Custom DataGridViewCell flickering when painted.

vb.net Code:

Imports System.Drawing
Imports System.Windows.Forms.VisualStyles
 
Public Class CheckBoxColumn
    Inherits Windows.Forms.DataGridViewCheckBoxColumn
 
    Sub New()
        Me.CellTemplate = New CheckBoxCell
    End Sub
End Class
 
Public Class TextBoxColumn
    Inherits Windows.Forms.DataGridViewTextBoxColumn
 
    Sub New()
        Me.CellTemplate = New TextBoxCell
    End Sub
End Class
 
Public Class TextBoxCell
    Inherits Windows.Forms.DataGridViewTextBoxCell
 
    Public Overrides Function AdjustCellBorderStyle( _
            ByVal dataGridViewAdvancedBorderStyleInput As Windows.Forms.DataGridViewAdvancedBorderStyle, _
            ByVal dataGridViewAdvancedBorderStylePlaceHolder As Windows.Forms.DataGridViewAdvancedBorderStyle, _
            ByVal singleVerticalBorderAdded As Boolean, _
            ByVal singleHorizontalBorderAdded As Boolean, _
            ByVal firstVisibleColumn As Boolean, _
            ByVal firstVisibleRow As Boolean) As Windows.Forms.DataGridViewAdvancedBorderStyle
 
        ' Customize the top border of cells in the first row and the  
        ' right border of cells in the first column. Use the input style  
        ' for all other borders. 
 
        With dataGridViewAdvancedBorderStylePlaceHolder
 
            If firstVisibleColumn Then
                .Left = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
            Else
                .Left = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
            End If
 
            If firstVisibleRow Then
                .Top = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
            Else
                .Top = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
            End If
 
            If Me.ColumnIndex = DataGridView.DisplayedColumnCount(False) - 1 Then
                .Right = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
            Else
                .Right = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
            End If
 
            If RowIndex = DataGridView.FirstDisplayedCell.RowIndex + DataGridView.DisplayedRowCount(False) - 1 Then
                .Bottom = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
            Else
                .Bottom = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
            End If
 
            ' .Right = dataGridViewAdvancedBorderStyleInput.Right
            ' .Bottom = dataGridViewAdvancedBorderStyleInput.Bottom
        End With
 
        Return dataGridViewAdvancedBorderStylePlaceHolder
    End Function
 
    'Protected Overrides Sub Paint(graphics As Drawing.Graphics, clipBounds As Drawing.Rectangle, cellBounds As Drawing.Rectangle, rowIndex As Integer, elementState As Windows.Forms.DataGridViewElementStates, value As Object, formattedValue As Object, errorText As String, cellStyle As Windows.Forms.DataGridViewCellStyle, advancedBorderStyle As Windows.Forms.DataGridViewAdvancedBorderStyle, paintParts As Windows.Forms.DataGridViewPaintParts)
    '    MyBase.Paint(graphics, clipBounds, cellBounds, rowIndex, elementState, value, formattedValue, errorText, cellStyle, advancedBorderStyle, paintParts)
 
    '    ' Draw Background
    '    If (paintParts And Windows.Forms.DataGridViewPaintParts.SelectionBackground) = Windows.Forms.DataGridViewPaintParts.SelectionBackground Then
    '        If rowIndex = DataGridView.CurrentRow.Index AndAlso DataGridView.SelectionMode = Windows.Forms.DataGridViewSelectionMode.FullRowSelect Then
    '            Using cellBackground As New SolidBrush(cellStyle.SelectionBackColor)
    '                graphics.FillRectangle(cellBackground, cellBounds)
    '            End Using
    '        Else
    '            Using cellBackground As New SolidBrush(cellStyle.BackColor)
    '                graphics.FillRectangle(cellBackground, cellBounds)
    '            End Using
    '        End If
    '    End If
 
    '    ' Draw Borders
    '    If (paintParts And Windows.Forms.DataGridViewPaintParts.Border) = Windows.Forms.DataGridViewPaintParts.Border Then
    '        With advancedBorderStyle
    '            ' .All = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
 
    '            'If rowIndex = DataGridView.FirstDisplayedCell.RowIndex Then
    '            '    .Top = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
    '            'End If
 
    '            If Me.ColumnIndex = DataGridView.FirstDisplayedCell.ColumnIndex Then
    '                .Left = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
    '            Else
    '                .Left = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
    '            End If
 
    '            If Me.ColumnIndex = DataGridView.DisplayedColumnCount(False) - 1 Then
    '                .Right = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
    '            Else
    '                .Right = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
    '            End If
 
