VB.Net GIF Transparency

Public Shared Function GetTransparentGif( _
        ByVal Image As Bitmap, _
        ByVal TransparentColor As Color _
    ) As Image
        Dim w As Integer = Image.Width
        Dim h As Integer = Image.Height
        Dim bmp As Bitmap = New Bitmap(w, h, PixelFormat.Format8bppIndexed)
        Dim originalPalette As ColorPalette = Image.Palette
        Dim palette As ColorPalette = bmp.Palette
        Dim lastentry, k As Integer
        
        ' Copy all of the entries from the old palette, removing any
        ' transparency.
        For i As Integer = 0 To originalPalette.Entries.Length - 1
            Dim baseColor As Color = originalPalette.Entries(i)
            Dim alpha As Integer = CInt(IIf(baseColor.Equals(TransparentColor), 0, 255))
            ' Set the palette entry, setting the transparent color based on
            ' whether it is the same as the transparent color argument.
            palette.Entries(i) = Color.FromArgb(255, baseColor)'make all entries non transparent
            If alpha = 0 Then
                k += 1
                lastentry = i 'in a VB Net-palette the fitting entry is allways the last one, but only if the gif is created by "pic.save(filename,imaging.imageformat.gif)" from a normal bitmap! If you set more than one entry as transparent, the gif will not work when you save it!
            End If
        Next
        
        Dim basecolor1 As Color = originalPalette.Entries(lastentry) 'Set only the last fitting entry as transparent!
        palette.Entries(lastentry) = Color.FromArgb(0, basecolor1)
        
        ' Re-insert the palette.
        bmp.Palette = palette
        
        ' Transfer the bitmap data from the source image to the new image.
        TransferBytes(Image, bmp)
        
        ' Return the new image.
        Return bmp
    End Function