TransactionScope in .NET 1.1

Now: Declarative Database Transactions With ServicedComponent

Developers working with Microsoft SQL Server enjoyed declarative handling of transactions since Windows NT 4.0 days. With the .NET Framework, this usually means we need to inherit a class from ServicedComponent, apply TransactionAttribute to it, and use SetAbort/SetComplete methods to notify the framework if our DB operation succeeded or failed. The framework takes care of the rest.

Simple? Yes, but…

• ServicedComponent requires you to sign your assemblies, the step considered by many developers as the unnecessary complication.
• You can’t mix transactional and non-transactional methods in one class, which forces you to split a single logical CustomerService into CustomerReader and CustomerWriter or something like that.

Future: TransactionScope in .NET 2.0

In .NET 2.0, we are going to have the TransactionScope class which solves both problems. Used as braces around a code which must run inside a database transaction and, although not the declarative style anymore, it provides a nice clean model:

using (TransactionScope scope = new TransactionScope())
{
  // open connection
  // perform database operation, which is going to run inside the transaction
    …
  // call other method and if the other method creates a TransactionScope object
  // it will share the transaction with the current method

  // All is well:
  Scope.Complete();
}

The Future's Here

OK, the code above looks as good as I’d like it to be, but Whidbey isn’t coming to production machines near me for another year or so. I had to create my own solution using .NET 1.1, and here it is. In fact, the implementation is so embarrassingly simple that I now feel ashamed I didn’t figure it out earlier!

Usage:

using (TransactionScope scope = new TransactionScope())
using (SqlConnection conn = new SqlConnection(connString))
using (SqlCommand cmd = new SqlCommand(updateSql, conn))
{
  System.Diagnostics.Debug.Assert(
         System.EnterpriseServices.ContextUtil.IsInTransaction);
    
  conn.Open();
    
  int result = cmd.ExecuteNonQuery();

  // We call it success if exactly one record was updated:
  if (result == 1)
  {
    scope.Complete();
  }
}

Here’s the complete class:

// Copyright (c) 2005 Alexander Shirshov
//
// This code is free software; you can redistribute it and/or modify it.
// However, this header must remain intact and unchanged. Additional
// information may be appended after this header. Publications based on
// this code must also include an appropriate reference.
// 
// This code is distributed in the hope that it will be useful, but 
// WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
// or FITNESS FOR A PARTICULAR PURPOSE.

using System;
using System.EnterpriseServices;

namespace Omnitalented.EnterpriseServices
{
  public class TransactionScope : IDisposable
  {
    private bool succeded;

    public TransactionScope() : this(TransactionOption.Required, 
                                TransactionIsolationLevel.Any, 60)
    {
    }

    public TransactionScope(TransactionOption transactionOption) : 
           this(transactionOption, TransactionIsolationLevel.Any, 60)
    {
    }

    public TransactionScope(TransactionOption transactionOption, 
           TransactionIsolationLevel isolationLevel, int timeoutSeconds)
    {
      ServiceConfig cfg = new ServiceConfig();
      cfg.Transaction = transactionOption;
      cfg.IsolationLevel = isolationLevel;
      cfg.TransactionTimeout = timeoutSeconds;
            
      ServiceDomain.Enter(cfg);
    }

    public void Complete()
    {
      succeded = true;
    }

    public void Dispose()
    {
      if (succeded)
      {
        ContextUtil.SetComplete();
      } 
      else
      {
        ContextUtil.SetAbort();
      }
      ServiceDomain.Leave();
    }
  }
}

Please note: The code only works in Windows 2003 Server or Windows XP; this is a requirement for the System.EnterpriseServices.ServiceDomain class.

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