Adding records (Row/ Column) to DataGridView; Collection already belongs to a DataGridView control VB.NET - vb.net

Question

I'm looking for some help with an issue I am having.
I have multiple text files, in a folder. The folder can have an "unlimited" amount of text files in it, although typically 2-150 files
http://gyazo.com/5f314d1ca374abf9f813914609dd931d (images for this + below, can't embed due to lack of reputation)
Each file then contains an "unlimited" (although typically 0-20 lines) amount of data inside it. Line 1 being the "test number" and line 2 being the "test result" - as seen in the image above
My Data Grid View has 3 columns in it (Username, test number, test result) - as seen in the image above
When running my code below; first record being added to the Data Grid View works perfectly, but the second (or any record after the first) the error occurs:
http://gyazo.com/0d492b97d918853e62c55ee314f3f181 (image) or error message:
"System.InvalidOperationException: Collection already belongs to a
DataGridView control. This operation is no longer valid. at
System.Windows.Forms.DataGridViewCellCollection.Add(DataGridViewCelldataGridViewCell)
at SpellingBee.TeacherMultiResults.TeacherMultiResults_Load(Object
sender, EventArgs e)"
This error occurs on the DGVRow.Cells.Add(DGVCell) 'add cell to row
One thing I don't want to do is change any of my text file/ folder structures, even though I'm aware that it is currently inefficient storage.
How can I fix this error? I'm using VB.net (Visual Studios 2013)
If you need any more information, please just ask
Many thanks.
Imports System.Windows.Forms
Imports System.IO
Public Class TeacherMultiResults
Dim AmountOfFiles
Dim LineCount As Integer = 0
Dim FileName As IO.FileInfo
Dim DGVRow As New DataGridViewRow
Dim DGVCell As DataGridViewCell
Dim Username As String = ""
Dim TestNumber As Integer = 0
Dim TestResult As Integer = 0
Private Sub TeacherMultiResults_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim directory As New IO.DirectoryInfo(LoadForm.CurrentDirectory & "\UserResults\") 'selects directory
Dim FileNames As IO.FileInfo() = directory.GetFiles()
Dim Files As IO.FileInfo
For Each Files In FileNames 'list the names of all files in the specified directory
Username = Files.ToString
Username = (Username.Substring(0, Username.Length - 4)) 'removes the .txt from the name
Try
LineCount = File.ReadAllLines(LoadForm.CurrentDirectory & "\UserResults\" & Username & ".txt").Length 'amount of lines in file
If LineCount > 1 Then
Dim Information As New System.IO.StreamReader(LoadForm.CurrentDirectory & "\UserResults\" & Username & ".txt") 'opens file
LineCount = LineCount / 2 'halfs line count
For i = 0 To LineCount - 1
TestNumber = Information.ReadLine() 'reads line to variable
TestResult = Information.ReadLine() 'reads line to variable
i = i + 1 'adds one to i
DGVCell = New DataGridViewTextBoxCell 'create a new DGV text box cell
DGVCell.Value = Username 'add value to DGV text box cell
DGVRow.Cells.Add(DGVCell) 'add cell to row
DGVCell = New DataGridViewTextBoxCell 'create a new DGV text box cell
DGVCell.Value = TestNumber 'add value to DGV text box cell
DGVRow.Cells.Add(DGVCell) 'add cell to row
DGVCell = New DataGridViewTextBoxCell 'create a new DGV text box cell
DGVCell.Value = TestResult 'add value to DGV text box cell
DGVRow.Cells.Add(DGVCell) 'add cell to row
DGV_MultiResults.Rows.Add(DGVRow) 'add row to DGV
Next
Information.Close() 'Close read
End If
Catch ex As Exception 'if file won't read
MsgBox(ex.ToString) 'show error
Exit Try
End Try 'end of try
Next 'end of files
End Sub
I hope that somebody can help me with this issue, I understand it's fairly simple to fix most probably although I can't seem to find a solution to the error!
Many thanks, Toby.

Answer 1

When working with a DataGridView, it is generally easier to just build an object list and then bind it to the DGV using the built-in data binding features.
For your example, it would look like this:
' Read the files, build objects as you go and add them to a list
Dim lst = New List(Of TeacherMultiResults)
' Replace this part with your file reading code...
Dim t1 = New TeacherMultiResults With {.Username = "Bob", .TestNumber = 1, .TestResult = 75}
lst.Add(t1)
Dim t2 = New TeacherMultiResults With {.Username = "Rick", .TestNumber = 1, .TestResult = 85}
lst.Add(t2)
Dim t3 = New TeacherMultiResults With {.Username = "Zoe", .TestNumber = 1, .TestResult = 95}
lst.Add(t3)
' Bind the list to the DataGridView
Dim bindList = New BindingList(Of TeacherMultiResults)(lst)
Dim bindSrc = New BindingSource
bindSrc.DataSource = bindList
grid.DataSource = bindSrc
Your grid should display each item of your list.