未将代码放在单独的文件中如何继承页面基类

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;

/// <summary>
///BasePage 的摘要说明
/// </summary>
public class BasePage : System.Web.UI.Page
{
    public virtual int TODO(int a, int b)
    {
        return a + b;
    }
}

using System;

public partial class Test : BasePage
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Write(TODO(1, 2).ToString());
    }

    //覆盖父类 TODO 方法
    public override int TODO(int a, int b)
    {
        return a - b;
    }
}

<%@ Page Language="C#" Inherits="BasePage" %>

<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Write(TODO(1, 2).ToString());
    }

    //覆盖父类 TODO 方法
    public override int TODO(int a, int b)
    {
        return a - b;
    }
</script>