我正在使用Visual Studio 2019将.Net 4.0 Framework网站转换为Web应用程序。
我已经完成了转换，但是当我构建Web应用程序时，我得到错误“名称'MessageLabel'在当前上下文中不存在”。
我的代码如下-
Offline.aspx:

<%@ Page Language="C#" MasterPageFile="~/MasterPageUnsecure.master" AutoEventWireup="true" CodeFile="Offline.aspx.cs" Inherits="Offline" %>

<asp:Content ContentPlaceHolderID="Main" runat="server">

    
        <div style=" margin-left:15px;">
        
            <asp:Label ID="Label1" runat="server" Text="This feature is offline" CssClass="pageHeader"></asp:Label><br />
            <br />
            <asp:Label ID="MessageLabel" runat="server" Text="Label">
                </asp:Label>
        </div>
 
</asp:Content>

代码文件：

using System;

public partial class Offline : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        MessageLabel.Text =
            "This part of the site is temporarily offline for maintenance and will be available for you to use again shortly.<br><br>"
            + "If you require further information please contact " + ApplicationLogicBLL.AdministratorsEmailAddress
            + " or call " + ApplicationLogicBLL.AdministratorsTelephoneNumber + ".";
    }
}

我一直在网上寻找试图改变CodeFile到CodeBehind，没有工作。
任何帮助将不胜感激。
谢谢
[更新]
我现在有-

using System;
    
    namespace SSIRS_Web_Application
    {
        public partial class Offline : System.Web.UI.Page
        {
            protected void Page_Load(object sender, EventArgs e)
            {
                MessageLabel.Text =
                    "This part of the site is temporarily offline for maintenance and will be available for you to use again shortly.<br><br>"
                    + "If you require further information please contact " + ApplicationLogicBLL.AdministratorsEmailAddress
                    + " or call " + ApplicationLogicBLL.AdministratorsTelephoneNumber + ".";
            }
        }
    }

还有-

<%@ Page Language="C#" MasterPageFile="~/MasterPageUnsecure.master" AutoEventWireup="true" CodeBehind="Offline.aspx.cs" Inherits="SSIRS_Web_Application.Offline" %>

<asp:Content ContentPlaceHolderID="Main" runat="server">

    
        <div style=" margin-left:15px;">
        
            <asp:Label ID="Label1" runat="server" Text="This feature is offline" CssClass="pageHeader"></asp:Label><br />
            <br />
            <asp:Label ID="MessageLabel" runat="server" Text="Label">
                </asp:Label>
        </div>
 
</asp:Content>

仍然得到同样的错误