title: Same dictionary key for a class instances with identical fields' values
body: <ol>
  <li><p>I have this class</p>
  
  <pre><code>class Border
  {
     int top;
     int bottom;
     int left;
     int right;
  }
  </code></pre></li>
  <li><p>And I have a <code>Dictionary</code> with <code>Border</code> as a key.</p></li>
  </ol>
  
  <p>I want to have the same key for this class, if these two values are equal. How can I do it?</p>