Why is TransactionScope operation is not valid?

Question

I have a routine which uses a recursive loop to insert items into a SQL Server 2005 database The first call which initiates the loop is enclosed within a transaction using TransactionScope. When I first call ProcessItem the myItem data gets inserted into the database as expected. However when ProcessItem is called from either ProcessItemLinks or ProcessItemComments I get the following error.

“The operation is not valid for the state of the transaction”

I am running this in debug with VS 2008 on Windows 7 and have the MSDTC running to enable distributed transactions. The code below isn’t my production code but is set out exactly the same. The AddItemToDatabase is a method on a class I cannot modify and uses a standard ExecuteNonQuery() which creates a connection then closes and disposes once completed.

I have looked at other posting on here and the internet and still cannot resolve this issue. Any help would be much appreciated.

using (TransactionScope processItem = new TransactionScope())
{
    foreach (Item myItem in itemsList)
    {
        ProcessItem(myItem);
    }   
    processItem.Complete();
}    
private void ProcessItem(Item myItem)
{
    AddItemToDatabase(myItem);
    ProcessItemLinks(myItem);
    ProcessItemComments(myItem);
}    
private void ProcessItemLinks(Item myItem)
{
    foreach (Item link in myItem.Links)
    {
        ProcessItem(link);
    }
}   
private void ProcessItemComments(Item myItem)
{
    foreach (Item comment in myItem.Comments)
    {
        ProcessItem(comment);
    }
}

Here is the top part of the stack trace. Unfortunately I can’t show the build up to this point as its company sensitive information which I cannot disclose.

   at System.Transactions.TransactionState.EnlistPromotableSinglePhase(InternalTransaction tx, IPromotableSinglePhaseNotification promotableSinglePhaseNotification, Transaction atomicTransaction)
   at System.Transactions.Transaction.EnlistPromotableSinglePhase(IPromotableSinglePhaseNotification promotableSinglePhaseNotification)
   at System.Data.SqlClient.SqlInternalConnection.EnlistNonNull(Transaction tx)
   at System.Data.SqlClient.SqlInternalConnection.Enlist(Transaction tx)
   at System.Data.SqlClient.SqlInternalConnectionTds.Activate(Transaction transaction)
   at System.Data.ProviderBase.DbConnectionInternal.ActivateConnection(Transaction transaction)
   at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject)
   at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
   at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
   at System.Data.SqlClient.SqlConnection.Open()

Answer 1

Distributed transactions made my hair go gray prematurely :)

Usual suspects

1. Firewall is blocking MSDTC
2. Your transaction is timing out for some reason (try increasing the timeout)
3. You have another transaction scope somewhere on the top of the code that is messing with the current transaction

Test whether MSDTC is working fine using tools like dtcping

Also test by inserting a small number of elements at first. Your code seems to be in a recursive loop which can process a large amount of data. Maybe you are running to many queries and the transaction is timing out.

Sometime System.Transactions.Transaction.Current has some clues on what happened. Add a watch against this global variable