title: Visual Studio Debugger does not break on NullReferenceException, although checkbox is set in debugging options
body: <p>I manually migrated a Visual Studio 2012 "website" to a "ASP web project" to be able to use environment-specific web.configs (using transformation).</p>
  
  <p>After migration my debugger does not stop anymore at exceptions.</p>
  
  <p>In my output view I can see that a NullReferenceException is raised, my HTTP-REST-client receives "400 bad request", but the debugger ignores that exception.</p>
  
  <p>I followed the instructions to enable exceptions ( <a href="https://stackoverflow.com/questions/4475464/how-do-i-allow-breaking-on-system-nullreferenceexception-in-vs2010">How do I allow breaking on &#39;System.NullReferenceException&#39; in VS2010?</a> ). In the dialog "debugging"=>"Exceptions..." NullReferenceExceptions are enabled and resetting all checkboxes does also not help.</p>
  
  <p>Breakpoints are working as expected.</p>
  
  <p>The compiler also has some strange behaviour: compilation will succeed even if the code contains syntax problems. (But this might be a separate issue)</p>
  
  <p>How can I reenable the debugger?</p>