title: Visual Studio error: "The debugger cannot unwind to this frame." on any exceptions
body: <p>I used to be able to edit and continue when an exception occurred in my Visual Studio 2015 C# (WPF if relevant) projects. I often get simple things like null reference exceptions, and I could just quickly fix the issue and continue.</p>
  
  <p>However, recently I've been constantly getting the following warning message:</p>
  
  <p><a href="https://i.stack.imgur.com/Dy9V8.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Dy9V8.png" alt="enter image description here"></a></p>
  
  <p>"The debugger cannot unwind to this frame."</p>
  
  <p>It notes that unwinding is nor possible in the following:</p>
  
  <ol>
  <li>Debugging was started via Just-In-Time debugging. - This isn't the case, I'm debugging by running the "Start debugging" from Visual Studio.</li>
  <li>An unwind is in progress - Not that I'm aware of, unless for some reason it's always in progress!</li>
  <li>A System.StackOverflowException or System.Threading.TreadAbortException - This happens on all exceptions, including simple ones like Null Reference</li>
  </ol>
  
  <p>My googling comes up with a few articles saying they've implemented this feature in 2006, other than that, only about 3 results come back!</p>
  
  <p>It seems to be project specific. In a clean new project:</p>
  
  <pre><code>Object o = null;
  String s = o.ToString();
  </code></pre>
  
  <p>Throws an exception, and lets me edit and continue the line before. In my existing project I cannot unwind and it throws up the dialog.</p>
  
  <p><strong>Edit:</strong> Tried it with a different computer and Visual Studio install and still have the issue.</p>
  
  <p>It seems to be an issue with Caliburn Micro.</p>
  
  <p>If I have a button on my user interface linked to an event in the code behind with the above code, I can rewind and debug. However, If I use cal.message.attach and put the code in the referenced ViewModel's method, then I cannot unwind. But I'm not sure.</p>