I am just going to post that, and watch what happens. I will note that this is code that I just wrote, from scratch.

public class TaxCalculator
{
    private string conStr;
    private DataSet rates;

    public TaxCalculator(string conStr)
    {
        this.conStr = conStr;
        using (SqlConnection con = new SqlConnection(conStr))
        {
            con.Open();
            using (SqlCommand cmd = new SqlCommand("SELECT * FROM tblTxRtes", con))
            {
                rates = new DataSet();
                new SqlDataAdapter(cmd).Fill(rates);
                Log.Write("Read " + rates.Tables[0].Rows.Count + " rates from database");
                if (rates.Tables[0].Rows.Count == 0)
                {
                    MailMessage msg = new MailMessage("important@legacy.org", "joe@legacy.com");
                    msg.Subject = "NO RATES IN DATABASE!!!!!";
                    msg.Priority = MailPriority.High;
                    new SmtpClient("mail.legacy.com", 9089).Send(msg);
                    Log.Write("No rates for taxes found in " + conStr);
                    throw new ApplicationException("No rates, Joe forgot to load the rates AGAIN!");
                }
            }
        }
    }

    public bool Process(XmlDocument transaction)
    {
        try
        {
            Hashtable tx2tot = new Hashtable();
            foreach (XmlNode o in transaction.FirstChild.ChildNodes)
            {
            restart:
                if (o.Attributes["type"].Value == "2")
                {
                    Log.Write("Type two transaction processing");
                    decimal total = decimal.Parse(o.Attributes["tot"].Value);
                    XmlAttribute attribute = transaction.CreateAttribute("tax");
                    decimal r = -1;
                    foreach (DataRow dataRow in rates.Tables[0].Rows)
                    {
                        if ((string)dataRow[2] == o.SelectSingleNode("//cust-details/state").Value)
                        {
                            r = decimal.Parse(dataRow[2].ToString());
                        }
                    }
                    Log.Write("Rate calculated and is: " + r);
                    o.Attributes.Append(attribute);
                    if (r == -1)
                    {
                        MailMessage msg = new MailMessage("important@legacy.org", "joe@legacy.com");
                        msg.Subject = "NO RATES FOR " + o.SelectSingleNode("//cust-details/state").Value + " TRANSACTION !!!!ABORTED!!!!";
                        msg.Priority = MailPriority.High;
                        new SmtpClient("mail.legacy.com", 9089).Send(msg);
                        Log.Write("No rate for transaction in tranasction state");
                        throw new ApplicationException("No rates, Joe forgot to load the rates AGAIN!");
                    }
                    tx2tot.Add(o.Attributes["id"], total * r);
                    attribute.Value = (total * r).ToString();
                }
                else if (o.Attributes["type"].Value == "1")
                {
                    //2006-05-02 just need to do the calc
                    decimal total = 0;
                    foreach (XmlNode i in o.ChildNodes)
                    {
                        total += ProductPriceByNode(i);
                    }
                    try
                    {
                        // 2007-02-19 not so simple, TX has different rule
                        if (o.SelectSingleNode("//cust-details/state").Value == "TX")
                        {
                            total *= (decimal)1.02;
                        }
                    }
                    catch (NullReferenceException)
                    {
                        XmlElement element = transaction.CreateElement("state");
                        element.Value = "NJ";
                        o.SelectSingleNode("//cust-details").AppendChild(element);
                    }
                    XmlAttribute attribute = transaction.CreateAttribute("tax");
                    decimal r = -1;
                    foreach (DataRow dataRow in rates.Tables[0].Rows)
                    {
                        if ((string)dataRow[2] == o.SelectSingleNode("//cust-details/state").Value)
                        {
                            r = decimal.Parse(dataRow[2].ToString());
                        }
                    }
                    if (r == -1)
                    {
                        MailMessage msg = new MailMessage("important@legacy.org", "joe@legacy.com");
                        msg.Subject = "NO RATES FOR " + o.SelectSingleNode("//cust-details/state").Value + " TRANSACTION !!!!ABORTED!!!!";
                        msg.Priority = MailPriority.High;
                        new SmtpClient("mail.legacy.com", 9089).Send(msg);
                        throw new ApplicationException("No rates, Joe forgot to load the rates AGAIN!");
                    }
                    attribute.Value = (total * r).ToString();
                    tx2tot.Add(o.Attributes["id"], total * r);
                    o.Attributes.Append(attribute);
                }
                else if (o.Attributes["type"].Value == "@")
                {
                    o.Attributes["type"].Value = "2";
                    goto restart;
                    // 2007-04-30 some bastard from northwind made a mistake and they have 3 months release cycle, so we have to
                    // fix this because they won't until sep-07
                }
                else
                {
                    throw new Exception("UNKNOWN TX TYPE");
                }
            }
            SqlConnection con2 = new SqlConnection(conStr);
            SqlCommand cmd2 = new SqlCommand();
            cmd2.Connection = con2;
            con2.Open();
            foreach (DictionaryEntry d in tx2tot)
            {
                cmd2.CommandText = "usp_TrackTxNew";
                cmd2.Parameters.Add("cid", transaction.SelectSingleNode("//cust-details/@id").Value);
                cmd2.Parameters.Add("tx", d.Key);
                cmd2.Parameters.Add("tot", d.Value);
                cmd2.ExecuteNonQuery();
            }
            con2.Close();
        }
        catch (Exception e)
        {
            if (e.Message == "UNKNOWN TX TYPE")
            {
                return false;
            }
            throw e;
        }
        return true;
    }

