not able to add asp control in sharepoint custom page

 <%@ Page language="C#" CodeBehind="CustomerCard.cs"  Inherits="Microsoft.SharePoint.Publishing.PublishingLayoutPage,Microsoft.SharePoint.Publishing,Version=15.0.0.0,Culture=neutral,PublicKeyToken=71e9bce111e9429c" MasterPageFile="../_catalogs/masterpage/v4.master"%>

<%@ Register Tagprefix="SharePointWebControls" Namespace="Microsoft.SharePoint.WebControls" Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register Tagprefix="WebPartPages" Namespace="Microsoft.SharePoint.WebPartPages" Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register Tagprefix="PublishingWebControls" Namespace="Microsoft.SharePoint.Publishing.WebControls" Assembly="Microsoft.SharePoint.Publishing, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %> 
<%@ Register Tagprefix="PublishingNavigation" Namespace="Microsoft.SharePoint.Publishing.Navigation" Assembly="Microsoft.SharePoint.Publishing, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register Tagprefix="PublishingNavigation" Namespace="Microsoft.SharePoint.Publishing.Navigation" Assembly="Microsoft.SharePoint.Publishing, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Register TagPrefix="SharePointWebControls" Namespace="Microsoft.SharePoint.WebControls"
    Assembly="Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>
<%@ Assembly Name="Microsoft.Web.CommandUI, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

<asp:Content ID="Content1" runat="server" ContentPlaceHolderID="PlaceHolderMain">
    <link rel="Stylesheet" type="text/css" href="../_layouts/15/SPTestHnG/Blue.css" />
  
    <div class="ShowTitle">
        <asp:Label ID="lblTitle" runat="server"></asp:Label></div>
        <asp:Button ID="btnDeleteCard" runat="server" Text="Delete" CssClass="buttonSmall"
        OnClientClick="return confirm('Delete Customer?');" OnClick="btnDeleteCard_Click" />
    
    
 </asp:Content>
while this aspx page deploy through share point designer..error "The event handler 'OnClick' is not allowed in this page"