title: Using HashSet in C# 2.0, compatible with 3.5
body: <p>I really want to use hashsets in my program.  Using a dictionary feels ugly.  I'll probably start using VS2008 with .Net 3.5 some day, so my ideal would be that even though I can't (or can I?) use <a href="http://msdn.microsoft.com/en-us/library/bb359438.aspx" rel="noreferrer">hashsets</a> in VS2005, when I start using .NET 3.5, I don't want to have to change much, if anything, in order to switch to using these hashsets.</p>
  
  <p>I am wondering if anyone is aware of an existing hashset implementation designed with this in mind, or a way to use the 3.5 hashset in VS2005.</p>