    '            If cellBounds.X + cellBounds.Width = clipBounds.Width Then
 
    '            End If
 
    '            If rowIndex = DataGridView.FirstDisplayedCell.RowIndex + DataGridView.DisplayedRowCount(False) - 1 Then
    '                .Bottom = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
    '            Else
    '                .Bottom = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
    '            End If
    '        End With
 
    '        PaintBorder(graphics, clipBounds, cellBounds, cellStyle, advancedBorderStyle)
    '    End If
 
    'End Sub
 
End Class
 
Public Class CheckBoxCell
 
    'Public Overrides Function AdjustCellBorderStyle( _
    '        ByVal dataGridViewAdvancedBorderStyleInput As Windows.Forms.DataGridViewAdvancedBorderStyle, _
    '        ByVal dataGridViewAdvancedBorderStylePlaceHolder As Windows.Forms.DataGridViewAdvancedBorderStyle, _
    '        ByVal singleVerticalBorderAdded As Boolean, _
    '        ByVal singleHorizontalBorderAdded As Boolean, _
    '        ByVal firstVisibleColumn As Boolean, _
    '        ByVal firstVisibleRow As Boolean) As Windows.Forms.DataGridViewAdvancedBorderStyle
 
    '    ' Customize the top border of cells in the first row and the  
    '    ' right border of cells in the first column. Use the input style  
    '    ' for all other borders. 
    '    If firstVisibleColumn Then
    '        dataGridViewAdvancedBorderStylePlaceHolder.Left = _
    '           Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
    '    Else
    '        dataGridViewAdvancedBorderStylePlaceHolder.Left = dataGridViewAdvancedBorderStyleInput.Left
    '    End If
 
    '    If firstVisibleRow Then
    '        dataGridViewAdvancedBorderStylePlaceHolder.Top = _
    '           Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
    '    Else
    '        dataGridViewAdvancedBorderStylePlaceHolder.Top = dataGridViewAdvancedBorderStyleInput.Top
    '    End If
 
    '    With dataGridViewAdvancedBorderStylePlaceHolder
 
    '        .Right = dataGridViewAdvancedBorderStyleInput.Right
    '        .Bottom = dataGridViewAdvancedBorderStyleInput.Bottom
    '    End With
 
    '    Return dataGridViewAdvancedBorderStylePlaceHolder
    'End Function
 
    Protected Overrides Function GetFormattedValue(value As Object, rowIndex As Integer, ByRef cellStyle As Windows.Forms.DataGridViewCellStyle, valueTypeConverter As ComponentModel.TypeConverter, formattedValueTypeConverter As ComponentModel.TypeConverter, context As Windows.Forms.DataGridViewDataErrorContexts) As Object
        Return If(Me.Value Is Nothing OrElse Not Convert.ToBoolean(Me.Value), False, Convert.ToBoolean(Me.Value))
    End Function
 
    Protected Overrides Sub Paint(graphics As Drawing.Graphics, clipBounds As Drawing.Rectangle, cellBounds As Drawing.Rectangle, rowIndex As Integer, elementState As Windows.Forms.DataGridViewElementStates, value As Object, formattedValue As Object, errorText As String, cellStyle As Windows.Forms.DataGridViewCellStyle, advancedBorderStyle As Windows.Forms.DataGridViewAdvancedBorderStyle, paintParts As Windows.Forms.DataGridViewPaintParts)
        MyBase.Paint(graphics, clipBounds, cellBounds, rowIndex, elementState, value, formattedValue, errorText, cellStyle, advancedBorderStyle, paintParts)
 
        Dim x As Int32 = CInt(cellBounds.Width / 2 - 8)
        Dim y As Int32 = CInt(cellBounds.Height / 2 - 8)
 
        With graphics
 
            ' Draw Background
            If (paintParts And Windows.Forms.DataGridViewPaintParts.SelectionBackground) = Windows.Forms.DataGridViewPaintParts.SelectionBackground Then
                If rowIndex = DataGridView.CurrentRow.Index AndAlso DataGridView.SelectionMode = Windows.Forms.DataGridViewSelectionMode.FullRowSelect Then
                    Using cellBackground As New SolidBrush(cellStyle.SelectionBackColor)
                        graphics.FillRectangle(cellBackground, cellBounds)
                    End Using
                Else
                    Using cellBackground As New SolidBrush(cellStyle.BackColor)
                        graphics.FillRectangle(cellBackground, cellBounds)
                    End Using
                End If
            End If
 
