Mick Doherty's .net Miscellaneous Tips.

Restrict the Minimum and Maximum Size of a UserControl.

The Following Code is based on an example originally posted by Jacob Grass.

			VB Code
			
			'This line must be inserted before any Class or NameSpace Code.
Imports System.Runtime.InteropServices

<StructLayoutAttribute(LayoutKind.Sequential)> _
Structure WM_PosChanging
    Dim hWnd, hWndInsertAfter, X, Y, cX, cY, Flags As Integer
End Structure

Protected Const WM_WINDOWPOSCHANGING As Integer = &H46
Protected MaxSize As Size = New Size(64, 64)
Protected MinSize As Size = New Size(16, 16)

Protected Overrides Sub WndProc(ByRef m As Message)
    If m.Msg = WM_WINDOWPOSCHANGING Then
        Dim lParam As WM_PosChanging = _
        CType(m.GetLParam(GetType(WM_PosChanging)), WM_PosChanging)
        Static Pos As Point = New Point(lParam.X, lParam.Y)

        If lParam.cX >= MaxSize.Width Then
            If lParam.cX > MaxSize.Width Then lParam.X = Pos.X
            lParam.cX = MaxSize.Width
        ElseIf lParam.cX <= MinSize.Width Then
            If lParam.cX < MinSize.Width Then lParam.X = Pos.X
            lParam.cX = MinSize.Width
        End If

        If lParam.cY >= MaxSize.Height Then
            If lParam.cY > MaxSize.Height Then lParam.Y = Pos.Y
            lParam.cY = MaxSize.Height
        ElseIf lParam.cY <= MinSize.Height Then
            If lParam.cY < MinSize.Height Then lParam.Y = Pos.Y
            lParam.cY = MinSize.Height
        End If

        Pos = New Point(lParam.X, lParam.Y)
        Marshal.StructureToPtr(lParam, m.LParam, True)
    End If

    MyBase.WndProc(m)
End Sub

Protected Overrides ReadOnly Property DefaultSize() As System.Drawing.Size
    Get
        Return New Size(32, 32)
    End Get
End Property      
			
C# Code
			
			//This line must be inserted before any Class or NameSpace Code.
using System.Runtime.InteropServices;

[StructLayoutAttribute(LayoutKind.Sequential)]
struct WM_PosChanging
{
    public int hWnd;
    public int hWndInsertAfter;
    public int X;
    public int Y;
    public int cX;
    public int cY;
    public int Flags;
}

protected const int WM_WINDOWPOSCHANGING = 0x46;

protected Size MinSize = new Size(16, 16);
protected Size MaxSize = new Size(64, 64);
Point Pos;

protected override void WndProc(ref Message m)
{
    if (m.Msg == WM_WINDOWPOSCHANGING)
    {
        WM_PosChanging lParam = ((WM_PosChanging)m.GetLParam(typeof(WM_PosChanging)));
        //I was surprised to find that there is no C# equivelant of VB's Static Variable.
        //static in C# is something completely different.
        if (Pos.IsEmpty)Pos = new Point(lParam.X, lParam.Y);
        if (lParam.cX <= MinSize.Width)
        {
            if (lParam.cX < MinSize.Width) lParam.X = Pos.X;
            lParam.cX = MinSize.Width;
        }
        else if (lParam.cX >= MaxSize.Width)
        {
            if (lParam.cX > MaxSize.Width) lParam.X = Pos.X;
            lParam.cX = MaxSize.Width;
        }

        if (lParam.cY <= MinSize.Height)
        {
            if (lParam.cY < MinSize.Height) lParam.Y = Pos.Y;
            lParam.cY = MinSize.Height;
        }
        else if (lParam.cY >= MaxSize.Height)
        {
            if (lParam.cY > MaxSize.Height) lParam.Y = Pos.Y;
            lParam.cY = MaxSize.Height;
        }

        Pos = new Point(lParam.X, lParam.Y);
        Marshal.StructureToPtr(lParam, m.LParam, true);
    }
    base.WndProc (ref m);
}

protected override Size DefaultSize
{
    get
    {
        return new Size(32,32);
    }
}
			
			

			

Get Alpha Bitmap from 32 bit Icon.

