title: c# Best class to hold a list of values to look up after
body: <p>I have a list of values that i need to check against a constant list to know wheter they are present or not (one by one).</p>
  
  <p>Im using a dictionary buy it doesnt seem logical to have the value two times (key, value)...isnt there any class specialized for this case (and faster if possible)?</p>
  
  <p>Also it would me more reasonable if it could be declared as a constant being a predefined list</p>