EF6交易回滚和并发问题

Question

Once I rollback my transaction and try again, it fails with DbUpdateConcurrencyException .

After looking at SQL profiler, I see that first time INSERT query is sent, as expected, while second time it tries to update , even though first one was rolled back?!

First query:

exec sp_executesql N'INSERT [dbo].[FiscalReceipt]([PurchaseTime], [ReceiptNumber], [Cash], [Card], [Bank])
VALUES (@0, @1, @2, @3, @4)
SELECT [FiscalReceiptID]
FROM [dbo].[FiscalReceipt]
WHERE @@ROWCOUNT > 0 AND [FiscalReceiptID] = scope_identity()',N'@0 datetime2(7),@1 int,@2 decimal(18,2),@3 decimal(18,2),@4 decimal(18,2)',@0='2016-02-08 15:05:43.9145089',@1=666,@2=1.70,@3=0,@4=0

Second query:

exec sp_executesql N'UPDATE [dbo].[FiscalReceipt]
SET [PurchaseTime] = @0, [Cash] = @1
WHERE ([FiscalReceiptID] = @2)
',N'@0 datetime2(7),@1 decimal(18,2),@2 int',@0='2016-02-08 15:12:11.8101261',@1=555.00,@2=2042

PS Shouldn't there be TM:Rollback or TM:Commit in the EventClass column in SQL Profiler table when something is commited?

C# Code:

NOTE: OutOfPaperException is intended to be ignored and transaction inside that scope is being commited on purpose. Changes should be rolled back on any other exception.

var transaction = DatabaseContext.Database.BeginTransaction();

            try
            {
                // Commented for debugging
                //IFiscalPrinter fPrinter = DeviceManager.GetFiscalPrinter();
                //var lastReceiptNumber = fPrinter.GetLastReceiptNumber();

                // false data for debugging
                var lastReceiptNumber = 666;
                Receipt.ReceiptNumber = lastReceiptNumber++;
                Receipt.PurchaseTime = DateTime.Now;

                DatabaseContext.SaveChanges();

                //fPrinter.PrintFiscalReceipt(Receipt);

                // Exception for debugging purpose
                if (Receipt.Cash < 500)
                {
                    throw new Exception();
                }

                transaction.Commit();

                Close();
            }
            catch (OutOfPaperException)
            {
                if (transaction != null)
                {
                    transaction.Commit();
                    Close();
                }

                MessageBoxService.ShowMessage("Promenite papir pre sledećeg štampanja!", "Nema više papira!", MessageButton.OK, MessageIcon.Warning);
            }
            catch (Exception ex)
            {
                // I added this but this doesn't help
                Receipt.PurchaseTime = new DateTime();
                Receipt.ReceiptNumber = 0;
                //Receipt.FiscalReceiptID = 0; <- I'm not allowed to do this

                if (transaction != null)
                {
                    transaction.Rollback();
                }

                MessageBoxService.ShowMessage(ex.Message, "Greška!", MessageButton.OK, MessageIcon.Error);
            }
            finally
            {
                if (transaction != null)
                {
                    transaction.Dispose();
                }
            }

DatabaseContext lifetime is equal to ViewModel's lifetime.

EDIT: Changing appropriate entry states to EntryState.Added results in successful operation, but it feels so dirty. Shouldn't entries remain in Added state on transaction rollback/fail?

EDIT2: After running this code:

using (MetalShopDB ctx = new MetalShopDB())
using (var transaction = ctx.Database.BeginTransaction())
{
    var receipt = new FiscalReceipt()
    {
        ReceiptNumber = 555,
        PurchaseTime = DateTime.Now,
        Cash = 100
    };

    ctx.FiscalReceipts.Add(receipt);

    Console.WriteLine("Has changes " + ctx.ChangeTracker.HasChanges());
    Console.WriteLine(ctx.Entry(receipt).State);

    ctx.SaveChanges();

    Console.WriteLine("Saved changes");

    Console.WriteLine("Has changes " + ctx.ChangeTracker.HasChanges());
    Console.WriteLine(ctx.Entry(receipt).State);

    transaction.Rollback();

    Console.WriteLine("Rolled back");

    Console.WriteLine("Has changes " + ctx.ChangeTracker.HasChanges());
    Console.WriteLine(ctx.Entry(receipt).State);
}

I get this output, which I find really strange, because one would expect context to be in sync with db, so when you rollback, context should follow up with the changes.

Has changes True
Added
Saved changes
Has changes False
Unchanged
Rolled back
Has changes False
Unchanged

Answer 1

For your EDIT2

When SaveChanges methods is called, if no error is found when saving (which is the case since you rollback after), the ObjectContext.AcceptAllChanges() methods is invoked which accept changes and populate primary keys, foreign keys and change entry state.

The rollback only rollback the transaction and not on the object context / change tracker.

It's to late at this point to call SaveChanges again since entities are already populated with database information even if you did a rollback.

Original Question

You throw an error (for debugging) after the SaveChanges has been successfully completed

if (Receipt.Cash < 500)
{
    throw new Exception();
}

So by following the previous logic, the AcceptAllChanges is already invoked.

EDIT

You can control the AcceptAllChanges by saving using the ObjectContext

var objectContext = ((IObjectContextAdapter) ctx).ObjectContext;
objectContext.SaveChanges(SaveOptions.DetectChangesBeforeSave);

transaction.Commmit();
objectContext.AcceptAllChanges();