title: how to check if key and value already exists in hashtable
body: <pre><code>public static Hashtable ht = new Hashtable();
  
  public static DateTime LoggedOn = DateTime.Now;
  
  ht.Add(message, LoggedOn);//message contains different sting messages for my logfile
  </code></pre>
  
  <p>Now i want to check  if particular message exists and Time also.
  For example i have done</p>
  
  <pre><code>bool keyexists = ht.ContainsKey(message);
  
  bool valueexists = ht.ContainsValue(LoggedOn);
  </code></pre>
  
  <p>it will return true because i have added it to hastable now i want to check if it is added more than one time then do something ..how can i show something like that??</p>