Non uso eventi server:
pagina aspx
codice:
<%@ Page Language="vb" AutoEventWireup="false" Codebehind="a.aspx.vb" Inherits="corso_apogeo.a"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
	<HEAD>
		<title>a</title>
		<meta content="Microsoft Visual Studio .NET 7.1" name="GENERATOR">
		<meta content="Visual Basic .NET 7.1" name="CODE_LANGUAGE">
		<meta content="JavaScript" name="vs_defaultClientScript">
		<meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">
		<script language="javascript">
<!--
function r_ab_click()
{
	if(document.getElementById("RadioButtonA").checked)
	{
		document.getElementById("CheckBoxListA").style.visibility = "hidden";
		document.getElementById("CheckBoxListB").style.visibility = "visible";
	}
	else
	{
		document.getElementById("CheckBoxListA").style.visibility = "visible";
		document.getElementById("CheckBoxListB").style.visibility = "hidden";
	}
	
}
//-->
		</script>
	</HEAD>
	<body MS_POSITIONING="FlowLayout">
		<form id="Form1" method="post" runat="server">
			

<asp:button id="Button1" runat="server" Text="Button"></asp:button></P>
			

<asp:radiobutton id="RadioButtonA" runat="server" Text="Radio A" GroupName="radio_a_b"></asp:radiobutton><asp:radiobutton id="RadioButtonB" runat="server" Text="Radio B" GroupName="radio_a_b"></asp:radiobutton></P>
			

<INPUT id="r_a" onclick="r_ab_click();" type="radio" value="a" name="r_ab"><INPUT id="r_b" onclick="r_ab_click();" type="radio" value="b" name="r_ab">
			</p>
			


				<table>
					<tr>
						<td><asp:checkboxlist id="CheckBoxListA" runat="server"></asp:checkboxlist></td>
						<td><asp:checkboxlist id="CheckBoxListB" runat="server"></asp:checkboxlist></td>
					</tr>
				</table>
			</P>
		</form>
	</body>
</HTML>

codice sottostante:
codice:
    Private Sub RadioButtonA_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles RadioButtonA.Init
        Dim r As System.Web.UI.WebControls.RadioButton = DirectCast(sender, System.Web.UI.WebControls.RadioButton)
        r.Attributes.Add("onclick", "r_ab_click();")


    End Sub

    Private Sub RadioButtonB_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles RadioButtonB.Init
        Dim r As System.Web.UI.WebControls.RadioButton = DirectCast(sender, System.Web.UI.WebControls.RadioButton)
        r.Attributes.Add("onclick", "r_ab_click();")
    End Sub


Ti ho fatto vedere come ti conviene utilizzare un <input type radio piuttosto che un <asp:radiobutton

se vuoi, e forse è meglio, metti per esempio

<div id="divA"><asp:checkboxlist /></div>

e renti visibile/invisibile divA e divB

l' <asp:button l'ho messo solo per collaudo, nel contesto non serve

ciao