            ' Draw Borders
            If (paintParts And Windows.Forms.DataGridViewPaintParts.Border) = Windows.Forms.DataGridViewPaintParts.Border Then
                With advancedBorderStyle
                    ' .All = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
 
                    'If rowIndex = DataGridView.FirstDisplayedCell.RowIndex Then
                    '    .Top = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
                    'End If
 
                    If Me.ColumnIndex = DataGridView.FirstDisplayedCell.ColumnIndex Then
                        .Left = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
                    Else
                        .Left = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
                    End If
 
                    If Me.ColumnIndex = DataGridView.DisplayedColumnCount(False) - 1 Then
                        .Right = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
                    Else
                        .Right = Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
                    End If
 
                    If cellBounds.X + cellBounds.Width = clipBounds.Width Then
 
                    End If
 
                    'If rowIndex = DataGridView.FirstDisplayedCell.RowIndex + DataGridView.DisplayedRowCount(False) - 1 Then
                    '    .Bottom = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
                    'End If
 
                    If cellBounds.Y + 1 <> clipBounds.Height Then
 
                    End If
                End With
 
                PaintBorder(graphics, clipBounds, cellBounds, cellStyle, advancedBorderStyle)
            End If
 
            ' CheckBox 
            Using cellBackground As New SolidBrush(cellStyle.BackColor)
                graphics.FillRectangle(cellBackground, x + cellBounds.X, y + cellBounds.Y, 15, 15)
            End Using
 
            checkBrush.Color = Me.DataGridView.RowsDefaultCellStyle.ForeColor
            checkPen.Color = Me.DataGridView.GridColor
 
            .DrawRectangle(checkPen, x + cellBounds.X, y + cellBounds.Y, 15, 15)
 
            ' Check State
            If CBool(EditedFormattedValue) = True Then
                .DrawString("✓", checkFont, checkBrush, New Point(x + cellBounds.X, y + cellBounds.Y))
            End If
 
        End With
 
    End Sub
 
    Private checkFont As New Font("Segoe UI", 9, FontStyle.Bold)
    Private checkBrush As New SolidBrush(Color.Black)
    Private checkPen As New Pen(Color.Black, 1)
 
    Sub New()
 
        ' This call is required by the designer.
        InitializeComponent()
 
        ' Add any initialization after the InitializeComponent() call.
 
    End Sub
 
 
 
End Class
 
Public Class DataGridViewCustomRow
    Inherits Windows.Forms.DataGridViewRow
 
    Public Overrides Function AdjustRowHeaderBorderStyle( _
        ByVal dataGridViewAdvancedBorderStyleInput As Windows.Forms.DataGridViewAdvancedBorderStyle, _
        ByVal dataGridViewAdvancedBorderStylePlaceHolder As Windows.Forms.DataGridViewAdvancedBorderStyle, _
        ByVal singleVerticalBorderAdded As Boolean, _
        ByVal singleHorizontalBorderAdded As Boolean, _
        ByVal isFirstDisplayedRow As Boolean, _
        ByVal isLastDisplayedRow As Boolean) As Windows.Forms.DataGridViewAdvancedBorderStyle
 
        ' Customize the top border of the first row header and the 
        ' right border of all the row headers. Use the input style for  
        ' all other borders. 
        If isFirstDisplayedRow Then
            dataGridViewAdvancedBorderStylePlaceHolder.Top = _
                Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
        Else
            dataGridViewAdvancedBorderStylePlaceHolder.Top = _
                Windows.Forms.DataGridViewAdvancedCellBorderStyle.None
        End If
 
        With dataGridViewAdvancedBorderStylePlaceHolder
            .Right = Windows.Forms.DataGridViewAdvancedCellBorderStyle.Single
            .Left = dataGridViewAdvancedBorderStyleInput.Left
            .Bottom = dataGridViewAdvancedBorderStyleInput.Bottom
        End With
 
        Return dataGridViewAdvancedBorderStylePlaceHolder
    End Function
End Class

This is the code I have been fiddling with. The DataGridView I am using is double-buffered, if that matters. Maybe I am going about it all wrong.

The problem:
The borders that get drawn on the bottom of the last visible row flicker when I scroll the DataGridView. None of the other borders flicker.

What I want:
I want to be able to specify which borders get drawn, without flickering.

What I have tried:
Different versions of the above code. I have also placed a Refresh command in the scroll event of the DataGridView. This was needed so that all the cells actually get redrawn.

Should I be using the CellPainting event? Maybe some other method?