PictureBox doesn't display dynamically-generated Bitmap

Question

In a Visual Basic .NET Windows Forms application, I am creating Bitmap objects from raw EGA data and trying to display them in PictureBox controls. It can create the objects fine, as I determined by using the Immediate window to call GetPixel. SixteenColorBitmap is a class from a library I am using.

Function TileImage(Tile As SixteenColorBitmap) As Bitmap
    Dim b As New Bitmap(32, 32)
    For y = 1 To 16
        For x = 1 To 16
            Dim t = Tile.Color(x - 1, y - 1)
            Dim c As Color = Drawing.Color.FromArgb(RGB(t.Item1, t.Item2, t.Item3))
            b.SetPixel((x - 1) * 2, (y - 1) * 2, c)
            b.SetPixel((x - 1) * 2 + 1, (y - 1) * 2, c)
            b.SetPixel((x - 1) * 2, (y - 1) * 2 + 1, c)
            b.SetPixel((x - 1) * 2 + 1, (y - 1) * 2 + 1, c)
        Next
    Next
    Return b
End Function

On loading the EGA graphics, that is called for each tile and the result stored in a list. When the user selects a tile, it should pull the right tile ID out of that list and assign it to the Image property of that PictureBox, like this:

TileBackground.Image = BackgroundTiles(SelTile(0))

(TileBackground is a PictureBox, BackgroundTiles is the list of GDI+ bitmaps, and SelTile is the array of selected tiles.) When that code runs, as I am sure it is doing, the bitmap is assigned to the property, but it does not display on the form, even when I call Invalidate or Refresh.

Answer 1

Well, I did eventually get it working. As Jens suspected, something was wrong with the generated Bitmap, which was causing the PictureBox to freak out (silently) and not display it. The following code, for some unknown reason, works:

Function TileImage(Tile As SixteenColorBitmap) As Bitmap
    Dim b As New Bitmap(16, 16)
    For y = 1 To 16
        For x = 1 To 16
            Dim t = Tile.Color(x - 1, y - 1)
            Dim c As Color = Drawing.Color.FromArgb(255, t.Item1, t.Item2, t.Item3)
            b.SetPixel(x - 1, y - 1, c)
        Next
    Next
    Return b
End Function

Instead of manually doing the scale, I have the 32x32 control display my 16x16 image.