global.asax

《ASP.NET C#程序设计案例教程》

<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.OleDb" %>
<Script language="VBScript" runat="server">
	'当网站启动后，第1位客户访问时会执行该事件，首先会读取该表，如果记录集为空，就插入一条记录，并赋初值为0
	Sub Application_OnStart
		Dim conn As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Server.Mappath("temp.mdb"))	
		Dim strSql As String = "Select * From counters"
		Dim cmd As New OleDbCommand(strSql, conn)							'建立Command对象
		conn.Open
		Dim dr As OleDbDataReader = cmd.ExecuteReader()						'建立DataReader对象
		'下面判断数据库中是否已经有记录，如没有，则添加一条记录
		If dr.HasRows=False Then 
			Call InitialVisitNum()										'调用过程添加一条记录
		End If
		conn.Close
	End Sub

	'每一位客户访问该页面时,此时数据库中肯定有值，只要给访问次数加1即可
	Sub Session_OnStart
		Dim conn As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Server.Mappath("temp.mdb"))	
		Dim strSql As String = "Update counters Set VisitNum = VisitNum + 1"
		Dim cmd As New OleDbCommand(strSql, conn)							
		conn.Open
		cmd.ExecuteNonQuery()
		conn.Close
	End Sub

	'该过程用来添加一条初始记录
	Sub InitialVisitNum()
		Dim conn As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Server.Mappath("temp.mdb"))	
		Dim strSql As String = "Insert Into counters(VisitNum) Values(0)"
		Dim cmd As New OleDbCommand(strSql, conn)							
		conn.Open
		cmd.ExecuteNonQuery()
		conn.Close
	End Sub

</Script>