高手解决！

错误 1 找不到类型或命名空间名称“BasePage”(是否缺少 using 指令或程序集引用?) G:\wwwroot\ClothesShop\Web\admin\main.aspx.cs 14 33 G:\wwwroot\ClothesShop\
这是我下载的一个B2C购物网站，可是再运行时出现这样的错误。BasePage是重写的Page的一个类，然后其他页面继承BasePage类。
basepage源码：：
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;namespace ClothesShop.Web
{
    public class BasePage : Page
    {
        protected override void SavePageStateToPersistenceMedium(object state)
        {
            LosFormatter formatter = new LosFormatter();
            StringWriter writer = new StringWriter();
            formatter.Serialize(writer, state);
            string viewState = writer.ToString();
            byte[] data = Convert.FromBase64String(viewState);
            byte[] compressedData = ViewStateHelper.Compress(data);
            string str = Convert.ToBase64String(compressedData);
            ClientScript.RegisterHiddenField("__MYVIEWSTATE", str);
        }        protected override object LoadPageStateFromPersistenceMedium()
        {
            string viewstate = Request.Form["__MYVIEWSTATE"];
            byte[] data = Convert.FromBase64String(viewstate);
            byte[] uncompressedData =
             ViewStateHelper.Decompress(data);
            string str = Convert.ToBase64String(uncompressedData);
            LosFormatter formatter = new LosFormatter();
            return formatter.Deserialize(str);
        } 
    }
}引用页面源码：：
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;namespace ClothesShop.Web.admin
{
    public partial class main : BasePage
    {
        ClothesShop.BLL.userinfo user = new ClothesShop.BLL.userinfo();
        protected void Page_Load(object sender, EventArgs e)
        {
            if (user.IsLogin() == true && user.getUserRole() == 2)
            {
                this.usernamelabel.Text = user.getUserName();
            }
            else
            {
                this.Response.Redirect("logins.aspx");
            }
        }
    }
}