We finally got a useful response concerning the TransactionScope Timeout problem. Someone else had a similar issue and started a new thread in the Microsoft forums: http://forums.microsoft.com/forums/ShowPost.aspx?PostID=3069149&SiteID=1. The issue has been resolved, but only as of the .NET Framework 3.5. There is a new connection string parameter named "Transaction binding". This is set to "Implicit unbind", which by default causes the described (mis-)behavior. Instead, you must set it to "explicit unbind", so that queries issued after the transaction times out are still considered to be INSIDE the transaction and not in auto-commit mode. You can read the details in the forum post.

Alas, this only solves the problem when using the SqlClient ADO.NET provider. For all other transactive repositories, the issue still exists.

For the time being, I have built myself a helper class, that tries to fix the "timeout-bug" when using TransactionScope. And since I'm such a nice guy, I decided to let everyone have it ;-)

So here goes, completely commented including a usage example:

using System;
using System.Threading;
using System.Transactions;

namespace Succell.Framework.Utils
{
    /// <summary>
    /// This class is used to abort transactions when the timeout occurs.
    /// </summary>
    /// <remarks>
    /// <para>This class is required, because TransactionScopes do not abort processing, when they expire. Instead
    /// all actions done after the timeout occurs are not included in the transaction, but instead carried out
    /// normally. This can lead to inconsistencies in your data, when processing large amounts.</para>
    ///
    /// <para>This class can be used nestedly, i.e. methods called in the supplied working delegate can safely
    /// create instances of this class.</para>
    /// </remarks>
    /// <example><code>
    /// try
    /// {
    ///     using (TransactionScope ts = new TransactionScope(TransactionScopeOption.Required, new TimeSpan(0, 0, 2)))
    ///     {
    ///         new TransactionHelper(ts, delegate() {
    ///                 // do transactive work here
    ///             });
    ///         ts.Complete();
    ///     }
    /// }
    /// catch (TransactionAbortedException tae)
    /// {
    ///     // handle aborted transaction
    /// }
    /// </code>
    /// </example>
    public sealed class TransactionHelper
    {
        /// <summary>
        /// A tagging object to determine, whether the thread is aborted due to a transaction timeout
        /// </summary>
        private object _abortObject;

        /// <summary>
        /// The current thread executing the transactive work
        /// </summary>
        private Thread _currentThread;

        /// <summary>
        /// Creates a new TransactionHelper that executes transactive statements and aborts the process
        /// if a timeout occurs.
        /// </summary>
        /// <param name="toExecute">The delegate to call for processing</param>
        public TransactionHelper(ThreadStart toExecute)
        {
            if (null == toExecute)
                throw new ArgumentNullException("toExecute");

            // get current transaction
            Transaction tx = Transaction.Current;

            if (null == tx)
                throw new InvalidOperationException("You must create an ambient transaction before using the TransactionHelper");

            // Don't execute, if the transaction is already aborted
            if (tx.TransactionInformation.Status != TransactionStatus.Aborted)
            {
                // keep handle to current thread for aborting
                _currentThread = Thread.CurrentThread;

                // register completion handler
                tx.TransactionCompleted += new TransactionCompletedEventHandler(Current_TransactionCompleted);

                // execute transactive code
                try
                {
                    toExecute();
                }
                catch (ThreadAbortException tae)
                {
                    // was the thread aborted by our TransactionCompleted handler?
                    if (null != _abortObject && tae.ExceptionState == _abortObject)
                    {
                        Thread.ResetAbort();
                    }
                }
                // unregister completion handler (required when using multiple TxHelpers in one transaction,
                // otherwise multiple ThreadAbortExceptions are thrown on timeout)
                tx.TransactionCompleted -= new TransactionCompletedEventHandler(Current_TransactionCompleted);
            }
        }

        /// <summary>
        /// Transaction completion event handler, that checks, whether a timeout occured
        /// and, if so, causes the registered executing thread to abort
        /// </summary>
        /// <param name="sender">The originating transaction</param>
        /// <param name="e">The event args for this event</param>
        void Current_TransactionCompleted(object sender, TransactionEventArgs e)
        {
            // Is the transaction aborted (possibly due to timeout)?
            if (e.Transaction.TransactionInformation.Status == TransactionStatus.Aborted)
            {
                // Is the executing thread registered?
                if (null != _currentThread)
                {
                    // generate a new abortion tagging object
                    _abortObject = new object();

                    // abort the executing thread
                    _currentThread.Abort(_abortObject);
                }
            }
        }
    }
}

I hope, this helps some of you. Of course, I'll be updating my blog, as soon as some notice of how TransactionScope is supposed to be used reaches me. I know, that ThreadAbortExceptions aren't something to use lightly, but currently I see no other way.

Someone has finally found a dirty, yet working solution to the TransactionScope problem. You can register an event on the transaction, that fires, when the transaction finishes, which also happens on a timeout. You can then abort the main thread, to keep further commands from executing.

And this is also the dirty part: ThreadAbortExceptions are a little dangerous and can cause unexpected behavior. But for now it works for me, and as long as Microsoft does not come up with a better solution, I'll have to use this.

You can find more details here: http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=876150&SiteID=1

Happy Halloween everyone!

Today I'll tell you about some problems I've been having with the TransactionScope class. Namely, I've had timeouts running out, but the application still running the nested queries until they were finished. Amazingly, the data seemed to be in the tables, although the TimeoutException was thrown.

This has now happened to me in multiple applications. But today I read an article on the System.Transactions namespace (http://msdn.microsoft.com/msdnmag/issues/06/11/DataPoints/default.aspx).    There the author states, that you should open the database connection INSIDE the TransactionScope. This becomes logical, when you know that there is also a parameter you can add to the connection string named "auto-enlist" defaulting to true, that tells ADO.NET to look for an ambient transaction when connecting. So, if you open the database connection and then open a TransactionScope, the database does not seem to care about the ambient transaction.

I haven't tried yet, if this solves my problems. But since this is quite an important matter, I wonder why Microsoft does not point this out clearly. The TransactionScope may be a really great invention, but if you don't know how to use it, it causes damage instead of making things safer.

[Update]: This did not fix the problem. Instead, I built a test-app containing both a method, which first opens the database, then the TransactionScope, and a method doing it the other way around. Both methods have the same result. And that is VERY disappointing: The changes to the database made during the Transaction's non-timeout-ed period are rolled back, all changes AFTER the transaction times out are committed. I've written a post in the MSDN-Forum concerning Transactions Programming (http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=876150&SiteID=1). Let's see what they come up with.