ASP.NET 2.0中随机读取Access数据库记录

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由于使用ADO访问Access数据库会有缓存，这在随机提取数据库数据时，例如：sql="select top 10 Title,objectGuid from Document Order By Rnd(id)"，将得不到随机记录，下面的例子可以克服这一缺陷，实现数据库的随机读取。

C#：

<%@ Page Language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://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="http://www.w3.org/1999/xhtml">
<head runat="server">
  <title>随机读取Access数据库记录</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="http://dotnet.aspx.cc/article/{0}/read.aspx" />
        </Columns>
      </asp:GridView>
    </div>
  </form>
</body>
</html>

VB.NET：

<%@ Page Language="VB" 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">

  Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
    Dim TimeString As String = DateTime.Now.Ticks.ToString()
    Dim a As UInt32 = UInt32.Parse(TimeString.Substring(TimeString.Length - 8, 8))
    Dim b As Int32 = BitConverter.ToInt32(BitConverter.GetBytes(a), 0)
    Dim rnd As Random = New Random(b)
    Dim intRandomNumber As Integer = rnd.Next
    Response.Write(intRandomNumber)
    Dim ConnectionString As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|aspxWeb.mdb;Persist Security Info=True"
    Dim sql As String = "select top 10 Title,objectGuid from Document Order By Rnd(" + (-1 * intRandomNumber).ToString() + "*id)"
    Dim cn As System.Data.OleDb.OleDbConnection = New System.Data.OleDb.OleDbConnection(ConnectionString)
    cn.Open()
    Dim cmd As System.Data.OleDb.OleDbCommand = New System.Data.OleDb.OleDbCommand(sql, cn)
    Dim dr As System.Data.OleDb.OleDbDataReader = cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection)
    GridView1.DataSource = dr
    GridView1.DataBind()
    dr.Close()
    cmd.Dispose()
    cn.Dispose()
    cn = Nothing
  End Sub
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
  <title>随机读取Access数据库记录</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="http://dotnet.aspx.cc/article/{0}/read.aspx" />
        </Columns>
      </asp:GridView>
    </div>
  </form>
</body>
</html>