编译器错误消息: ASPNET: 请确保此代码文件中定义的类与“inherits”特性匹配，并且该类扩展的基类(例如 Page 或 UserControl)是正

asp.net(C#)投票模块报错，求大佬指导
代码如下：
Manager.aspx<%@ Page Title="" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile="Manager.aspx.cs" Inherits="Manager" %><asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    <asp:GridView ID="gvVotes" runat="server" AutoGenerateColumns="False" 
        onrowdeleting="gvVotes_RowDeleting" DataKeyNames="VoteID" 
        DataSourceID="SqlDataSource1" 
        onselectedindexchanged="gvVotes_SelectedIndexChanged" >
      <Columns>
        <asp:BoundField DataField="VoteID" HeaderText="ID" />
        <asp:BoundField DataField="VoteTitle" HeaderText="标题" />
        <asp:BoundField DataField="VoteSum" HeaderText="总投票数" />
        <asp:CheckBoxField DataField="Show" HeaderText="开放" Text="开放" />
        <asp:HyperLinkField DataNavigateUrlFields="VoteID" DataNavigateUrlFormatString="VoteEdit.aspx?voteid={0}" Text="编辑" />
        <asp:CommandField ShowDeleteButton="true" />
      </Columns>
    </asp:GridView>
</asp:Content>
Manager.aspx.csusing System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Linq.Expressions;public partial class Manager : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {    }    private BookDemo_VoteDataContext ctx = new BookDemo_VoteDataContext();//创建DataContext实例
    ///<summary>
    ///将数据绑定到gvVotes控件上
    ///</summary>    private void DataBindToGvVotes()
    {
        gvVotes.DataSource = ctx.VoteMaster.OrderByDescending(v => v.VoteID);//数据源
        gvVotes.DataKeyNames = new string[] { "VoteID" };//主键名称
        gvVotes.DataBind();//执行绑定
    }}
Site.master<%@ Master Language="C#" AutoEventWireup="true" CodeFile="Site.master.cs" Inherits="BookDemo.Vote.Site" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <asp:ContentPlaceHolder id="head" runat="server">
    </asp:ContentPlaceHolder>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:ContentPlaceHolder id="ContentPlaceHolder1" runat="server">
        
        </asp:ContentPlaceHolder>
    </div>
    </form>
</body>
</html>Site.master.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;public partial class Site : System.Web.UI.MasterPage
{
    protected void Page_Load(object sender, EventArgs e)
    {    }
}