basic custom server control question

[sds814]

I'm using VS2012. I'm trying to follow an exercise from a book.

Here is the code for my custom server control:

namespace ServerControl
{
    [ToolboxData("<{0}:menucustomcontrol runat=\"server\"></{0}:menucustomcontrol>")]
    public class MenuCustomControl : Control
    {
        protected override void Render(HtmlTextWriter writer)
        {
            base.Render(writer);

            writer.WriteLine("<div>");
            RenderMenuItem(writer, "Apress", "[URL unfurl="true"]http://www.apress.com");[/URL]
            writer.Write(" | ");
            RenderMenuItem(writer, "Microsoft", "[URL unfurl="true"]http://www.microsoft.com");[/URL]
            writer.Write(" | ");
            RenderMenuItem(writer, "MSDN", "[URL unfurl="true"]http://msdn.microsoft.com");[/URL]
            writer.Write(" | ");
            RenderMenuItem(writer, "ASP.NET", "[URL unfurl="true"]http://asp.net");[/URL]
            writer.Write("</div>");
        }

        private void RenderMenuItem(HtmlTextWriter writer, string title, string url)
        {
            writer.Write("<span><a href=\"");
            writer.Write(url);
            writer.Write("\">");
            writer.Write(title);
            writer.WriteLine("</a><span>");
        }
    }
}

I've added the reference to ServerControl.dll in the web application project. After adding ServerControl to the toolbox and dragging the control to the aspx page, the code looks like:

<%@ Page Title="Simple User Control Demo" Language="C#" MasterPageFile="~/SimpleUserControl.Master" AutoEventWireup="true" CodeBehind="SimpleUserControl.aspx.cs" 
    Inherits="SimpleUserControl.SimpleUserControl1" %>
<%@ Register TagPrefix="apress" Namespace="ServerControl" Assembly="ServerControl" %>
<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server">

</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
    <apress:MenuCustomControl ID="Menucustomcontrol1" runat="server"></apress:MenuCustomControl>
</asp:Content>

The error I get is when compiling the web application on SimpleUserControl.aspx.designer.cs:

The type or namespace name 'ServerControl' could not be found in the global namespace (are you missing an assembly reference?)

I'm not sure what I'm doing wrong.