title: Set value for DictionaryEntry
body: <p>Please see my code:</p>
  
  <pre><code>IDictionary dictionary = new Hashtable();
  const string key = "key";
  const string value = "value";
  dictionary[key] = null; // set some trigger here
  
  // set value
  IDictionaryEnumerator dictionaryEnumerator = dictionary.GetEnumerator();
  while (dictionaryEnumerator.MoveNext())
  {
      DictionaryEntry entry = dictionaryEnumerator.Entry;
      if (entry.Value == null) // some business logic check; check for null value here
      {
          entry.Value = value; // set new value here
          break;
      }
  }
  
  Assert.AreEqual(value, dictionary[key]); // I have Fail here!
  </code></pre>
  
  <p>I wonder : </p>
  
  <ol>
  <li><p>What is correct approach for set new value for <strong>IDictionary</strong> when
  I do not know the corresponding key. </p></li>
  <li><p>Why my example is not working? As I understand I have set new value
      for <strong>DictionaryEntry</strong> by value (and value here is a reference) but
      it was not affected in source <strong>IDictionary</strong>. Why?</p></li>
  </ol>