title: Create a file only if doesn't exists
body: <p>I want to create a file ONLY if it doesn't already exists.<br>
  A code like:</p>
  
  <pre><code>if (!File.Exists(fileName))
  {
      fileStream fs = File.Create(fileName);
  }
  </code></pre>
  
  <p>Leave it open for a race-condition in case the file will be created between the "if" to the "create".  </p>
  
  <p>How can I avoid it?</p>
  
  <p>EDIT:<br>
  <em>locks</em> can't be used here because it's a different processes (multiple instances of the same application).</p>