多个LinkButton导航

界面：
    <asp:PlaceHolder ID="PlaceHolder1" runat="server">
        <asp:LinkButton ID="LinkButton1" runat="server" OnClick="LinkButton_Click">导航1</asp:LinkButton>
        <asp:LinkButton ID="LinkButton2" runat="server" OnClick="LinkButton_Click">导航2</asp:LinkButton>
        <asp:LinkButton ID="LinkButton3" runat="server" OnClick="LinkButton_Click">导航3</asp:LinkButton>
        <asp:LinkButton ID="LinkButton4" runat="server" OnClick="LinkButton_Click">导航4</asp:LinkButton>
        <asp:LinkButton ID="LinkButton5" runat="server" OnClick="LinkButton_Click">导航5</asp:LinkButton>

    </asp:PlaceHolder>
    <br />
    <asp:LinkButton ID="LinkButton6" runat="server">其他LinkButton</asp:LinkButton>

CS文件加一个事件：
        protected void LinkButton_Click(object sender, EventArgs e)
        {
            foreach (Control c in PlaceHolder1.Controls)
            {
                if (c is LinkButton)
                {
                    (c as LinkButton).Enabled = true;
                }
            }
            (sender as LinkButton).Enabled = false;
        }