Entity framework transaction rollback not working

Ok. Would you suggest me to get rid of the global Context altogether?

Is it not right to confine the global Context for just reading operations for reporting etc., and dispose it off finally on Exit while we use another local Context object inside using() for db Insert, Update and Delete ??

Now have changed the updation code like this :

DbUpdateJob_DoWork(object sender, DoWorkEventArgs e)
{
using (MyContext dbContext = new MyContext())
{
using (DbContextTransaction mdbtrans =
dbContext.Database.BeginTransaction(IsolationLevel.Serializable))
{
try
{
--- db operations with entityA - 1 ( Insert records )
DbUpdateJob.ReportProgress(20);

--- db operations with entityB - 2 ( Insert records)
DbUpdateJob.ReportProgress(40);

--- db operations with entityC - 3 (Update records )
DbUpdateJob.ReportProgress(60);

--- db operations wiwth entityD - 4 (Insert records)
DbUpdateJob.ReportProgress(80);

dbContext.SaveChanges();
mdbtrans.Commit();
DbUpdateJob.ReportProgress(100);
}
catch(Exception ex)
{
mdbtrans.Rollback();
DbUpdateJob.ReportProgress(0);
}
}
}
}

DbUpdateJob_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
pbupdate.Value = e.ProgressPercentage;
if (e.ProgressPercentage == 0)
MessageBox.Show(e.Message);
if (e.ProgressPercentage == 100)
MessageBox.Show("Success..!!");

}

After creating a local Context the rollback is perfectly fine. Thank you once again.

Ok. Thank you.