C#

I have a multiproject  c# solution which builds in VS2013 on my local machine. When
I do TFS MSBuild in fires the following error:

It's a just a _default. aspx page
<i>The type or namespace name 'Class1' could not be found (are you missing a using directive or an assembly reference?)</i>

What surprises me is that it has no external references and it's calling a class in the same namespace but in another file.

default.apx:

<i><%@ Page Language="C#" AutoEventWireup="true" CodeFile="default.aspx.cs" Inherits="MyProject.Service.Proxy._default"   %>
</i>

default.aspx.cs:
namespace MyProject.Service.Proxy
{

  public partial class _default : System.Web.UI.Page
    {
     protected void Page_Load(object sender, EventArgs e)
        {
            var a = new Class1();
            ......
        }
    }
}

class1.cs:
<i>namespace MyProject.Service.Proxy
{
    public class Class1
    {
        public int Number { get; set; }

        public Class1()
        {
            Number = 1;

        }
    }
}
</i>

As you can see all classes and files are in the very same namespace.


But if I write the Class1 code in default.aspx.cs IT WORKS!

<i>namespace MyProject.Service.Proxy
{
   public class Class1
   {
      public int Number { get; set; }

      public Class1()
      {
          Number = 1;
      }
  }

  public partial class _default : System.Web.UI.Page
    {
     protected void Page_Load(object sender, EventArgs e)
        {
            var a = new Class1();
            ......
        }
    }
}
</i>
I wouldn't like to end up having a too long and unreadable default.aspx.cs
Do you have any clue what I'm doing wrong?
Thanks so much