What does the Rollback method in EF Core do?

dataminers

Hi, RollBack method; Roll back whatever changes have been made to the database. Following example I didn't use Commit(), what will RollBack() do? What exactly did transaction.Rollback() do?

using (var context = new AppDbContext())
{
using (var transaction = context.Database.BeginTransaction())
{
try
{
var myObjectOne = new MyObjectOne() { Name = "Book" };
context.MyObjectOnes.Add(myObjectOne);
context.SaveChanges();

        var myVal = myObjectOne.Id \* 3.14;

        //Suppose an error occurs here

        var myObjectTwo = new MyObjectTwo() { Name = "Notebook", Price = 100, ReferenceId = myVal };
        context.MyObjectTwos.Add(myObjectTwo);
        context.SaveChanges();

        transaction.Commit();
    }
    catch (Exception ex)
    {
        transaction.Rollback();
    }
}

}

thanks... :confused:

Lost User

See ROLLBACK TRANSACTION (Transact-SQL) - SQL Server | Microsoft Learn[^].

dataminers

Thanks for the answer @Richard-MacCutchan I read the article, but I didn't get the exact answer to my question. The EF Core working structure is different. Each process is primarily tracked on the memory. Makes my question a little clearer. What is the difference in effect between the two codes below? FIRST CODE:

using (var context = new AppDbContext())
{
using (var transaction = context.Database.BeginTransaction())
{
try
{
var myObjectOne = new MyObjectOne() { Name = "Book" };
context.MyObjectOnes.Add(myObjectOne);
context.SaveChanges();

        var myVal = myObjectOne.Id \* 3.14;

        //Suppose an error occurs here

        var myObjectTwo = new MyObjectTwo() { Name = "Notebook", Price = 100, ReferenceId = myVal };
        context.MyObjectTwos.Add(myObjectTwo);
        context.SaveChanges();

        transaction.Commit();
    }
    catch (Exception ex)
    {
        transaction.Rollback();
    }
}

}

SECOND CODE:

using (var context = new AppDbContext())
{
using (var transaction = context.Database.BeginTransaction())
{
try
{
var myObjectOne = new MyObjectOne() { Name = "Book" };
context.MyObjectOnes.Add(myObjectOne);
context.SaveChanges();

        var myVal = myObjectOne.Id \* 3.14;

        //Suppose an error occurs here

        var myObjectTwo = new MyObjectTwo() { Name = "Notebook", Price = 100, ReferenceId = myVal };
        context.MyObjectTwos.Add(myObjectTwo);
        context.SaveChanges();

        transaction.Commit();
    }
    catch (Exception ex)
    {
        //Nothing
    }
}

}

Richard Deeming

Probably not much, but pay attention to the documentation:

DbTransaction.Dispose Method (System.Data.Common) | Microsoft Learn[^]:

Dispose should rollback the transaction. However, the behavior of Dispose is provider specific, and should not replace calling Rollback.

In other words, the using block should roll-back the transaction if you haven't called Commit; but different database providers might not implement that correctly, and might require you to explicitly call Rollback.

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

dataminers

Thank you for the explanation. Actually, I guessed but wasn't sure. Many thanks @RichardDeeming @Richard-MacCutchan