title: Collect a distinct list of key values from a nested collection?
body: <p>This seems like it is completely straightforward, but my brain isn't working very well this morning, and I can't seem to find a good search expression for the answer.</p>
  
  <p>I have an <code>IList&lt;IDictionary&lt;string, string&gt;&gt;</code> and I want to get an <code>IList&lt;string&gt;</code> containing a distinct list of unique key names in my collection of dictionary objects.  What's a quick and elegant way to do this?  I'm sure the answer is simple, I just can't think of it.</p>