using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Transactions;

namespace ConsoleApplication14
{
    class Program
    {
        static void Main(string[] args)
        {
            var txOpt = new TransactionOptions() { IsolationLevel = IsolationLevel.ReadCommitted };
            using (var tx = new TransactionScope(TransactionScopeOption.RequiresNew, txOpt))
            {
                Method1();
                Method2();

                // Не вызовите сomplete, будет rollback на уровне ресурсов, которые участвовали в ambient транзакции
                tx.Complete();
            }
        }

        protected static void Method1()
        {
            using (var ctx = new DB1Entities())
            {
                var t1 = ctx.T1.First(o => o.ID == 1);
                t1.NAME = 3;

                // Участвует в ambient транзакции, если Enlist = true, иначе свою создаст
                ctx.SaveChanges();
            }
        }

        protected static void Method2()
        {
            using (var ctx = new DB1Entities())
            {
                var t1 = ctx.T1.First(o => o.ID == 2);
                t1.NAME = 4;

                // Работает на уровне контекста
                if (...)
                    ctx.RevertAllChanges();

                // Участвует в ambient транзакции, если Enlist = true, иначе свою создаст
                ctx.SaveChanges();
            }
        }
    }

    public static class EfHelper
    {
        public static void RevertAllChanges(this DbContext ctx)
        {
            foreach (var entry in ctx.ChangeTracker.Entries())
                entry.State = EntityState.Unchanged;
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Transactions;

namespace ConsoleApplication15
{
    public sealed class FakeTransactionalResource<T> : ISinglePhaseNotification
    {
        private T _oldObj;

        private T _obj;
        public T Obj
        {
            get { return _obj; }
            set { _obj = value; }
        }

        public FakeTransactionalResource(T obj)
            : this(obj, true)
        {
        }

        public FakeTransactionalResource(T obj, bool enlist)
        {
            _oldObj = obj;
            _obj = obj;

            if (enlist)
                Enlist();
        }

        public void Enlist()
        {
            Transaction.Current
                .EnlistVolatile(this, EnlistmentOptions.None);
        }

        #region ISinglePhaseNotification
        void ISinglePhaseNotification.SinglePhaseCommit(SinglePhaseEnlistment singlePhaseEnlistment)
        {
            Commit();

            singlePhaseEnlistment.Committed();
        }

        void IEnlistmentNotification.Commit(Enlistment enlistment)
        {
            throw new NotImplementedException();
        }

        void IEnlistmentNotification.InDoubt(Enlistment enlistment)
        {
            enlistment.Done();
        }

        void IEnlistmentNotification.Prepare(PreparingEnlistment preparingEnlistment)
        {
            preparingEnlistment.Prepared();
        }

        void IEnlistmentNotification.Rollback(Enlistment enlistment)
        {
            _obj = _oldObj;
        }

        private void Commit()
        {
            _oldObj = _obj;
        }

        #endregion
    }
}

            FakeTransactionalResource<int> ftr = null;

            var txOptions = new TransactionOptions() { IsolationLevel = IsolationLevel.ReadCommitted };
            using (var tx = new TransactionScope(TransactionScopeOption.RequiresNew, txOptions))
            {
                ftr = new FakeTransactionalResource<int>(1);

                ftr.Obj = 5;

                Console.WriteLine("Before rollback {0}", ftr.Obj);
                //tx.Complete();
            }

            Console.WriteLine("After rollback {0}", ftr.Obj); // напечатает 1