    private decimal ProductPriceByNode(XmlNode item)
    {
        using (SqlConnection con = new SqlConnection(conStr))
        {
            con.Open();
            using (SqlCommand cmd = new SqlCommand("SELECT * FROM tblProducts WHERE pid=" + item.Attributes["id"], con))
            {
                DataSet set = new DataSet();
                new SqlDataAdapter(cmd).Fill(set);
                return (decimal)set.Tables[0].Rows[0][4];

            }
        }
    }
}

Here is an interesting problem that I run into. I needed to produce an XML document for an external system to consume. This is a fairly complex document format, and there are a lot of scenarios to support. I began to test drive the creation of the XML document, but it turn out that I kept having to make changes as I run into more scenarios that invalidated previous assumptions that I made.

Now, we are talking about a very short iteration cycle, I might write a test to validate an assumption (attempting to put two items in the same container should throws) and an hour later realize that it is a legal, if strange, behavior. The tests became a pain point, I had to keep updating things because the invariant that they were based upon were wrong.

At that point, I decided that TDD was exactly the wrong approach for this scenario. Therefor, I decided that I am going to fall back to the old "trial and error" method. In this case, producing the XML and comparing using a diff tool.

The friction in the process went down significantly, because I didn't have to go and fix the tests all the time. I did break things that used to work, but I caught them mostly with manual diff checks.

So far, not a really interesting story. What is interesting is what happens when I decided that I have done enough work to consider most scenarios to be completed. I took all the scenarios and started generating tests for those. So for each scenario I now have a test that tests the current behavior of the system. This is blind testing. That is, I assume that the system is working correctly, and I want to ensure that it keeps working in this way. I am not sure what each test is doing, but the current behavior is assumed to be correct until proven otherwise..

Now I am back to having my usual safety net, and it is a lot of fun to go from zero tests to nearly five hundred tests in a few minutes.

This doesn't prove that the behavior of the system is correct, but it does ensure no regression and make sure that we have a stable platform to work from. We might find a bug, but then we can fix it in safety.

I don't recommend this approach for general use, but for this case, it has proven to be very useful.

I just wrote this piece of code:

class ExpressionInserterVisitor : DepthFirstVisitor
{
    public override bool Visit(Node node)
    {
        using(var con = new SqlConnection("data source=localhost;Initial Catalog=Test;Trusted_Connection=yes"))
        using (var command = con.CreateCommand())
        {
            con.Open();
            command.CommandText = "INSERT INTO Expressions (Expression) VALUES(@P1)";
            command.Parameters.AddWithValue("@P1", node.ToString());
            command.ExecuteNonQuery();
        }
        Console.WriteLine(node);
        return base.Visit(node);
    }
}

As you can imagine, this is disposable code, but why did I write that?

I run this code on the entire DSL code base that I have, and then started applying metrics to it. In particular, I was interested in trying to find repeated concepts that has not been codified.

For example, if this would have shown 7 uses of:

user.IsPreferred and order.Total > 500 and (order.PaymentMethod is Cash or not user.IsHighRisk)

Then this is a good indication that I have a business concept waiting to be discovered here, and I turn that into a part of my language:

IsGoodDealForVendor (or something like that)

Here we aren't interested in the usual code quality metrics, we are interested in business quality metrics :-) And the results were, to say the least, impressive.

This is a sample:

I am finding #Develop to be a treasure throve of components that can be used for DSL development... with the added bonus of being accessible and easy to use.

This is probably the best quote that I can find about the motivation for JFHCI:

Enabling developers to write "bad" code quickly and safely.

This post has really pissed me off:

It makes me sick to my stomach to think of all the good .NET projects that are now abandoned (or soon will be) because Microsoft seduced their authors away from doing anything that would actually benefit the .NET community.

Excuse !

Who exactly said that I owe something to anybody? Who exactly said that any of the guys who went to work for Microsoft (many of whom I consider friends) owe you something. The entire post is a whine about "I can't get the software I want for free".

Well, guess what, no one said it has to be free. Software has no right to be free. If anyone wants to stop dedicating significant amount of their time into free stuff, that is their decision, for their own reasons. Rhino Mocks is estimated at nine million dollars by Ohloh, I might decide to stop using it tomorrow, and you don't get a chance to protest that, or even to complain. Put simply, where exactly are your efforts? Where is your money and time?

Because unless you are a customer (in the sense of, money exchanged hands), you got stuff for free and now you complain because people aren't willing to do so anymore?

Now, leaving that aside, to the best of my knowledge, Castle, SubText, dasBlog and SubSonic are all alive and well and have received attention from the respective "seduced" authors.