Материал из .Net Framework эксперт
Page pre renderer event
<%@ Page Language="VB" %>
<script runat="server">
Sub Page_Load()
Label1.Text = "Page Load"
End Sub
Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
Label1.Text &= "<br />Button Click"
End Sub
Sub Page_PreRender()
Label1.Text &= "<br />Page PreRender"
End Sub
</script>
<html>
<head>
<title>Show Page Events</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Button
id="Button1"
Text="Click Here"
OnClick="Button1_Click"
Runat="server" />
<asp:Label
id="Label1"
Runat="server" />
</div>
</form>
</body>
</html>