title: Error opening the .mdf file to app_data
body: <p>I am not able to add .mdf file in App_data(vs 2010 visual studio).
  If I right click on App_data and try to add existing item and select mydatabase.mdf and click OK I am getting this error:</p>
  
  <blockquote>
    <p>The file can not be opened because it is used by another process.Please close all  applications that might access this file and try again.</p>
  </blockquote>
  
  <p>But I am just running visual studio.</p>