Use the following code
<asp:radiobuttonlist id="rbShowOrHide" runat="server" autopostback="True" cssclass="fontcolor" onselectedindexchanged="rbShowOrHide_SelectedIndexChanged" repeatdirection="Horizontal" width="100%" xmlns:asp="#unknown">
<asp:listitem value="hide">hide</asp:listitem>
<asp:listitem selected="True" value="show">show</asp:listitem>
</asp:radiobuttonlist>
and .cs page code is
protected void rbShowOrHide_SelectedIndexChanged(object sender, EventArgs e)
{
if (rbShowOrHide.SelectedValue == "show")
{
txtVisibleOrNon.Visible = true;
}
else
txtVisibleOrNon.Visible = false;
}
may be its help u..
Continue with your coding fun :-)