How to save many object (with the same class) to txt file and binding those object with listbox VB.NET - vb.net

Question

I try to program a simple project to save data to txt file, read it and use binding data to show it. My project like this.
When I add ID Person to "Add ID" textbox (Textbox which near Button "Add ID"). It will add ID to Listbox and "ID Name" textbox. With this IDName, I insert FirstName and LastName for first person and Save Person's Name. Then, I Add new ID in "Add ID" textbox and fill First,last name and save it again
I refer this page http://vbnetsample.blogspot.de/2007/12/serialize-deserialize-class-to-file.html?m=1 to save and read data to txt file. It's run ok. But my problem is that when I save Person 2 with ID 2, Person 1 is overwrited. I think I can save Person to List Person. But it will make difficult when I want to update any Person's data. I don't know whether Is there any way to save and update each person. And by the way How can I show data by binding data in listbox.
Here is my code
Imports System.Runtime.Serialization.Formatters.Binary
Imports System.IO
Public Class Form1
Public pPerson As New Person
'Serialize and Save Data to txt file
Private Sub SaveButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SaveButton.Click
pPerson.IDName = IDNameTextBox.Text
pPerson.FirstName = FirstNameTextBox.Text
pPerson.LastName = LastNameTextBox.Text
Dim fs As FileStream = New FileStream("C:\Users\Bruce\Desktop\test.txt", FileMode.OpenOrCreate)
Dim bf As New BinaryFormatter()
bf.Serialize(fs, pPerson)
fs.Close()
End Sub
'Deserialize and Read Data from txt file
Private Sub ReadButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ReadButton.Click
If FileIO.FileSystem.FileExists("C:\Users\Bruce\Desktop\test.txt") Then
Dim fsRead As New FileStream("C:\Users\Bruce\Desktop\test.txt", FileMode.Open)
Dim bf As New BinaryFormatter()
Dim objTest As Object = bf.Deserialize(fsRead)
fsRead.Close()
IDNameTextBox.Text = objTest.IDName
FirstNameTextBox.Text = objTest.FirstName
LastNameTextBox.Text = objTest.LastName
End If
End Sub
Private Sub AddIDButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AddIDButton.Click
ListBox1.Items.Insert(0, AddIDTextBox.Text)
IDNameTextBox.Text = AddIDTextBox.Text
End Sub
End Class
'Create Class Person
<System.Serializable()>
Public Class Person
Private m_sIDName As String
Private m_sFirstName As String
Private m_sLastName As String
Public Sub New()
End Sub
Public Property IDName() As String
Get
Return Me.m_sIDName
End Get
Set(ByVal value As String)
Me.m_sIDName = value
End Set
End Property
Public Property FirstName() As String
Get
Return Me.m_sFirstName
End Get
Set(ByVal value As String)
Me.m_sFirstName = value
End Set
End Property
Public Property LastName() As String
Get
Return Me.m_sLastName
End Get
Set(ByVal value As String)
Me.m_sLastName = value
End Set
End Property
End Class

Answer 1

To me it seems like the issue here is
Dim fs As FileStream = New FileStream("C:\Users\Bruce\Desktop\test.txt", FileMode.OpenOrCreate)
you have to change it to this:
If not File.Exists("C:\Users\Bruce\Desktop\test.txt") Then
File.create("C:\Users\Bruce\Desktop\test.txt")
End If
Dim fs As FileStream = New FileStream("C:\Users\Bruce\Desktop\test.txt", FileMode.Append)
The whole problem was that your file was simply open (or created if it was not there before) and being written from the first line.By using FileMode.Append your File will be opened and anything new will be tried to be written at the end of the file.
Let me know if this worked :)