Get rid of those ugly shadows.

			VB Code
			
			Imports System.Runtime.InteropServices
Imports System.Drawing.Imaging

#Region " IconInfo"

    <DllImport("gdi32.dll", SetLastError:=True)> _
    Private Shared Function DeleteObject(ByVal hObject As IntPtr) As Boolean
    End Function

    <DllImport("user32.dll", CallingConvention:=CallingConvention.Cdecl)> _
    Private Shared Function GetIconInfo(ByVal hIcon As IntPtr, ByRef piconinfo As ICONINFO) As Boolean
    End Function

    Private Structure ICONINFO
        Dim fIcon As Boolean
        Dim xHotspot As Integer
        Dim yHotspot As Integer
        Dim hbmMask As IntPtr
        Dim hbmColor As IntPtr
    End Structure

#End Region

Private Function IconToAlphaBitmap(ByVal ico As Icon) As Bitmap

    Dim ii As New ICONINFO

    GetIconInfo(ico.Handle, ii)

    Dim bmp As Bitmap = Bitmap.FromHbitmap(ii.hbmColor)
    DeleteObject(ii.hbmColor)
    DeleteObject(ii.hbmMask)

    If Bitmap.GetPixelFormatSize(bmp.PixelFormat) < 32 Then
        Return ico.ToBitmap
    End If

    Dim bmData As Imaging.BitmapData
    Dim bmBounds As New Rectangle(0, 0, bmp.Width, bmp.Height)

    bmData = bmp.LockBits(bmBounds, _
                ImageLockMode.ReadOnly, _
                bmp.PixelFormat)

    Dim dstBitmap As New Bitmap(bmData.Width, _
                bmData.Height, _
                bmData.Stride, _
                PixelFormat.Format32bppArgb, _
                bmData.Scan0)

    Dim x, y As Integer
    Dim IsAlphaBitmap As Boolean = False

    For y = 0 To bmData.Height - 1
        For x = 0 To bmData.Width - 1
            Dim PixelColor As Color
            PixelColor = Color.FromArgb(Marshal.ReadInt32(bmData.Scan0, (bmData.Stride * y) + (4 * x)))
            If PixelColor.A > 0 And PixelColor.A < 255 Then
                IsAlphaBitmap = True
                Exit For
            End If
        Next
        If IsAlphaBitmap Then Exit For
    Next

    bmp.UnlockBits(bmData)

    If IsAlphaBitmap Then
        Return New Bitmap(dstBitmap)
    Else
        Return New Bitmap(ico.ToBitmap)
    End If

End Function      
			
C# Code
			
			using System.Runtime.InteropServices;
using System.Drawing.Imaging;

[DllImport("gdi32.dll", SetLastError=true)]
static extern bool DeleteObject(IntPtr hObject);

[DllImport("user32.dll")]
static extern bool GetIconInfo(IntPtr hIcon, out ICONINFO piconinfo);

public struct ICONINFO
{
    public bool fIcon;
    public int xHotspot;
    public int yHotspot;
    public IntPtr hbmMask;
    public IntPtr hbmColor;
}


private Bitmap IconToAlphaBitmap(Icon ico)
{
    ICONINFO ii = new ICONINFO();
    GetIconInfo(ico.Handle, out ii);
    Bitmap bmp = Bitmap.FromHbitmap(ii.hbmColor);
    DeleteObject(ii.hbmColor);
    DeleteObject(ii.hbmMask);

    if (Bitmap.GetPixelFormatSize(bmp.PixelFormat) < 32)
        return ico.ToBitmap();

    BitmapData bmData;
    Rectangle bmBounds = new Rectangle(0,0,bmp.Width,bmp.Height);

    bmData = bmp.LockBits(bmBounds,ImageLockMode.ReadOnly, bmp.PixelFormat);
            
