VB.Net populating text boxes from text file - vb.net

Question

I'm creating an inventory management system where the data is stored in a text file. I'm able to save data to the text file, however on the tracker screen it should show current inventory such as: Manufacturer, Processor, Video, Form, RAM, etc. However, all my text boxes remain blank and I'm not sure why. It's not reading properly or updating the text.
frmTracker.vb
Private Sub txtManufacturer_TextChanged(sender As Object, e As EventArgs) Handles txtManufacturer.TextChanged
Dim objMyStreamReader = System.IO.File.OpenText("inventory.txt")
Dim strInventory = objMyStreamReader.ReadLine()
objMyStreamReader.Close()
txtManufacturer.AppendText(strInventory)
End Sub
This is how I'm currently saving the data to the text file.
frmItemEntry.vb
Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
Dim objMyStreamReader As System.IO.StreamReader
Dim objMyStreamWriter As System.IO.StreamWriter = System.IO.File.CreateText("inventory.txt")
Dim strInventory As String
objMyStreamWriter.WriteLine(txtManufacturerEntry.Text)
objMyStreamWriter.WriteLine(txtProcessorEntry.Text)
objMyStreamWriter.WriteLine(txtVideoEntry.Text)
objMyStreamWriter.WriteLine(txtFormEntry.Text)
objMyStreamWriter.WriteLine(txtRamEntry.Text)
objMyStreamWriter.WriteLine(txtVramEntry.Text)
objMyStreamWriter.WriteLine(txtHdEntry.Text)
objMyStreamWriter.WriteLine(chkWirelessEntry.CheckState)
objMyStreamWriter.Close()
Me.Close()
End Sub
Example from inventory.txt
Dell
i5
Nvidia
Desktop
8
4
600
0

Answer 1

To be honest, controls should never be used as the primary store for your data in a program. You should really be creating a class and a list of that class to store your data.
You can then read your data into the list from your file, and then, display it from there in your form.
There are several ways of navigating through the data and saving updates. The suggestion below uses buttons for next item and previous item, and a button to save update the file.
It's all pretty self explanatory, but if there's something your not sure about, please have a google and learn something new :-D
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
ReadDataFile()
DisplayItem(0)
End Sub
Private Class InventoryItem
Public Property Manufacturer As String
Public Property Processor As String
Public Property Video As String
Public Property FormFactor As String
Public Property Ram As String
Public Property VRam As String
Public Property Hd As String
Public Property Wireless As CheckState
Public Sub New()
Manufacturer = ""
Processor = ""
Video = ""
FormFactor = ""
Ram = ""
