using System;

using System.Collections.Generic;

using System.Transactions;

public class Program

{

    public static Dictionary<Guid, List<int>> testGroup = new Dictionary<Guid, List<int>>();

    public static void Main()

    {

        using (var scope = new TransactionScope())

        {

            var current = System.Transactions.Transaction.Current;

            current.TransactionCompleted += TransactionCompleted;

            testGroup.Add(current.TransactionInformation.DistributedIdentifier, null);

            Console.WriteLine(testGroup.Count);

        }

​

        Console.WriteLine(testGroup.Count);     

    }

    private static void TransactionCompleted(object sender, TransactionEventArgs e)

    {

        var transaction = sender as Transaction;

        testGroup.Remove(transaction.TransactionInformation.DistributedIdentifier);

    }

}