How to perform a transaction with an Entity Framework object context?

问题

I created very a simple database using Entity Framework 4. I'd like to be able to use transactions on entities, but I can't seem to keep changes from rolling back. I really just need a way to abandon temporary changes to entities before they are saved to the database.

For example, the following code uses an entity framework object context "MusicContainer". Inside a TransactionScope, an Artist entity is created. The transaction then ends without being completed; so I'd expect the transaction to be rolled back. But, the program runs as if I'd never created the TransactionScope in the first place; after the TransactionScope ends, the line music.SaveChanges() saves the object to the database.

class Program
{
    static void Main(string[] args)
    {
        using (MusicContainer music = new MusicContainer())
        {
            using (TransactionScope transaction = new TransactionScope())
            {
                Artist artist = new Artist { Name = "Test" };
                music.Artists.AddObject(artist);
            }
            // The transaction ended without Complete(); shouldn't the changes be abandoned?
            music.SaveChanges();
        }
    }
}

If entity framework doesn't use TransactionScope the way I'm expecting it to here, how can I get the functionality I'm looking for? I have several circumstances where the caller of a function passes in the MusicContainer, and I need to leave the MusicContainer in a clean state before I return from the function (i.e. rolling back changes so they don't accidently get saved in with another SaveChanges called on the same MusicContainer object).

回答1:

You don't need a TransactionScope at all in this scenario, SaveChanges() is all that's needed - if you have another using block with MusicContainer, this will be in a separate transaction and won't save any changes within your current using block. TransactionScope is only needed for transactions spanning multiple DB contexts.

In general a context should only be used for a unit of work consisting of related operations, once they are completed call SaveChanges(). Open a new context for each separate, unrelated unit of work. Having said that, just use this in your scenario:

        using (MusicContainer music = new MusicContainer())
        {
                Artist artist = new Artist { Name = "Test" };
                music.Artists.AddObject(artist);
                music.SaveChanges();
        }

回答2:

You have your SaveChanges in the wrong place.

class Program
{
    static void Main(string[] args)
    {
        using (MusicContainer music = new MusicContainer())
        {
            using (TransactionScope transaction = new TransactionScope())
            {
                Artist artist = new Artist { Name = "Test" };
                music.Artists.AddObject(artist);
                music.SaveChanges();
            }
            // The transaction ended without Complete(); the changes are abandoned?
        }
    }
}

You shouldn't reuse your MusicContainer if the transaction fails. Create a new one for each Unit of Work

回答3:

Entity framework should be able to use TransactionScope. You need to start a New TransactionScope if you need to rollback the changes apllied only by this method.

 using (MusicContainer music = new MusicContainer())
   {
     using (TransactionScope transaction = new TransactionScope(TransactionScopeOptions.RequiresNew))
          {
              Artist artist = new Artist { Name = "Test" };
              music.Artists.AddObject(artist);
              music.SaveChanges();
              scope.Complete(); 
          }
    }

来源：https://stackoverflow.com/questions/5222734/how-to-perform-a-transaction-with-an-entity-framework-object-context

标签

entity-framework

transactionscope