title: .NET tool for simple lookups?
body: <p>So I've found myself writing code along these lines lately.</p>
  
  <pre><code>Dictionary&lt;string, byte&gt; dict = new Dictionary&lt;string, byte&gt;();
  
  foreach(string str in arbitraryStringCollection)
  {
    if(!dict.ContainsKey(str))
    {
      ProcessString(str);
      dict[str] = 0;
    }
  }
  </code></pre>
  
  <p>The example is overly generic, but the common goal I find myself shooting for is "Have I done this one already?".</p>
  
  <p>I like using Dictionary for the fast key lookup, but since I never care about the value field, I can't help but feel it's slightly excessive, even if it's just a byte per entry.</p>
  
  <p>Is there a better .NET tool out there that accomplishes this, something with the key lookup speed of a Dictionary but without the arbitrary and unnecessary values?</p>