Show AJAX ModalPopup on GridView RowCommand in ASP.Net

Css:

<style type="text/css">
        .WhiteBG
        {
            background-color: White;
        }
        .modalpopup
        {
            background-color: #ADADAD;
            filter: Alpha(Opacity=70);
            opacity: 0.70;
            -moz-opacity: 0.70;
        }
    </style>

Register the AjaxControlToolKit in Page like this:

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>

HTML:

<cc1:ToolkitScriptManager runat="server">
        </cc1:ToolkitScriptManager>
        <asp:GridView ID="gvDemo" runat="server" OnRowCommand="GriRowDataBound" DataKeyNames="Code"
            AutoGenerateColumns="false">
            <Columns>
                <asp:BoundField DataField="Name" HeaderText="Name" />
                <asp:TemplateField HeaderText="">
                    <ItemTemplate>
                        <asp:LinkButton ID="lnkDownload" runat="server" Text="Open" CommandName="Select"
                            CommandArgument='<%# Eval("Name") %>'></asp:LinkButton>
                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>
<asp:Panel ID="pnlModalDemo" runat="server" CssClass="WhiteBG" Style="width: 455px;
            padding: 5px; min-height: 96px; display: none;">
              Your Modal Popup Message
            <br />
            <asp:Button ID="btnCancel" Text="Cancel" runat="server" />
        </asp:Panel>
        <asp:LinkButton ID="lnkFake" runat="server">
        </asp:LinkButton>
        <cc1:ModalPopupExtender ID="mpModalDemo" runat="server" PopupControlID="pnlModalDemo"
            TargetControlID="lnkFake" BackgroundCssClass="modalpopup" BehaviorID="mpModalDemo"
            CancelControlID="btnCancel">
        </cc1:ModalPopupExtender>

C#:

protected void GriRowDataBound(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "Select")
        {
            mpModalDemo.Show();          
        }
    }

Thanks..