title: How do I get past 'Could not open Source file: The given path's format is not supported' error when publishing a .NET project?
body: <p>Thanks for looking.</p>
  <h1>Background</h1>
  <p>I am working on a solution in VS2012 that has been publishing (file system) to it's destination folder with no problem whatsoever for several months.</p>
  <p>The solution builds successfully and runs in localhost successfully.</p>
  <h1>Problem</h1>
  <p>Today, I attempted to publish the solution and got this error:</p>
  <p><code>Error  1   Could not open Source file: The given path's format is not supported.   0   0  API</code></p>
  <p>As you can see, the error doesn't even point to a line number.</p>
  <p>I have tried cleaning, rebuilding, deleting everything in the destination folder, closing and then restarting Visual Studio, and so on.</p>
  <p>Still, the problem remains.  Has anyone else seen this or know the cause &amp; solution?</p>
  <h1>The last few lines from the Output window:</h1>
  <pre><code>4&gt;ExcludeFilesByExtension
  4&gt;C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v11.0\Web\Microsoft.Web.Publishing.targets(1443,5): Error : Could not open Source file: The given path's format is not supported.
  4&gt;
  ========== Build: 3 succeeded, 0 failed, 1 up-to-date, 0 skipped ==========
  ========== Publish: 0 succeeded, 1 failed, 0 skipped ==========
  </code></pre>