Data structure list that holds two items and can return one by the other
<p>I have a <code>dictionary</code> that holds <code>int</code> as a key and <code>string</code> as a value.</p>

<p>I can get <code>string</code> by giving it the <code>int</code>. What I want is a data structure that will enable me that AND the ability to get <code>int</code> by giving it the <code>string</code>.</p>

<p>So I want it to work both ways. What do I use for that?</p>

<p>Oh, and I know for a fact that every int and every string are unique.</p>