title: Concurrency exceptions in Entity Framework
body: <p>When calling <code>SaveChanges</code> / <code>SaveChangesAsync</code> in Entity Framework (CF, C#), if a change conflict occurs (for example, the values has been updated since last read thingy), then which of these two exceptions <code>DbUpdateConcurrencyException</code> OR <code>OptimisticConcurrencyException</code> shall I catch? </p>
  
  <p>And what is the difference between them?</p>