VB.net: Input string not correct format? - vb.net

Question

Hey guys I have been having this crashing problem with my program.
I am trying to create a program where it calculates a persons account balance by inputting their beginning balance, credit limit, total charges, and total credits. In this case I am having specific problems with the Total Charges and Total Credits Code.
I have a message box set up to where if the Total Charges and total credits box are blank it will say "please enter a numeric value for ....". The problem is that when I do run it and enter a blank, the message shows up and then the program crashes.
After crashing, the The program then highlights in yellow the specific conversion code (in this case: decTotalCharges = Convert.ToDecimal(txtTotalCharges.Text)) and the error says Input string was not in correct format.
What's going on, I converted it into a correct format right? (decimal to decimal?). Here's an in depth look at my code:
Public Class frmEndingBalance
'Declare module level variables
Dim mdecEndingBalance As Decimal
Dim mdecAllCharges As Decimal
Dim mdecAllCredits As Decimal
Dim mintCustomersOverLimit As Integer
Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
'clears the form
'clears the labels
txtAccountNumber.Text = ""
txtBeginningBalance.Text = ""
txtTotalCharges.Text = ""
txtTotalCredits.Text = ""
txtCreditLimit.Text = ""
lblEndingBalance.Text = ""
lblCreditMessage.Text = ""
lblAllCharges.Text = ""
lblAllCredits.Text = ""
lblCustomersOverLimit.Text = ""
lblCreditMessage.Text = ""
'clear the textboxes
txtAccountNumber.Clear()
txtBeginningBalance.Clear()
txtTotalCredits.Clear()
txtTotalCharges.Clear()
txtCreditLimit.Clear()
'clear module level variables
mdecEndingBalance = 0
mdecAllCharges = 0
mdecAllCredits = 0
mintCustomersOverLimit = 0
End Sub
Private Sub btnCalculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalculate.Click
'Declare Variables
Dim intAccountNumber As Integer
Dim intBeginningBalance As Integer
Dim decTotalCharges As Decimal
Dim decTotalCredits As Decimal
Dim decCreditLimit As Decimal
Dim mdecEndingBalance As Decimal 'Beginning Balance + Charges - Credits()
Dim decCreditMessage As Decimal
'check for numeric
If IsNumeric(txtAccountNumber.Text) = False Then 'value is not numeric
MessageBox.Show("You can't enter anything blank!")
Exit Sub
End If
'convert to a numeric data type
intAccountNumber = Convert.ToInt32(txtAccountNumber.Text)
'check for numeric
If String.IsNullOrEmpty(txtBeginningBalance.Text) Then MessageBox.Show("Beginning Balance Cannot Be Blank!")
'check for everything else
If IsNumeric(txtBeginningBalance.Text) = False Then 'Value is not numeric
MessageBox.Show("Please enter a numeric value for Beginning Balance!")
Exit Sub
End If
'convert to a numeric data type
intBeginningBalance = Convert.ToInt32(txtBeginningBalance.Text)
'check for numeric
If IsNumeric(txtTotalCharges.Text) = False Then 'value is not numeric
MessageBox.Show("Please enter a numeric value for Total Charges!")
End If
'convert
decTotalCharges = Convert.ToDecimal(txtTotalCharges.Text)
'check for 0 or positive
If decTotalCharges < 0 Then
MessageBox.Show("Please enter a positive value or zero for number of Total Charges!")
Exit Sub
End If
'check for numeric
If IsNumeric(txtTotalCredits.Text) = False Then 'value is not numeric
MessageBox.Show("Please enter a numeric value for Total Credits")
End If
'convert to a numeric data type
decTotalCredits = Convert.ToDecimal(txtTotalCredits.Text)
'check for 0 or positive
If decTotalCredits < 0 Then
MessageBox.Show("Please enter a positive value or zero for total credits!")
End If
'check numeric
If IsNumeric(txtCreditLimit.Text) = False Then 'value is not numeric
MessageBox.Show("Please enter a numeric value for the Credit Limit!")
End If
'convert to a numeric data type
decCreditLimit = Convert.ToDecimal(txtCreditLimit.Text)
'check for a 0 or positive
If decCreditLimit < 0 Then
MessageBox.Show("Please enter a positive value or zero for Credit Limit!")
End If
'check for customers over limit
decCreditMessage = decCreditLimit - (mdecEndingBalance)
'running totals
mdecAllCharges += decTotalCharges
mdecAllCredits += decTotalCredits
'calculate Ending Balance
mdecEndingBalance = Convert.ToDecimal(intBeginningBalance + decTotalCharges - (decTotalCredits))
'display outputs
lblEndingBalance.Text = mdecEndingBalance.ToString("c")
lblAllCharges.Text = mdecAllCharges.ToString("c")
lblAllCredits.Text = mdecAllCredits.ToString("c")
lblCustomersOverLimit.Text = mintCustomersOverLimit.ToString("n0")
End Class
Any Help would be greatly appreciated!
Thanks

Answer 1

You've missed Exit Sub out of the test
If IsNumeric(txtTotalCharges.Text) = False Then 'value is not numeric
MessageBox.Show("Please enter a numeric value for Total Charges!")
End If
You've done it in a few other places as well (as have we all , in fact as do we all :( ). Be worth refactoring with a little helper method or something similar.
If IsValidDecimal(txtTotalCharges.Text, "Total Charges")
' etc
End If