title: System.Diagnostics Debug Class Missing?
body: <p>I'm trying to write some debug output to the output window using System.Diagnostics.Debug.WriteLine().  AFAIK, the only requirement to be able to use the System.Diagnostics class is to add the System namespace (which is there by default).  I have one project where I can use the Debug class, as shown below:</p>
  
  <p><img src="https://i.stack.imgur.com/AGMly.png" alt="With Debug"></p>
  
  <p>But my current project doesn't show the debug class and I'm confused:</p>
  
  <p><img src="https://i.stack.imgur.com/Fmywf.png" alt="Debug Missing"></p>
  
  <p>Suggestions?</p>
  
  <p>EDIT:  This was the problem - I initially added my external class file as a 'Solution Item' and it placed it to the top of the solution in a folder.  When the program didn't compile because my reference on Form1 to the namespace failed, I simply dragged the class file from the solution folder to the program folder (for lack of a better description).  It was this duplication and versioning mismatch that was my problem.  As soon as I removed the reference to the 'Solution Item', my breakpoints were working again and the System.Diagnostics.Debug class was available in my class file.</p>
  
  <p><img src="https://i.stack.imgur.com/R6dWv.png" alt="Debug Class Issue Fixed"></p>