    Bitmap dstBitmap=new Bitmap(bmData.Width, bmData.Height, bmData.Stride, PixelFormat.Format32bppArgb, bmData.Scan0);

    bool IsAlphaBitmap = false;

    for (int y=0; y <= bmData.Height-1; y++)
    {
        for (int x=0; x <= bmData.Width-1; x++)
        {
            Color PixelColor = Color.FromArgb(Marshal.ReadInt32(bmData.Scan0, (bmData.Stride * y) + (4 * x)));
            if (PixelColor.A > 0 & PixelColor.A < 255)
            {
                IsAlphaBitmap = true;
                break;
            }
        }
        if (IsAlphaBitmap) break;
    }

    bmp.UnlockBits(bmData);

    if (IsAlphaBitmap==true)
        return new Bitmap(dstBitmap);
    else
        return new Bitmap(ico.ToBitmap());
          
}
			
			

			

Save the Image currently displayed in a PictureBox.

In the good old days (pre dotnet) a Picturebox had an Image property and a Picture property. The Picture property was the equivelant of today's Image property, whilst the Image property was the Image actually displayed in the Picturebox.
If you draw to a Picturebox in it's paint method then that drawing will persist in the picturebox, but if you try to save the resultant image, you will find that you won't save any of the extra drawing done in paint.
The following code will allow you to save the Image with all extra painting.

			VB Code
			
			Sub SaveImage(ByVal pb As PictureBox, ByVal sFile As String)
    Dim bmp As New Bitmap(pb.Width, pb.Height)
    Dim g As Graphics = Graphics.FromImage(bmp)
    Dim pe As New PaintEventArgs(g, New Rectangle(Point.Empty, bmp.Size))
    Me.InvokePaint(pb, pe)
    Dim fmt As Imaging.ImageFormat
    Dim lFile As String = sFile.ToLower
    If lFile.EndsWith(".emf") Then
        fmt = Imaging.ImageFormat.Emf
    ElseIf lFile.EndsWith(".exif") Then
        fmt = Imaging.ImageFormat.Exif
    ElseIf lFile.EndsWith(".gif") Then
        fmt = Imaging.ImageFormat.Gif
    ElseIf lFile.EndsWith(".jpg") OrElse lFile.EndsWith(".jpeg") Then
        fmt = Imaging.ImageFormat.Jpeg
    ElseIf lFile.EndsWith(".png") Then
        fmt = Imaging.ImageFormat.Png
    ElseIf lFile.EndsWith(".tiff") OrElse lFile.EndsWith(".tif") Then
        fmt = Imaging.ImageFormat.Tiff
    ElseIf lFile.EndsWith(".wmf") Then
        fmt = Imaging.ImageFormat.Wmf
    Else
        fmt = Imaging.ImageFormat.Bmp
    End If
    bmp.Save(sFile, fmt)
    g.Dispose()
    bmp.Dispose()
    pe.Dispose()
End Sub      
			
C# Code
			
			void SaveImage(PictureBox pb, String sFile)
{
    Bitmap bmp = new Bitmap(pb.Width, pb.Height);
    Graphics g = Graphics.FromImage(bmp);
    PaintEventArgs pe = new PaintEventArgs(g, new Rectangle(Point.Empty, bmp.Size));
    this.InvokePaint(pb, pe);
    System.Drawing.Imaging.ImageFormat fmt;
    String lFile = sFile.ToLower();
    if (lFile.EndsWith(".emf"))
        fmt = System.Drawing.Imaging.ImageFormat.Emf;
    else if (lFile.EndsWith(".exif"))
        fmt = System.Drawing.Imaging.ImageFormat.Exif;
    else if (lFile.EndsWith(".gif"))
        fmt = System.Drawing.Imaging.ImageFormat.Gif;
    else if (lFile.EndsWith(".jpg") || lFile.EndsWith(".jpeg"))
        fmt = System.Drawing.Imaging.ImageFormat.Jpeg;
    else if (lFile.EndsWith(".png"))
        fmt = System.Drawing.Imaging.ImageFormat.Png;
    else if (lFile.EndsWith(".tiff") || lFile.EndsWith(".tif"))
        fmt = System.Drawing.Imaging.ImageFormat.Tiff;
    else if (lFile.EndsWith(".wmf"))
        fmt = System.Drawing.Imaging.ImageFormat.Wmf;
    else
        fmt = System.Drawing.Imaging.ImageFormat.Bmp;
            
