title: C#: How to construct a derived class from an existing base class object?
body: <p>Consider this, please:</p>
  
  <pre><code>class MyTreeNode: TreeNode{
     int x;
     public MyTreeNode(TreeNode tn)
     {
        x=1; 
        // Now what to do here with 'tn'???
     }
  </code></pre>
  
  <p>I know how to use <code>x</code>. But how should I use <code>tn</code> here to assign it to my <code>MyTreeNode</code> object?</p>