title: What's the difference between MemoryCache.Add and MemoryCache.Set?
body: <p>I read the <a href="https://msdn.microsoft.com/en-us/library/dd780623(v=vs.110).aspx">MSDN documentation</a> but didn't really understand it.</p>
  
  <p>I believe that the behavior of <code>Set</code> is "replace existing, or add" (atomically).</p>
  
  <p>Is that correct?</p>