Recollection of my journey with Business Rules - Part 1

There are lot’s of reasons why one writes blog posts. One of them is this: so that he will have something to laught at when he gets older.

This post might be one of those posts I will laugh at when I get older… It sounds like I’m bragging about my old but insignificant work! Who cares, right? It might be insignificant to others, but it was significant to me.

So here we go…

In my five years of experience working as a programmer I have come into a deeper appreciation of the importance of separating the business rules from the other parts of a software system.

Since college I’ve been on search on how to best structure a software system.

I remember encountering this idea of 3-layers architecture in college — Presentation layer, Business Logic layer (BLL), and Data Access layer (DAL). But during that time, I do not yet fully understand the “why” part of the separation.

Today, I already understand why: the separation makes the software soft, that is easy to maintain. Maintainability is important because, like what they say, maintenance comprises 80% of the life of a software system.

I remember using this 3-layers thing in one, and only one, of my projects at school. What I remember doing in that project is placing the validation in the BLL, and placing all the SQL in the DAL.

“I wonder what I really did in that project…“

Sometimes I just want to know what happened in the past.

…So I tried to look for that project in my old files.

Tada!!! I found it: “StudInfoSys_VB.NETProj - 4.8”

There!… This part contains the validation I was talking about in a previous post.

Public Class StudentBLL
    ...
    Public Sub InsertStudent(ByVal FirstName As String, ...)
        ...
        If FirstName.Trim() = "" Then
            Throw New Exception("First Name is required")
        End If
        If LastName.Trim() = "" Then
            Throw New Exception("Last Name is required")
        End If
        
        studDAL.OpenConnection(connectionString)
        studDAL.InsertStudent(FirstName, ...)
        studDAL.CloseConnection()
    End Sub
    ...
End Class

Public Class StudentDAL
    ...
    Public Sub InsertStudent(ByVal FirstName As String, ...)
        Dim sqlstr As String = String.Format("INSERT INTO Students " & ...

        Using cmd As New OleDbCommand(sqlstr, Me.oledbConn)
            cmd.ExecuteNonQuery()
        End Using
    End Sub
    ...
End Class

Modified: Thursday, ‎16 ‎February ‎2012, ‏‎11:43:22 PM

It was written in VB.NET?… in 2012?

Why? I think during this time, I am already using C# as my primary programming language!…

Maybe it was a requirement at school to use VB.NET? I’m not sure… But maybe I just wanted to challenge myself whether I can still write in VB.NET during that time? Perhaps… I’m not sure.

But perhaps this project is not mine!?…

I tried to look for some hints in the project so that I can be sure that this truly is mine…

Public Class StudentBLL

...
...

'Created: February 17, 2012 7:00 PM to 2:00 AM the next day

That sounds like me…

And it truly is written in 2012!!

But I’m sure that I knew about this 3-layers thing before 2012!…

But I remember using it only in one and only one project! And because this project is confirmed as mine, this must be that project where I tried to use this 3-layers thing!

Hmmmm… Something must be wrong…

Ahh!!!

I found another project… written in C#… created in 2010! It has a DAL, but no BLL: “StudInfoSys(TypedDataSets)”

public partial class StudentForm : Form
{

// [in line 719]
    private void subjectIDComboBox_SelectedValueChanged(object sender, EventArgs e)
    {
        try
        {
            if (((ComboBox)sender).SelectedIndex == -1)
            {
                descriptiveTitleTextBox.Text = "";
                return;
            }

            string currSubjectID = subjectIDComboBox.Text;

            var subjects = from s in studInfoSysDataSet.Subjects
                            where s.SubjectID == currSubjectID
                            select s;

            //Descriptive title of currently selected SubjectID
            if (subjects != null)
            {
                descriptiveTitleTextBox.Text = subjects.Single().DescriptiveTitle;
            }
        }
        catch (InvalidOperationException)
        {
            this.regSubjectsBindingNavigatorPositionItem.Text = "NONE";
        }
    }
}

So it is confirmed that before 2012 I am already familiar with C#.

But Look at that mess… 700 lines of code… I packed everything in one Form… and the presentation layer knows about DataSets!”

In a good architecture, the DataSets are not supposed to be exposed to the presentation layer. But of course, I was naive during that time.

And also during that time, I liked the drag-and-drop things that Visual Studio provides … It makes the life of a programmer easier (or so I thought). You just drag a GridView, change some properties in it to connect it to the database, and wa-la… you now have a working application!

In that kind of environment, with the drag-and-drop thing, the presentation layer is tightly coupled to the data-access layer. Perhaps there was another way of doing it, without the tight coupling, but I think this was the only way I know how to do it during that time.

Of course I later understood that these drag-and-drop things are evil… I mean, you would not want to (ab)use it if you want your app to be maintainable (or something like that).

The End

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