Need assistance with writing to a CSV file and saving entries - vb.net

Question

I am creating a student test score application which shows student averages, class averages (I haven't done this part yet) and can search for a particular student which shows up in the text boxes.
Can someone please tell me how to write the test scores and name of student entered into the text boxes to an Excel CSV file?
Also the save button keeps clearing all the enteries to the CSV file when I click on it. If anyone could tell me whats going on there, that would be great.
Imports System.IO
Public Class Form1
Structure Students
Dim StudentName As String
Dim Test1 As Double
Dim Test2 As Double
Dim Test3 As Double
Dim Test4 As Double
Dim Test5 As Double
End Structure
Dim StudentCounter As Integer = 0
Dim MyStudentArray(StudentCounter) As Students
Private Sub LoadDataFromFileToArray()
Dim TextFile As New System.IO.StreamReader(“..\..\StudentDataFile.csv”)
Dim strStudentData As String
strStudentData = TextFile.ReadLine()
Do Until strStudentData Is Nothing
lstAllStudentData.Items.Add(strStudentData)
WriteToArray(strStudentData)
strStudentData = TextFile.ReadLine()
Loop
TextFile.Close()
End Sub
Private Sub WriteToArray(ByVal CurrentLine)
Dim Values() As String = Split(CurrentLine, ",")
ReDim Preserve MyStudentArray(StudentCounter)
MyStudentArray(StudentCounter).StudentName = Values(0)
MyStudentArray(StudentCounter).Test1 = (Values(1))
MyStudentArray(StudentCounter).Test2 = (Values(2))
MyStudentArray(StudentCounter).Test3 = (Values(3))
MyStudentArray(StudentCounter).Test4 = (Values(4))
MyStudentArray(StudentCounter).Test5 = (Values(5))
StudentCounter += 1
End Sub
Private Sub btnAddStudent_Click(sender As Object, e As EventArgs) Handles btnAddStudent.Click
ReDim Preserve MyStudentArray(StudentCounter)
MyStudentArray(StudentCounter).Test1 = CDbl(txtTest1.Text)
MyStudentArray(StudentCounter).Test2 = CDbl(txtTest1.Text)
MyStudentArray(StudentCounter).Test3 = CDbl(txtTest1.Text)
MyStudentArray(StudentCounter).Test4 = CDbl(txtTest1.Text)
MyStudentArray(StudentCounter).Test5 = CDbl(txtTest1.Text)
MyStudentArray(StudentCounter).StudentName = (txtStudentName.Text)
StudentCounter += 1
End Sub
Private Sub CalculateIndividual()
Dim AverageScore As Double = 0
Dim Test1 As Double = CDbl(txtTest1.Text)
Dim Test2 As Double = CDbl(txtTest2.Text)
Dim Test3 As Double = CDbl(txtTest3.Text)
Dim Test4 As Double = CDbl(txtTest4.Text)
Dim Test5 As Double = CDbl(txtTest5.Text)
Dim AverageGrade As String
AverageScore = (Test1 + Test2 + Test3 + Test4 + Test5) / 5
lblScoreOutput.Text = AverageScore
lblScoreOutput.Visible = True
Select Case AverageScore
Case > 90
AverageGrade = "A+"
Case 80 To 90
AverageGrade = "A"
Case 70 To 80
AverageGrade = "B"
Case 60 To 70
AverageGrade = "C"
Case 50 To 60
AverageGrade = "D"
Case 35 To 50
AverageGrade = "E"
Case Else
AverageGrade = "UG"
End Select
lblLetterOutput.Text = AverageGrade
lblLetterOutput.Visible = True
End Sub
Private Sub Form_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
Dim response As MsgBoxResult
response = MsgBox("Do you want to close Student Calculator", MsgBoxStyle.Question + MsgBoxStyle.YesNo, "Confirm")
If response = MsgBoxResult.Yes Then
Me.Dispose()
ElseIf response = MsgBoxResult.No Then
e.Cancel = True
Exit Sub
End If
End Sub
Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
Dim response As MsgBoxResult
response = MsgBox("Do you want to close Student Calculator?", MsgBoxStyle.Question + MsgBoxStyle.YesNo, "Confirm")
If response = MsgBoxResult.Yes Then
Me.Dispose()
ElseIf response = MsgBoxResult.No Then
Exit Sub
End If
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
lstAllStudentData.Items.Clear()
LoadDataFromFileToArray()
lstAllStudentData.Items.Clear()
LoadDataFromFileToArray()
Dim MySource As New AutoCompleteStringCollection()
For StudentCounter = 0 To StudentCounter - 1
MySource.Add(MyStudentArray(StudentCounter).StudentName)
Next
With txtSearch
.AutoCompleteCustomSource = MySource
.AutoCompleteMode = AutoCompleteMode.SuggestAppend
.AutoCompleteSource = AutoCompleteSource.CustomSource
.Visible = True
Me.Controls.Add(txtSearch)
End With
End Sub
Private Sub lstAllStudentData_SelectedIndexChanged(sender As Object, e As EventArgs) Handles lstAllStudentData.SelectedIndexChanged
txtStudentName.Text = MyStudentArray(lstAllStudentData.SelectedIndex).StudentName
txtTest1.Text = MyStudentArray(lstAllStudentData.SelectedIndex).Test1
txtTest2.Text = MyStudentArray(lstAllStudentData.SelectedIndex).Test2
txtTest3.Text = MyStudentArray(lstAllStudentData.SelectedIndex).Test3
txtTest4.Text = MyStudentArray(lstAllStudentData.SelectedIndex).Test4
txtTest5.Text = MyStudentArray(lstAllStudentData.SelectedIndex).Test5
CalculateIndividual()
End Sub
Private Sub btnSearch_Click(sender As Object, e As EventArgs) Handles btnSearch.Click
Dim SearchField As String = txtSearch.Text
For StudentCounter = 0 To StudentCounter
If rdbStudent.Checked = True Then
If UCase(SearchField) = UCase(MyStudentArray(StudentCounter).StudentName) Then
lstAllStudentData.SelectedIndex = StudentCounter
Exit For
End If
End If
If rdbStudent.Checked = True Then
If UCase(SearchField) = UCase(MyStudentArray(StudentCounter).StudentName) Then
lstAllStudentData.SelectedIndex = StudentCounter
Exit For
End If
End If
Next
End Sub
Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
Dim StudentFile As New System.IO.StreamWriter("..\..\StudentDataFile.csv")
For StudentCounter = 0 To MyStudentArray.Length - 1
StudentFile.Write(MyStudentArray(StudentCounter).StudentName)
StudentFile.Write(",")
StudentFile.Write(MyStudentArray(StudentCounter).Test1)
StudentFile.Write(",")
StudentFile.Write(MyStudentArray(StudentCounter).Test3)
StudentFile.Write(",")
StudentFile.Write(MyStudentArray(StudentCounter).Test4)
StudentFile.Write(",")
StudentFile.Write(MyStudentArray(StudentCounter).Test4)
StudentFile.Write(",")
StudentFile.WriteLine(MyStudentArray(StudentCounter).Test5)
Next
StudentFile.Close()
End Sub
End Class