The case of the Disappearing and Reappearing Lines: Dervied DataGridColumnStyle

[tom_hotspur]

I've written a dervied DataGridColumnStyle class (inherits from DataGridTextBoxColumn) and overridden the Paint member so that i can specifiy which side of the column a vertical line is drawn.

Like so:

Public Sub New(ByVal left As Boolean, ByVal right As Boolean)
        'constructor
        drawLeft = left
        drawRight = right
    End Sub
 
  '**other subs that REQUIRE to be overridden
  '** are included in the class but they don't do much so
  '** i've not bothered to include them here
 
   Protected Overloads Overrides Sub Paint(ByVal g As _
   System.Drawing.Graphics, ByVal bounds As _
   System.Drawing.Rectangle, ByVal source As _
   System.Windows.Forms.CurrencyManager, ByVal rowNum As _
   Integer)
 
        Paint(g, bounds, source, rowNum)
 
    End Sub
 
    Protected Overloads Overrides Sub Paint(ByVal g As _
    System.Drawing.Graphics, ByVal bounds As _
    System.Drawing.Rectangle, ByVal source As _
    System.Windows.Forms.CurrencyManager, ByVal rowNum As _
    Integer, ByVal alignToRight As Boolean)
 
        Paint(g, bounds, source, rowNum, alignToRight)
 
    End Sub
 
    Protected Overloads Overrides Sub Paint(ByVal g As _
    System.Drawing.Graphics, ByVal bounds As _
    System.Drawing.Rectangle, ByVal source As _
    System.Windows.Forms.CurrencyManager, ByVal rowNum As _
    Integer, ByVal BackBrush As Brush, ByVal ForeBrush As Brush, _
    ByVal AlignToRight As Boolean)
        'pen
        Dim p As Pen = New Pen(Color.Black)
 
        'font
        Dim font As Font = New System.Drawing.Font("Arial", 9)
 
        'string
        Dim str As String
 
        'coordinates used for drawing lines
        '(origin points)
        Dim x1 As Single
        Dim y1 As Single
 
        'set start coordinates
        x1 = bounds.Location.X
        y1 = bounds.Location.Y
 
        g.FillRectangle(BackBrush, bounds)
 
        'draw the horizontal line
        g.DrawLine(p, x1, y1, x1 + bounds.Width, y1)
 
        'draw vertical line on left if flag set
        If drawLeft = True Then
            g.DrawLine(p, x1, y1, x1, y1 + bounds.Height)
        End If
 
        'draw vertical line on right if flag set
        If drawRight = True Then
            g.DrawLine(p, x1 + bounds.Width, y1, x1 + bounds.Width, y1 + bounds.Height)
        End If
 
        str = GetColumnValueATrow(source, rowNum)
 
        'draw the text
        g.DrawString(str, font, Brushes.Black, bounds.X, bounds.Y)
 
    End Sub

Then when i use the columnstyle with my tablestyle and datagrid i find that it does not draw the vertical lines. But if i remove the 'if' statement for the left vertical line it draws the line.

Also if remove the

g.FillRectangle(BackBrush, bounds)

the vertical lines are visible BUT obviously every time i scroll down it overwrites what was there previously and makes a scribbled mess.


I Suppose a possible solution is to create two classes, one for both sides. But surely this can be achieved with one class?

Any ideas where i'm going wrong?