title: C# An item with the same key has already been added
body: <p>Even though I'm checking whether the map already contains the key just before I add it, I receive this error..</p>
  
  <pre><code>if (ShortBuffer.ContainsKey(GetTuple(data))) return;
  ShortBuffer.Add(GetTuple(data),                 &lt;----- ERROR OCCURS HERE
      new Tuple&lt;Timer, int, bool, Data&gt;(
          new Timer(Convert.ToInt32(Ini.ReadValue("intervals", "clientbuffershort"))), 0, false, data));
  </code></pre>
  
  <p>The GetTuple method:</p>
  
  <pre><code>private static Tuple&lt;string, string, string&gt; GetTuple(Data data)
  {
      return new Tuple&lt;string, string, string&gt;(data.AucxisErrorId, data.ClientId, data.Area);
  }
  </code></pre>
  
  <p>Any thoughts? Thanks!</p>