VRam = ""
Hd = ""
Wireless = CheckState.Unchecked
End Sub
End Class
Dim Inventory As New List(Of InventoryItem)
Dim currentItemIndex As Integer
Private Sub ReadDataFile()
Using objMyStreamReader As New StreamReader("k:\inventory.txt")
Do Until objMyStreamReader.EndOfStream
Dim newItem As New InventoryItem
newItem.Manufacturer = objMyStreamReader.ReadLine()
newItem.Processor = objMyStreamReader.ReadLine()
newItem.Video = objMyStreamReader.ReadLine()
newItem.FormFactor = objMyStreamReader.ReadLine()
newItem.Ram = objMyStreamReader.ReadLine()
newItem.VRam = objMyStreamReader.ReadLine()
newItem.Hd = objMyStreamReader.ReadLine()
Dim wirelessValue As String = objMyStreamReader.ReadLine()
If wirelessValue = "0" Then
newItem.Wireless = CheckState.Unchecked
ElseIf wirelessValue = "1" Then
newItem.Wireless = CheckState.Checked
End If
Inventory.Add(newItem)
Loop
End Using
End Sub
Private Sub SaveDataFile()
Using objMyStreamWriter As New System.IO.StreamWriter("k:\inventory.txt", False)
For Each item As InventoryItem In Inventory
objMyStreamWriter.WriteLine(item.Manufacturer)
objMyStreamWriter.WriteLine(item.Processor)
objMyStreamWriter.WriteLine(item.Video)
objMyStreamWriter.WriteLine(item.FormFactor)
objMyStreamWriter.WriteLine(item.Ram)
objMyStreamWriter.WriteLine(item.VRam)
objMyStreamWriter.WriteLine(item.Hd)
If item.Wireless = CheckState.Checked Then
objMyStreamWriter.WriteLine("1")
Else
objMyStreamWriter.WriteLine(0)
End If
Next
End Using
End Sub
Private Sub DisplayItem(index As Integer)
With Inventory(index)
txtManufacturerEntry.Text = .Manufacturer
txtProcessorEntry.Text = .Processor
txtVideoEntry.Text = .Video
txtFormEntry.Text = .FormFactor
txtRamEntry.Text = .Ram
txtVramEntry.Text = .VRam
txtHdEntry.Text = .Hd
chkWirelessEntry.CheckState = .Wireless
End With
End Sub
Private Sub BtnUpdateItem_Click(sender As Object, e As EventArgs) Handles BtnUpdateItem.Click
With Inventory(currentItemIndex)
.Manufacturer = txtManufacturerEntry.Text
.Processor = txtProcessorEntry.Text
.Video = txtVideoEntry.Text
.FormFactor = txtFormEntry.Text
.Ram = txtRamEntry.Text
.VRam = txtVramEntry.Text
.Hd = txtHdEntry.Text
.Wireless = chkWirelessEntry.CheckState
End With
SaveDataFile()
End Sub
Private Sub BtnPreviousItem_Click(sender As Object, e As EventArgs) Handles BtnPreviousItem.Click
If currentItemIndex > 0 Then
currentItemIndex -= 1
DisplayItem(currentItemIndex)
End If
End Sub
Private Sub BtnNextItem_Click(sender As Object, e As EventArgs) Handles BtnNextItem.Click
If currentItemIndex < Inventory.Count - 1 Then
currentItemIndex -= 1
DisplayItem(currentItemIndex)
End If
End Sub

