Get TransactionScope to work with async / await

Question

I'm trying to integrate async/await into our service bus. I implemented a SingleThreadSynchronizationContext based on this example http://blogs.msdn.com/b/pfxteam/archive/2012/01/20/10259049.aspx.

And it works fine, except for one thing: TransactionScope. I await for stuff inside the TransactionScope and it break the TransactionScope.

TransactionScope doesn't seems to play nice with the async/await, certainly because it store things in the thread using ThreadStaticAttribute. I get this exception :

"TransactionScope nested incorrectly.".

I tried to save TransactionScope data before queuing the task and restore it before running it but it doesn't seems to change a thing. And TransactionScope code is a mess, so it's really hard to understand what's going on there.

Is there a way to make it work ? Is there some alternative to TransactionScope?

Answer 1

In .NET Framework 4.5.1, there is a set of new constructors for TransactionScope that take a TransactionScopeAsyncFlowOption parameter.

According to the MSDN, it enables transaction flow across thread continuations.

My understanding is that it is meant to allow you to write code like this:

// transaction scope
using (var scope = new TransactionScope(... ,
  TransactionScopeAsyncFlowOption.Enabled))
{
  // connection
  using (var connection = new SqlConnection(_connectionString))
  {
    // open connection asynchronously
    await connection.OpenAsync();

    using (var command = connection.CreateCommand())
    {
      command.CommandText = ...;

      // run command asynchronously
      using (var dataReader = await command.ExecuteReaderAsync())
      {
        while (dataReader.Read())
        {
          ...
        }
      }
    }
  }
  scope.Complete();
}

Answer 2

Bit late for an answer but I was having the same issue with MVC4 and I updated my project from 4.5 to 4.5.1 by right clicking on project go to properties. Select application tab change target framework to 4.5.1 and use transaction as follow.

using (AccountServiceClient client = new AccountServiceClient())
using (TransactionScope scope = new TransactionScope(TransactionScopeAsyncFlowOption.Enabled))
{
}

Answer 3

You can use DependentTransaction created by Transaction.DependentClone() method:

static void Main(string[] args)
{
  // ...

  for (int i = 0; i < 10; i++)
  {

    var dtx = Transaction.Current.DependentClone(
        DependentCloneOption.BlockCommitUntilComplete);

    tasks[i] = TestStuff(dtx);
  }

  //...
}


static async Task TestStuff(DependentTransaction dtx)
{
    using (var ts = new TransactionScope(dtx))
    {
        // do transactional stuff

        ts.Complete();
    }
    dtx.Complete();
}

Managing Concurrency with DependentTransaction

http://adamprescott.net/2012/10/04/transactionscope-in-multi-threaded-applications/