Saving and reading files on Visual basic - vb.net

Question

Hi I'm creating a "Toilet paper tracker" on visual basic and I'm struggling with saving and reading files, I know I am missing stuff. The user should be able to login and input a threshold and when reached a warning will pop up saying "buy more toilet paper" (i haven't coded this yet) and the user can add to create a total and subtract from it too. The user should also be able to save the total to a file and I want the program to be able to read the file and change the total if the user wants to add or subtract again. It would be greatly appreciated if you pointed me in the right direction, I'm only young so it's relatively simple. Here is my program :)
Imports System.IO
Public Class frmTPT
Private Sub TPT_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Call loadchangetotal()
End Sub
Sub loadchangetotal()
cboChange.Items.Add("Add to Total")
cboChange.Items.Add("Subtract from Total")
End Sub
Private Sub cboVenue_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cboChange.SelectedIndexChanged
If cboChange.Text = "Add to Total" Then
Dim frmChangeACopy As New frmChangeA
frmChangeACopy.Show()
Me.Hide()
ElseIf cboChange.Text = "Subtract from Total" Then
Dim frmChangeSCopy As New frmChangeS
frmChangeSCopy.Show()
Me.Hide()
End If
End Sub
Private Sub btnReturn_Click(sender As Object, e As EventArgs)
Dim frmLoginCopy As New frmLogin
frmLoginCopy.Show()
Me.Hide()
End Sub
Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click
txtThreshold.Text = ""
cboChange.Text = ""
txtTotal.Text = ""
End Sub
Private Sub ExitToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles ExitToolStripMenuItem.Click
End
End Sub
Private Sub LogoutToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles LogoutToolStripMenuItem.Click
Dim frmLoginCopy As New frmLogin
frmLoginCopy.Show()
Me.Hide()
End Sub
Private Sub btnReadTotal_Click(sender As Object, e As EventArgs) Handles btnReadTotal.Click
Dim FileReader As StreamReader
Dim result As DialogResult
result = OpenFileDialog1.ShowDialog
If result = DialogResult.OK Then
FileReader = New StreamReader(OpenFileDialog1.Filename)
txtFileContent.Text = FileReader.ReadToEnd() 'i want to be able to read a
'previously saved total so that
FileReader.Close() 'it can be used to find the new total
'after it has been added to
End If 'or subtratced
End Sub
Private Sub SaveToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles SaveToolStripMenuItem.Click
Call SaveFile()
End Sub
Private Sub btnDisplay_Click(sender As Object, e As EventArgs) Handles btnDisplay.Click
Dim A, S, NewTotal As Integer
A = Val(frmChangeA.txtAdd.Text)
S = Val(frmChangeS.txtSubtract.Text)
NewTotal = A - S 'I want to be able to load a previously saved total if one exists and add and
'subtract from it
End Sub
End Class
Sub SaveFile()
Dim FileWriter As StreamWriter
Dim results As DialogResult
results = SaveFileDialog1.ShowDialog
If results = DialogResult.OK Then
FileWriter = New StreamWriter(SaveFileDialog1.FileName, False)
FileWriter.Write(txtFileContent.Text) ' is txtFileContent supposed to be
' the name of my textbox?
FileWriter.Close()
End If
End Sub
Design

Answer 1

You didn't mention if you were using .Net Core or 4.x. If the later, you can sometimes use the Insert Snippet functionality to learn how to do common tasks. For example in this case you could right click in the code editor and select Insert Snippet then Fundamentals then File System and finally Write text to a file. This will result in the following VB code:
My.Computer.FileSystem.WriteAllText("C:\Test.txt", "Text", True)
Unfortunately, this option doesn't work with .Net core since the My namespace wasn't ported to core.

Answer 2

The key point of this problem lies in reading and writing data from text. It is a clear idea to write two methods to achieve read and write.
You can refer to the following code. The two methods in the following example are WriteTotal(), ReadTotal().
Design:
Public Class Form1
Dim Oldtotal As Integer
Dim Newtotal As Integer
Private Sub btnLoadTotal_Click(sender As Object, e As EventArgs) Handles btnLoadTotal.Click
WriteTotal()
ReadTotal()
End Sub
Private Sub btnUpdateTotal_Click(sender As Object, e As EventArgs) Handles btnUpdateTotal.Click
cboChange.Text = Nothing
WriteTotal()
ReadTotal()
MsgBox("Inventory updated")
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
cboChange.SelectedIndex = 0
ReadTotal()
End Sub
Sub WriteTotal()
Using swriter As IO.StreamWriter = New IO.StreamWriter("D:/paperstore.txt", False, System.Text.Encoding.UTF8)
If cboChange.Text = "Add to Total" Then
Newtotal = Oldtotal + CType(txtThreshold.Text, Integer)
swriter.WriteLine(Newtotal)
ElseIf cboChange.Text = "Subtract from Total" Then
If CType(txtThreshold.Text, Integer) > Oldtotal Then
swriter.WriteLine(Oldtotal)
MsgBox("buy more toilet paper")
Else
Newtotal = Oldtotal - CType(txtThreshold.Text, Integer)
swriter.WriteLine(Newtotal)
End If
Else
swriter.WriteLine(txtTotal.Text)
End If
End Using
End Sub
Sub ReadTotal()
Using sreader As IO.StreamReader = New IO.StreamReader("D:/paperstore.txt", System.Text.Encoding.UTF8)
Try
Oldtotal = sreader.ReadLine()
txtTotal.Text = Oldtotal
Catch ex As Exception
MsgBox(ex.Message)
End
End Try
End Using
End Sub
End Class