Hi,
Try this-
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<asp:panel id="Panel1" runat="server" xmlns:asp="#unknown">
<asp:checkbox id="CheckBox1" runat="server" checked="true" />
<asp:panel id="Panel2" runat="server">
<asp:checkbox id="CheckBox2" runat="server" />
<asp:checkbox id="CheckBox3" runat="server" />
</asp:panel>
</asp:panel>
</form>
</body>
</html>
protected void Page_Load(object sender, EventArgs e)
{
if (((CheckBox)Panel1.FindControl("CheckBox1")).Checked)
{
foreach (Control ctrl in ((Panel)Panel1.FindControl("Panel2")).Controls)
{
if (ctrl.GetType() == typeof(CheckBox))
{
}
}
}
}