title: How to use TreeView.Tag = object?
body: <p>Something like this:</p>
  
  <pre><code>Dictionary&lt;int, string&gt; myData = new Dictionary&lt;int, string&gt;();
  myData.Add(1, "England");
  myData.Add(2, "Canada");
  myData.Add(3, "Australia");
  myTreeView.Node[0].Tag = myData;
  </code></pre>
  
  <p>Then I want to get this object, how should I do it ?
  Like:</p>
  
  <pre><code>string str = new string();
  str = myTreeView.Node[0].Tag[2]; // "str" should be equal to "Canada"
  myTreeView.Node[0].Tag[1] = "Spain";
  str = myTreeView.Node[0].Tag[1]; // now "str" is equal to "Spain"
  </code></pre>
  
  <p>Second question - what will return this expression:</p>
  
  <pre><code>Dictionary&lt;int, string&gt; myData = new Dictionary&lt;int, string&gt;();
  myData.Add(1, "England");
  myData.Add(2, "Canada");
  myData.Add(3, "Australia");
  
  string str1 = new string();
  str = myData[4]; // there isn't such a key as 4
  </code></pre>
  
  <p>Exception or null ?</p>