Ticks));
int intRandomNumber = rnd.Next();
string ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;
Data Source=|DataDirectory|aspxWeb.mdb;Persist Security Info=True";
string sql = "select top 10 Title,objectGuid from Document Order By Rnd(" + (-1 * intRandomNumber) + "*id)";
System.Data.OleDb.OleDbConnection cn = new System.Data.OleDb.OleDbConnection(ConnectionString);
cn.Open();
System.Data.OleDb.OleDbCommand cmd = new System.Data.OleDb.OleDbCommand(sql, cn);
System.Data.OleDb.OleDbDataReader dr = cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
GridView1.DataSource = dr;
GridView1.DataBind();
dr.Close();
cmd.Dispose();
cn.Dispose();
cn = null;
}
</script>
<html xmlns="https://www.w3.org/1999/xhtml">
<head runat="server">
<title>隨機讀取Access資料庫記錄</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false">
<Columns>
<asp:HyperLinkField DataNavigateUrlFields="objectGuid" HeaderText="文章" DataTextField="Title" DataNavigateUrlFormatString="https://dotnet.aspx.cc/article/{0}/read.aspx" />
</Columns>
</asp:GridView>
</div>
</form>
</body>
</html>