gistfile1.cs

using System;
using System.Data;
using System.Data.SqlClient;
using System.Transactions;
using IsolationLevel = System.Transactions.IsolationLevel;

namespace ConsoleApplication15
{
    class Program
    {
        static void Main(string[] args)
        {
            LogTrasactionInfo(1);
            using (var scope = new TransactionScope(TransactionScopeOption.Required,new TransactionOptions() {IsolationLevel = IsolationLevel.ReadCommitted}))
            {
                var connection = new SqlConnection("Data Source=.;Initial Catalog=ServicesPortal;Integrated Security=True");

                LogTrasactionInfo(2);
                ExecuteSelect(connection);            
                LogTrasactionInfo(3);

                using (var scope1 = new TransactionScope(TransactionScopeOption.RequiresNew, new TransactionOptions() {IsolationLevel = IsolationLevel.Serializable}))
                {
                    LogTrasactionInfo(4);
                    ExecuteSelect(connection);
                    scope1.Complete();
                }

                LogTrasactionInfo(5);

                scope.Complete();

            }

            LogTrasactionInfo(6);
 

            Console.ReadLine();
        }

        private static void LogTrasactionInfo(int step)
        {
            var current = Transaction.Current;
            if (current != null) Console.WriteLine("{1} Level: {0}", current.IsolationLevel, step);
            else Console.WriteLine("{0} No Tx", step);
        }

        private static int ExecuteSelect(SqlConnection connection)
        {
            {
                if (connection.State != ConnectionState.Open ) connection.Open();
                var command = new SqlCommand("Select Count(*) From dbo.Users", connection);
                var result = (int)command.ExecuteScalar();
                return result;
            }
        }
    }
}