Weird Error on Visual Studio - "you can use the navigation bar to switch context"

Question

I am trying to link a web form to be able to access a variable on the main page. I did it until it worked. But now, when I do this, I get an error message.

Code in Site.Master

<%@ Master Language="C#" AutoEventWireup="true" CodeFile="Site.master.cs" Inherits="Site" %>

Code in Site.Master.cs

public partial class Site : System.Web.UI.MasterPage
{
    public string hi = "";

    protected void Page_Load(object sender, EventArgs e)
    {

    }
}

Code in WebForm1.aspx:

<%@ Page Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile="WebForm1.aspx.cs" Inherits="WebForm1" %>
<%@ MasterType VirtualPath="~/Site.master" %>

Code in WebForm1.aspx.cs

public partial class WebForm1 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
     {
         Master.hi="new"
     }
}

When I hang over hi, I get this message

Error in Visual Studio - "You can use the navigation bar to switch contexts

Here is another image Screenshot

If you guys could help me, it really will be great

Answer 1

MVC, WebForm-CodeFile-CodeBehind .

, , , , " " "". "", .

Answer 2

WebForm1.aspx CodeFile CodeBehind. , .