title: Create entry if one does not exist
body: <p>I'm trying to create a single instance of a model in my Db using <code>Entity Core</code>. The way I want it to work is, if the entry in the Db does not exist than make one. Instead of writing a getter method to do the work, is it possible to have <code>Entity Core</code> generate me a blank entry to work with and the save back?</p>
  
  <p>I tried using <code>FirstOrDefault</code> to no avail.</p>
  
  <p>Here is some sample code:</p>
  
  <pre><code>using (var context = new SearchTermInformationContext())
  {
      // this very first line should return me the single instance or create one if it doesnt exist.
      var searchTermInfo = context.SearchTermInformation.FirstOrDefault();
      searchTermInfo.num_search_terms += numSearchTerms;
      searchTermInfo.offset = offset;
      searchTermInfo.last_updated += (DateTime.UtcNow.Ticks / TimeSpan.TicksPerMillisecond).ToString();
      await context.SaveChangesAsync(ct);
  }
  </code></pre>