entity framework 6 and pessimistic concurrency

Pessimistic concurrency may be achieved, for example, by using something like this:

var options = new TransactionOptions
{
   IsolationLevel = System.Transactions.IsolationLevel.Serializable,
   Timeout = new TimeSpan(0, 0, 0, 10)
};

using(var scope = new TransactionScope(TransactionScopeOption.RequiresNew, options))
{ ... stuff here ...}

It seems that with VS2017, you must right-click TransactionScope before it will create a reference for: Microsoft Framework.NET Framework Version 4.6.1 Reference Assemblies System.Transactions.dll

One thread will succeed while the other times out after 10 seconds if two threads try to increase the same number, however. This is because, in order to save changes, both transactions must upgrade their shared locks to exclusive locks, but they are unable to do so since another transaction is already holding a shared lock on the same row. After some time passes with no successful transactions to break the deadlock, SQL Server will then recognise the deadlock. If one transaction fails, the shared lock will be released, allowing the second transaction to upgrade its shared lock to an exclusive lock and continue with execution.

The solution to this deadlocking is to inform the database with a UPDLOCK hint using something like:

private static TestEntity GetFirstEntity(Context context) {
return context.TestEntities
              .SqlQuery("SELECT TOP 1 Id, Value FROM TestEntities WITH (UPDLOCK)")
              .Single();
}

This code was taken from Ladislav Mrnka's blog, which seems to no longer be accessible. The use of optimistic locking is the second option.