Using Transactions or SaveChanges false and AcceptAllChanges

Question

I have been investigating transactions and it appears that they take care of themselves in EF as long as I pass false to SaveChanges   and then call AcceptAllChanges   if there are no errors   SaveChanges false          AcceptAllChanges      What if something goes bad  don t I have to rollback or  as soon as my method goes out of scope  is the transaction ended   What happens to any indentiy columns that were assigned half way through the transaction  I presume if somebody else added a record after mine before mine went bad then this means there will be a missing Identity value   Is there any reason to use the standard TransactionScope class in my code

User · Accepted Answer

With the Entity Framework most of the time SaveChanges() is sufficient. This creates a transaction, or enlists in any ambient transaction, and does all the necessary work in that transaction.

Sometimes though the SaveChanges(false) + AcceptAllChanges() pairing is useful.

The most useful place for this is in situations where you want to do a distributed transaction across two different Contexts.

I.e. something like this (bad):

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();
}

If context1.SaveChanges() succeeds but context2.SaveChanges() fails the whole distributed transaction is aborted. But unfortunately the Entity Framework has already discarded the changes on context1, so you can't replay or effectively log the failure.

But if you change your code to look like this:

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();

}

While the call to SaveChanges(false) 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 ObjectStateManager if you want.

This means if the transaction actually throws an exception you can compensate, by either re-trying or logging state of each contexts ObjectStateManager somewhere.

See my blog post for more.

User · Answer

If you are using EF6  Entity Framework 6    this has changed for database calls to SQL  See  http   msdn microsoft com en-us data dn456843 aspx  use context Database BeginTransaction   From MSDN    using  var context   new BloggingContext            using  var dbContextTransaction   context Database BeginTransaction                    try                         context Database ExecuteSqlCommand                     UPDATE Blogs SET Rating   5                           WHERE Name LIKE   Entity Framework                                      var query   context Posts Where p   gt  p Blog Rating  gt   5                foreach  var post in query                                  post Title      Cool Blog                                 context SaveChanges                  dbContextTransaction Commit                        catch  Exception                          dbContextTransaction Rollback      Required according to MSDN article              throw    Not in MSDN article  but recommended so the exception still bubbles up

User · Answer

Because some database can throw an exception at dbContextTransaction Commit   so better this   using  var context   new BloggingContext          using  var dbContextTransaction   context Database BeginTransaction              try               context Database ExecuteSqlCommand               UPDATE Blogs SET Rating   5                     WHERE Name LIKE   Entity Framework                          var query   context Posts Where p   gt  p Blog Rating  gt   5          foreach  var post in query                      post Title      Cool Blog                     context SaveChanges false           dbContextTransaction Commit            context AcceptAllChanges               catch  Exception                dbContextTransaction Rollback

[c#] Using Transactions or SaveChanges(false) and AcceptAllChanges()?

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