please help me fix a marshall.getlastwin32error error

[davidrobin]

I hope someone can help me out I am getting desperate.

The line

result = Win32.CreatePalette(memoryBlock)

in the module is returning an error 203.

Please help me to fix it.

I have a module (written by someone on another forum)

Imports System.Runtime.InteropServices
Imports System.Drawing
 
Module Module1
 
    Structure PALETTEENTRY
        Public peRed As Byte
        Public peGreen As Byte
        Public peBlue As Byte
        Public peFlags As Byte
    End Structure
 
    Structure LOGPALETTE
        Public palVersion As Short
        Public palNumEntries As Integer
    End Structure
 
    Public Class Win32
 
        <DllImport("Gdi32.dll", SetLastError:=True)> Shared Function _
            CreatePalette(ByVal ptr As IntPtr) As IntPtr
 
        End Function
 
        <DllImport("Gdi32.dll", SetLastError:=True)> Shared Function _
            GetNearestPaletteIndex(ByVal hpal As IntPtr, ByVal crColor As Int32) As Integer
 
        End Function
 
        <DllImport("Gdi32.dll")> Shared Function _
            DeleteObject(ByVal hObject As IntPtr) As Integer
 
        End Function
 
    End Class
 
    Sub Main()
 
        Dim hPalette As IntPtr
        Dim colors(256) As Color
        Dim i As Integer
 
        ' create grayscale palette as example
        For i = 0 To 255
            colors(i) = Color.FromArgb(0, i, i, i)
        Next
 
        hPalette = CreateWin32Palette(colors, 256)
 
        If Not hPalette.Equals(IntPtr.Zero) Then
            Console.WriteLine(GetPaletteIndex(hPalette, Color.FromArgb(0, 127, 127, 127)))
            Console.WriteLine(GetPaletteIndex(hPalette, Color.FromArgb(0, 200, 200, 200)))
            Console.WriteLine(GetPaletteIndex(hPalette, Color.FromArgb(0, 15, 100, 200)))
 
            ReleaseWin32Palette(hPalette)
        End If
 
    End Sub
 
    Public Function CreateWin32Palette(ByVal colors() As Color, ByVal nColors As Integer) As IntPtr
        Dim memoryBlock As IntPtr
        Dim ptr As IntPtr
        Dim address As Int32
        Dim nEntrySize As Integer
        Dim logPalette As LOGPALETTE
        Dim i As Integer
        Dim entries(256) As PALETTEENTRY
 
        ''''
        Dim result As IntPtr
        Dim nError As Integer
 
        If nColors < 1 Or nColors > 256 Then
            Return IntPtr.Zero
        End If
 
        nEntrySize = Marshal.SizeOf(entries(0))
 
        logPalette = New LOGPALETTE
        logPalette.palVersion = 768
        logPalette.palNumEntries = nColors
 
        memoryBlock = Marshal.AllocHGlobal( _
            nColors * nEntrySize + Marshal.SizeOf(logPalette))
 
        For i = 0 To nColors - 1
            entries(i).peRed = colors(i).R
            entries(i).peGreen = colors(i).G
            entries(i).peBlue = colors(i).B
            entries(i).peFlags = 0
        Next
 
        Marshal.StructureToPtr(logPalette, memoryBlock, False)
        address = memoryBlock.ToInt32() + Marshal.SizeOf(logPalette)
 
        For i = 0 To nColors - 1
            ptr = New IntPtr(address + i * nEntrySize)
            Marshal.StructureToPtr(entries(i), ptr, False)
        Next
 
        'Return Win32.CreatePalette(memoryBlock)
        result = Win32.CreatePalette(memoryBlock)
        nError = Marshal.GetLastWin32Error()
 
        Return result
 
    End Function
 
    Sub ReleaseWin32Palette(ByVal hPalette As IntPtr)
        Win32.DeleteObject(hPalette)
    End Sub
 
    Function GetPaletteIndex(ByVal hPalette As IntPtr, ByVal color As Color) As Integer
        Return Win32.GetNearestPaletteIndex(hPalette, color.ToArgb())
    End Function
 
End Module

This is my calling code

Dim intCount As Integer = 0
        Dim ct As Control
        For Each ct In gpbColours.Controls
            If TypeOf ct Is Label Then
                If ct.Name.Substring(0, ct.Name.IndexOf("_")).ToLower = "lblcolour" And ct.Text = "X" Then
                    intCount += 1
                End If
            End If
        Next
 
        Dim intElement As Integer = -1
        Dim colours() As Color
        ReDim colours(intCount - 1)
        Dim c As Control
        For Each c In gpbColours.Controls
            If TypeOf c Is Label Then
                If c.Name.Substring(0, c.Name.IndexOf("_")).ToLower = "lblcolour" And c.Text = "X" Then
                    intElement += 1
                    colours(intElement) = c.BackColor
                End If
            End If
        Next
 
        'Dim i As Integer
        'For i = 0 To intCount - 1
        '    Debug.WriteLine(colours(i).R.ToString + ", " + colours(i).G.ToString + ", " + colours(i).B.ToString)
        'Next
 
        Dim hPalette As IntPtr
 
        hPalette = CreateWin32Palette(colours, intCount)
 
        If Not hPalette.Equals(IntPtr.Zero) Then
 
            Console.WriteLine(GetPaletteIndex(hPalette, Color.FromArgb(0, 127, 127, 127)))
            Console.WriteLine(GetPaletteIndex(hPalette, Color.FromArgb(0, 200, 200, 200)))
            Console.WriteLine(GetPaletteIndex(hPalette, Color.FromArgb(0, 15, 100, 200)))
 
            ReleaseWin32Palette(hPalette)
        End If