Public Class BorderCell
    Inherits DataGridViewTextBoxCell

    Protected Overrides Sub Paint(graphics As Graphics, clipBounds As Rectangle, cellBounds As Rectangle, rowIndex As Integer, cellState As DataGridViewElementStates, value As Object, formattedValue As Object, errorText As String, cellStyle As DataGridViewCellStyle, advancedBorderStyle As DataGridViewAdvancedBorderStyle, paintParts As DataGridViewPaintParts)
        MyBase.Paint(graphics, clipBounds, cellBounds, rowIndex, cellState, value, formattedValue, errorText, cellStyle, advancedBorderStyle, paintParts)

        'Ignore if thickness is too small.
        if _borderThickness = 0 Then Return

        'Specify size and position of the border.
        Dim borderRect = New Rectangle(cellBounds.X + 1, cellBounds.Y + 1, cellBounds.Width - 4, cellBounds.Height - 4)
        'Draw border with specified thickness.
        graphics.DrawRectangle(New Pen(BorderColor, _borderThickness), borderRect)

        'Create spacing between text and border.
        Me.Style.Padding = New Padding(1)
    End Sub

    Private _borderThickness As Integer = 1
    Property BorderThickness As Integer
        Set(thickness As Integer)
            If thickness < 0 Then Throw New Exception($"Border thickness of {Me.GetType().Name} can't be smaller than 0.")
            _borderThickness = thickness
        End Set
        Get
            Return _borderThickness
        End Get
    End Property

    Public Property BorderColor As Color = Drawing.Color.Black
End Class