    bmp.Save(sFile, fmt);
    g.Dispose();
    bmp.Dispose();
    pe.Dispose();
}
			
			

			

Draw 32 bit images from an Imagelist.

Useful for controls that don't have an imagelist property or for painting in your own custom control.
Note that pngs added to an imagelist will draw alpha with a blue tint so, if possible, add icons to the imagelist.
Also note that 32 bit images should be loaded into the imagelist at runtime or the imagelist will 'Flatten' the Alpha channel.

			VB Code
			
			Imports System.ComponentModel
Imports System.Runtime.InteropServices

<DllImport("comctl32.dll")> _
Private Shared Function ImageList_GetIcon(ByVal himl As IntPtr, ByVal i As Int32, ByVal diFlags As Int32) As IntPtr
End Function

<DllImport("user32.dll")> _
Private Shared Function DestroyIcon(ByVal hIcon As IntPtr) As Boolean
End Function

Private Sub ImageListDraw(ByVal imageList As ImageList, ByVal imageIndex As Int32, ByVal graphics As Graphics, ByVal location As Point)
    ImageListDraw(imageList, imageIndex, graphics, location, True, Color.Empty)
End Sub

Private Sub ImageListDraw(ByVal imageList As ImageList, ByVal imageIndex As Int32, ByVal graphics As Graphics, ByVal location As Point, ByVal enabled As Boolean, ByVal backColor As Color)

    If imageIndex > imageList.Images.Count - 1 OrElse imageIndex < 0 Then Return

    Dim hIco As IntPtr = ImageList_GetIcon(imageList.Handle, imageIndex, 0)
    Dim ico As Icon = Icon.FromHandle(hIco)
    Dim bmp As Bitmap = IconToAlphaBitmap(ico)

    If enabled Then
        graphics.DrawImage(bmp, location.X, location.Y)
    Else
        ControlPaint.DrawImageDisabled(graphics, bmp, location.X, location.Y, backColor)
    End If

    DestroyIcon(hIco)
    ico.Dispose()
    bmp.Dispose()

End Sub      
			
C# Code
			
			using System.Runtime.InteropServices;


[DllImport("comctl32.dll")]
private static extern IntPtr ImageList_GetIcon(IntPtr himl, int i, int diFlags);

[DllImport("user32.dll")]
private static extern bool DestroyIcon(IntPtr hIcon);
        
private void ImageListDraw(ImageList imageList, int imageIndex, Graphics graphics, Point location)
{
    ImageListDraw(imageList, imageIndex, graphics, location, true, Color.Empty);
}
        
private void ImageListDraw(ImageList imageList, int imageIndex, Graphics graphics, Point location, bool enabled, Color backColor)
{
    if (imageIndex > imageList.Images.Count - 1 || imageIndex < 0) return;
            
    IntPtr hIco = ImageList_GetIcon(imageList.Handle, imageIndex, 0);
    Icon ico= Icon.FromHandle(hIco);
    Bitmap bmp = IconToAlphaBitmap(ico);
            
    if (enabled)
        graphics.DrawImage(bmp, location.X, location.Y);
    else
        ControlPaint.DrawImageDisabled(graphics, bmp, location.X, location.Y, backColor);
            
    DestroyIcon(hIco);
    ico.Dispose();
    bmp.Dispose();

}
			
			

			

You'll also need the IconToAlphaBitmap() method shown above(Get Alpha Bitmap from 32 bit Icon.)