The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.01 - entity-framework

Question

This is function that takes two List<int> and update corresponding tables at database. When I run both functions using threads T1 and T2 , then it shows me exception at the second foreach loop:
"The ObjectContext instance has been disposed and can no longer be
used"
I already used query like
var res = ctx.EmailDBs.Include(x => x.EmailDBid == id);
but it's not working.
Please share something to persist the ctx connection until both methods are executed.
public static void UpdateEmail(List<int> invalidEmailToUpdate, List<int> validEmailToUpdate)
{
using (OnliveMTAEntities ctx = new OnliveMTAEntities())
{
Thread T1, T2;
T1 = new Thread(() =>
{
foreach (int id in invalidEmailToUpdate)
{
var res = ctx.EmailDBs.FirstOrDefault(x => x.EmailDBid == id);
res.Status = 6;
}
});
T1.Start();
Thread.Sleep(100);
T2 = new Thread(() =>
{
foreach (int id in validEmailToUpdate)
{
var res = ctx.EmailDBs.FirstOrDefault(x => x.EmailDBid == id);
res.Status = 7;
}
});
T2.Start();
ctx.SaveChanges();
}
}

Answer 1

You need to wait until both threads T1 and T2 are fully completed. Only then you can save dataContext ctx.SaveChanges();
For that purpose is method called Join() (MSDN). Use it like that:
// previous code here
T2.Start();
// wait for threads to be done
T1.Join();
T2.Join();
// now both of them are done
ctx.SaveChanges();
// end of using(...) and other code
EDIT: I forgot to mention: using both Join(), you can get rid of Thread.Sleep(100);. I believe that this is the reason why you got error on second thread. That call will pause execution of current thread (which will start T2) for 100ms and during that time T1 succeded to complete it's work.