dll classes can't access in app_code folder files
<p><img src="http://i.stack.imgur.com/cpLv9.png" alt="enter image description here">  I am working on asp.net(3.5)
  in my project there is one layer named app_code contain the business logic of the project </p>

<p>in this project I have added one reference file  named <em>Microsoft.ApplicationBlocks.Data</em></p>

<p>when I include namespace in <em>default.aspx.cs</em> file it works properly but when I work on the       business logic class file which is in *app_code* folder I show compile time error.</p>

<p>I have not find any solution<br>
  please give solution....</p>

<p>thanks in advance....</p>