Answer 2

First change the format of your text file.
Dell,i5,Nvidia,Desktop,8,2,600,True
Acer,i7,Intel,Desktop,16,4,1GB,True
HP,Pentium,Diamond Viper,Desktop,4,2,200,False
Surface Pro,i7,Intel,Laptop,8,2,500,True
Each line is a record and each field in the record is separated by a comma (no spaces so we don't have to .Trim in code) (a space within a field is fine, notice Surface Pro).
Now it is easier to read the file in code.
This solution uses a BindingSource and DataBindings. This simplifies Navigation and editing and saving the data.
Public Class Form5
Private bs As BindingSource
Private dt As New DataTable
#Region "Set Up the Form"
Private Sub Form5_Load(sender As Object, e As EventArgs) Handles MyBase.Load
AddColumnsToDataTable()
FillDataTable()
AddDataBindings()
End Sub
Private Sub AddColumnsToDataTable()
'Prepare the DataTable to hold data
dt.Columns.Add("Manufacturer", GetType(String))
dt.Columns.Add("Processor", GetType(String))
dt.Columns.Add("Video", GetType(String))
dt.Columns.Add("Form", GetType(String))
dt.Columns.Add("RAM", GetType(String))
dt.Columns.Add("VRAM", GetType(String))
dt.Columns.Add("HD", GetType(String))
dt.Columns.Add("Wireless", GetType(Boolean))
End Sub
Private Sub FillDataTable()
'ReadAllLines returns an array of the lines in a text file
'inventory.txt is stored in the bin\Debug folder of your project
'This is the current directory so it does not require a full path.
Dim lines = File.ReadAllLines("inventory.txt")
'Now it is easy to split each line into fields by using the comma
For Each line As String In lines
'Split returns an array of strings with the value of each field
Dim items = line.Split(","c)
'Each item in the array can be added as a field to the DataTable row
dt.Rows.Add(items(0), items(1), items(2), items(3), items(4), items(5), items(6), CBool(items(7)))
'Notice that the last element is changed from a string to a boolean. This is
'the Wireless field which is bound to the check box. The string "True" or "False" is
'changed to a Boolean so it can be used as the .Checked property (see bindings)
Next
End Sub
Private Sub AddDataBindings()
'Create a new instance of the BindingSource class
bs = New BindingSource()
'Set the DataSource to the DataTable we just filled
bs.DataSource = dt
'Now you can set the bindings of each control
'The .Add method takes (Name of Property to Bind, the BindingSource to use, The Field name
'from the DataTable.
txtForm.DataBindings.Add("Text", bs, "Form")
txtHd.DataBindings.Add("Text", bs, "HD")
txtManufacturer.DataBindings.Add("Text", bs, "Manufacturer")
txtProcessor.DataBindings.Add("Text", bs, "Processor")
txtRam.DataBindings.Add("Text", bs, "RAM")
txtVideo.DataBindings.Add("Text", bs, "Video")
txtVram.DataBindings.Add("Text", bs, "VRAM")
'Notice on the CheckBox we are using the Checked property.
chkWireless.DataBindings.Add("Checked", bs, "Wireless")
End Sub
#End Region
Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
'Add a blank row to the DataTable
'A Boolean is like a number, a String can be Nothing but a Boolean must
'have a value so we pass in False.
dt.Rows.Add(Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, False)
'Find the position of the last row
Dim i As Integer = bs.Count - 1
'Move to the new empty row
bs.Position = i
End Sub
#Region "Navigation Code"
Private Sub btnPrevious_Click(sender As Object, e As EventArgs) Handles btnPrevious.Click
'The binding source Position determins where in the data you are
'It starts at zero
If bs.Position = 0 Then
MessageBox.Show("This is the first item.")
Return 'This exits the sub, you can use Exit Sub in vb
'but Return is common in other languages so it is good to learn
Else
'As the position of the BindingSource changes the boud TextBoxes
'change their data.
bs.Position = bs.Position - 1
End If
End Sub
Private Sub btnNext_Click(sender As Object, e As EventArgs) Handles btnNext.Click
' If you are not at the end of the list, move to the next item
' in the BindingSource.
If bs.Position + 1 < bs.Count Then
bs.MoveNext()
' Otherwise, move back to the first item.
Else
bs.MoveFirst()
End If
End Sub
#End Region
#Region "Save the Data"
Private Sub SaveDataTable()
'Resave the whole file if this was a real app you would use a database
Dim sb As New StringBuilder
'A string builder keeps the code from creating lots of new strings
'Strings are immutable (can't be changed) so every time you think you are
'changing a string, you are actually creating a new one.
'The string builder is mutable (changable)
For Each row As DataRow In dt.Rows
'The ItemsArray returns an array of objects containing all the
'values in each column of the data table.
Dim rowValues = row.ItemArray
'This is a bit of Linq magic that turns the values (objects) into strings
'Underneath it is performing a For loop on each object in the array
Dim strRowValues = From o In rowValues
Select Convert.ToString(o)
'Now that we have strings we can use the String.Join with the comma
'to get the format of the text file
sb.AppendLine(String.Join(",", strRowValues))
Next
'Finally we change the StringBuilder to a real String
'The inventory.txt is stored in the bin\Debug directory so it is current directory
'no additional path required
File.WriteAllText("inventory.txt", sb.ToString)
End Sub
Private Sub Form5_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
'Because our binding is two-way any additions or changes to the text
'in the text boxes or check box are reflected in the DataTable.
SaveDataTable()
End Sub
#End Region
End Class
Once you remove the comments, there is really very little code here. The #Region...#End Region tags make it easy to collapse code sections you are not working on and find areas quickly.