title: How to implement good practise of Business Logic Layer in Real Life asp.net
body: <p>I usually create dataset as DAL, and BLL INSIDE the original project.</p>
  
  <p>After I learned Entity Framework, I know that business logic layer are commonly created in separated project(class library).</p>
  
  <p>However, ASP.NET site has no corresponding tutorial.</p>
  
  <p>For this reason, I'm quite confused when I create BLL especially during referencing.</p>
  
  <ol>
  <li>In order to complete the BLL classes, am I supposed to directly add reference like this?</li>
  </ol>
  
  <p><img src="https://i.stack.imgur.com/16JUI.jpg" alt="enter image description here"></p>
  
  <p>and then access to the entity with USING statement:</p>
  
  <p><img src="https://i.stack.imgur.com/uREeb.jpg" alt="enter image description here"></p>
  
  <p>However, the presentation layer in main project which accesses BLL might need to reference back to BLL project. I saw some of the samples putting the entire BLL project's DLL file in the main project.</p>
  
  <p>What's the correct way to reference BLL and Main project, or just reference as above?</p>
  
  <p>Are there any good tutorial I can study from?</p>