Repeating Habits

I had a student's code not working. He was getting this error: A first chance exception of type 'System.FormatException' occurred in mscorlib.dll. Goggleing the error was no help. My first reaction was to take my working code and compare it to his broken code. See the examples below. Can you see the difference? I did not. The bad habit I had was taking my working code and comparing it line by line after the lines by line. I have fixed many student errors this way. It did not work this time. I also let the student see the code also. I was unable to see the error but the student found the error later.

Working Code:

btnDisplayCost_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDisplayCost.Click

Dim strEnterNumberOfTickets As String

Dim intEnterNumberOfTickets As Integer

Dim decTotalCostOfTickets As Decimal

strEnterNumberOfTickets = Me.txtEnterNumberOfTickets.Text

intEnterNumberOfTickets = Convert.ToInt32(strEnterNumberOfTickets)

decTotalCostOfTickets = intEnterNumberOfTickets * cdecTotalCostOfTickets

Me.lblTotalCostOfTickets.Text = decTotalCostOfTickets.ToString("C")

Bad Code:

frmConcertTickets_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

Dim strEnterNumberOfTickets As String

Dim intEnterNumberOfTickets As Integer

Dim decTotalCostOfTickets As Decimal

strEnterNumberOfTickets = Me.txtEnterNumberOfTickets.Text

intEnterNumberOfTickets = Convert.ToInt32(strEnterNumberOfTickets)

decTotalCostOfTickets = intEnterNumberOfTickets * cdecTotalCostOfTickets

Me.lblTotalCostOfTickets.Text = decTotalCostOfTickets.ToString("C")