Question

Question: Why is it that holdDate under function Check(), show “Nothing” while debugging, I was passing by reference. What am i missing guys??

Description of problem:

I have a class named Wallet, I created instance of that class in my main code by passing three parameters (Objects already on my form that will be populated with data from the user at a later time, not right away):

Dim myWallet As New Wallet(DataGridView1, DateTimePicker1, "StatementsLog.dat")

At run time I get this:

As you can see, the object that was suppose to reference the original object from the form is empty? I thought that if i passed by reference (as shown below) that the object will always show the data, and that would allow me to read it as shown in the screenshot above:

Public Sub New(ByRef Data As DataGridView, ByRef _Date As DateTimePicker, Optional ByVal StatementsFileName As String = "defaultLog.txt")
  'This constructor takes in references to use in class as private
  holdPath = StatementsFileName
  holdData = Data
  holdDate = _Date
End Sub

Here’s what i got so far for Class Wallet:

Option Strict On
Imports System
Imports System.IO

Public Class Wallet

  Private lcheckNumber As Integer = Nothing
  Private lcheckAmount As Decimal = Nothing
  Private ldepositAmount As Decimal = Nothing
  Private lfee As Decimal = Nothing
  Private lDescription As String = Nothing

  Private holdDate As New DateTimePicker
  Private holdData As New DataGridView
  Private holdPath As String = vbNullString

  'Default Constructor
  Public Sub New()
    holdPath = "defaultLog.txt"
  End Sub

  Public Sub New(ByRef _Data As DataGridView, ByRef _Date As DateTimePicker, Optional ByVal StatementsFileName As String = "defaultLog.txt")
    'This constructor takes in references to use in class as private
    holdPath = StatementsFileName
    holdData = _Data
    holdDate = _Date
  End Sub

  'Function Check - Deduct the amount from account and returns current balance.
  Public Function Check(ByVal CheckNumber As Integer, ByVal CheckAmount As Decimal, ByVal Description As String) As Decimal
    Try
      lcheckNumber = CheckNumber
      lcheckAmount = CheckAmount
      lDescription = Description
      lfee = 0D

      Dim _file As New FileStream(holdPath, FileMode.Append, FileAccess.Write)
      Using file As New StreamWriter(_file)
         file.WriteLine(holdDate.Value.ToString & "," & lDescription.ToString & "," & lcheckNumber.ToString & "," & lfee.ToString & "," & lcheckAmount.ToString)
      End Using
    Catch e As IOException
      MessageBox.Show(e.ToString)
    End Try

    Return 0D
  End Function

Form1 Code

Option Strict On
Imports WalletProgram.Wallet

Public Class Form1
    Dim myWallet As New Wallet(DataGridView1, DateTimePicker1, "StatementsLog.dat")


    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        optCheck.Checked = True

        'Just test data for DataGridView1
        DataGridView1.Rows.Add(New String() {"12/21/1986", "Test", "44554", "44.22", "45.12"})
    End Sub

    Private Sub cmdAddTransaction_Click(sender As System.Object, e As System.EventArgs) Handles cmdAddTransaction.Click
        If optCheck.Checked Then
            lblAvailableFunds.Text = FormatCurrency(myWallet.Check(CInt(Trim(txtCheck.Text)), CDec(Trim(txtMoney.Text)), txtDescription.Text))
        End If
    End Sub
End Class

Answer 1

The problem is most likely here:

Public Class Form1
  Dim myWallet As New Wallet(DataGridView1, DateTimePicker1, "StatementsLog.dat")

That will compile, but those objects haven’t been created yet since it happens before the form’s InitializeComponent routine gets called.

Try changing the declaration to this:

Public Class Form1
  Dim myWallet As Wallet

  Protected Overrides Sub OnLoad(e As System.EventArgs)
    _Wallet = New Wallet(DataGridView1, DateTimePicker1)
    MyBase.OnLoad(e)
  End Sub

End Class

where the Wallet class gets created after the controls have been created.