title: What does purple underlines mean in visual studio editor?
body: <p>I am facing some purple (or violet?) underlines in Visual Studio 2015 today, something I have never seen before.</p>
  
  <p><a href="https://i.stack.imgur.com/gUqNc.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/gUqNc.jpg" alt="purple underlines in Visual Studio Editor"></a></p>
  
  <p>I held the cursor over the text but nothing happened(It happens sometimes).
  I googled it and got nothing.</p>
  
  <p>What does it mean? How do difference types of underlines represent different kinds of warnings in VS?</p>
  
  <p><strong>Here is some hint:</strong>
  I later found myself editing the source while the program is still running. When I stop the program, the underline disappeared. So I presume it has something to do with the current state of debugging.</p>