title: Missing a using directive or an assembly reference error upon deploying the website
body: <p>I have a website, where the *.cs file lies in the App_Code folder (while adding a class item in my project, VS2010 suggested me to create this folder). I have a default.aspx.cs file which  makes use of this class. It runs without any error when I run on VS2010. </p>
  
  <p>However, when I deployed the website on the webserver via a private hosting company. It gives me this error: </p>
  
  <pre><code>Compilation Error
  
  Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. 
  
  Compiler Error Message: CS0246: The type or namespace name 'SMSAPP' could not be found (are you missing a using directive or an assembly reference?)
  </code></pre>
  
  <p>And its pointing to the line of code where I am instantiating the object of the class: </p>
  
  <pre><code>Line 84:         SMSAPP obj = new SMSAPP();
  </code></pre>
  
  <p>What exactly went wrong from the local version to the hosted version? Please help. Thanks. </p>
  
  <p>What I learned:</p>
  
  <p>Okay, so I haven't been able to run my project yet. But I learned few things which I would like to share- web applications and web sites are totally different things. Mine was a website, that's why the *.cs code's property did not have option to "Build Action" = "Compile". I converted my project from website to web application, and I could see the options being suggested in the answers here. However, no luck in the deployment. </p>