<html>
<head>
<script language="VB" runat="server">
public Sub Page_Load(Sender As Object,e As EventArgs)
' Form the script to be registered at client side.
Dim scriptString As String = "<script language=JavaScript> function DoClick() {"
scriptString += "showMessage2.innerHTML='<h4>Welcome to Microsoft .NET!</h4>'}"
scriptString += "function Page_Load(){ showMessage1.innerHTML="
scriptString += "'<h4>RegisterStartupScript Example</h4>'}<"
scriptString += "/"
scriptString += "script>"
If(Not Me.IsStartupScriptRegistered("Startup")) Then
Me.RegisterStartupScript("Startup", scriptString)
End If
End Sub
</script>
</head>
<body topmargin="20" leftmargin="10" onload="Page_Load()">
<form id="myForm" runat="server">
<span id="showMessage1"></span>
<br>
<input type="button" value="ClickMe" onclick="DoClick()">
<br>
<span id="showMessage2"></span>
</form>
</body>
</html>
MSDN上的源码,你自己分析一下吧~