Hey,
set AutoPostback property true of ur RBLstSeries
or replace ur code by following
<asp:UpdatePanel runat="server" ID="HoodUpdatePane" UpdateMode="Conditional">
<ContentTemplate>
<asp:RadioButtonList ID="RBLstSeries" runat="server" AutoPostBack="True"
onselectedindexchanged="RBLstSeries_SelectedIndexChanged" >
<asp:ListItem Text="ELXC" Value="ELXC" Enabled="false"></asp:ListItem>
<asp:ListItem Text="ELXC-UVi" Value="ELXC-UVi" Enabled="false"></asp:ListItem>
<asp:ListItem Text="ELX" Value="ELX" Enabled="true" Selected="True"></asp:ListItem>
<asp:ListItem Text="ELX-UVi" Value="ELX-UVi" Enabled="false"></asp:ListItem>
<asp:ListItem Text="PG" Value="PG" Enabled="false"></asp:ListItem>
<asp:ListItem Text="VH2" Value="VH2"></asp:ListItem>
</asp:RadioButtonList>
<br />
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
</ContentTemplate>
</asp:UpdatePanel>
and in aspx.cs page add following event
protected void RBLstSeries_SelectedIndexChanged(object sender, EventArgs e)
{
Label1.Text = "Post back Done";
}
hope ur problem is solved
best Luck
happy coding