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copied!<p>With the Entity Framework most of the time <code>SaveChanges()</code> is sufficient. This creates a transaction, or enlists in any ambient transaction, and does all the necessary work in that transaction.</p> <p>Sometimes though the <code>SaveChanges(false) + AcceptAllChanges()</code> pairing is useful.</p> <p>The most useful place for this is in situations where you want to do a distributed transaction across two different Contexts.</p> <p>I.e. something like this (bad):</p> <pre><code>using (TransactionScope scope = new TransactionScope()) { //Do something with context1 //Do something with context2 //Save and discard changes context1.SaveChanges(); //Save and discard changes context2.SaveChanges(); //if we get here things are looking good. scope.Complete(); } </code></pre> <p>If <code>context1.SaveChanges()</code> succeeds but <code>context2.SaveChanges()</code> fails the whole distributed transaction is aborted. But unfortunately the Entity Framework has already discarded the changes on <code>context1</code>, so you can't replay or effectively log the failure.</p> <p>But if you change your code to look like this:</p> <pre><code>using (TransactionScope scope = new TransactionScope()) { //Do something with context1 //Do something with context2 //Save Changes but don't discard yet context1.SaveChanges(false); //Save Changes but don't discard yet context2.SaveChanges(false); //if we get here things are looking good. scope.Complete(); context1.AcceptAllChanges(); context2.AcceptAllChanges(); } </code></pre> <p>While the call to <code>SaveChanges(false)</code> sends the necessary commands to the database, the context itself is not changed, so you can do it again if necessary, or you can interrogate the <code>ObjectStateManager</code> if you want.</p> <p>This means if the transaction actually throws an exception you can compensate, by either re-trying or logging state of each contexts <code>ObjectStateManager</code> somewhere.</p> <p>See <a href="http://twitter.com/adjames" rel="noreferrer">my</a> <a href="http://blogs.msdn.com/alexj/archive/2009/01/11/savechanges-false.aspx" rel="noreferrer">blog post</a> for more.</p>

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