控件的Invalidate()与Paint事件怎么联系在一起的呢？

Question

以控件PictureBox为例
我知道调用Invalidate()后，就会产生一个Paint消息，Form就会重画但是在.net compact framework里面picturebox控件只有Invalidate，没有Paint。
有Invalidate，可以理解为Picturebox在调用invalidate会向系统产生重画消息，但这个重画却不是由Paint完成的（因为.net cf中没有Paint事件）？？
我自己写了一个myPicturebox控件（从.net自己的picturebox继承过来的），并添加了Paint事件，但是我在写了myPicturebox1.Invalidate()语句后，系统根本没有调用我的Paint事件...那么如何把系统的Invalidate和我添加的Paint事件联系起来呢？

Answer 1

[Docking(DockingBehavior.Ask), ComVisible(true), DefaultBindingProperty("Image"), Designer("System.Windows.Forms.Design.PictureBoxDesigner, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"), DefaultProperty("Image"), SRDescription("DescriptionPictureBox"), ClassInterface(ClassInterfaceType.AutoDispatch)]
public class PictureBox : Control, ISupportInitialize
{
    // Fields
    private BorderStyle borderStyle;
    private int contentLength;
    private AsyncOperation currentAsyncLoadOperation;
    private bool currentlyAnimating;
    private Image defaultErrorImage;
    [ThreadStatic]
    private static Image defaultErrorImageForThread;
    private static readonly object defaultErrorImageKey;
    private Image defaultInitialImage;
    [ThreadStatic]
    private static Image defaultInitialImageForThread;
    private static readonly object defaultInitialImageKey;
    private Image errorImage;
    private static readonly object EVENT_SIZEMODECHANGED;
    private bool handleValid;
    private Image image;
    private ImageInstallationType imageInstallationType;
    private string imageLocation;
    private Image initialImage;
    private object internalSyncObject;
    private SendOrPostCallback loadCompletedDelegate;
    private static readonly object loadCompletedKey;
    private static readonly object loadProgressChangedKey;
    private SendOrPostCallback loadProgressDelegate;
    private BitVector32 pictureBoxState;
    private const int PICTUREBOXSTATE_asyncOperationInProgress = 1;
    private const int PICTUREBOXSTATE_cancellationPending = 2;
    private const int PICTUREBOXSTATE_inInitialization = 0x40;
    private const int PICTUREBOXSTATE_needToLoadImageLocation = 0x20;
    private const int PICTUREBOXSTATE_useDefaultErrorImage = 8;
    private const int PICTUREBOXSTATE_useDefaultInitialImage = 4;
    private const int PICTUREBOXSTATE_waitOnLoad = 0x10;
    private const int readBlockSize = 0x1000;
    private byte[] readBuffer;
    private Size savedSize;
    private PictureBoxSizeMode sizeMode;
    private MemoryStream tempDownloadStream;
    private int totalBytesRead;    // Events
    [EditorBrowsable(EditorBrowsableState.Never), Browsable(false)]
    public event EventHandler CausesValidationChanged;
    [EditorBrowsable(EditorBrowsableState.Never), Browsable(false)]
    public event EventHandler Enter;
    [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
    public event EventHandler FontChanged;
    [EditorBrowsable(EditorBrowsableState.Never), Browsable(false)]
    public event EventHandler ForeColorChanged;
    [EditorBrowsable(EditorBrowsableState.Never), Browsable(false)]
    public event EventHandler ImeModeChanged;
    [EditorBrowsable(EditorBrowsableState.Never), Browsable(false)]
    public event KeyEventHandler KeyDown;
    [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
    public event KeyPressEventHandler KeyPress;
    [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
    public event KeyEventHandler KeyUp;
    [EditorBrowsable(EditorBrowsableState.Never), Browsable(false)]
    public event EventHandler Leave;
    [SRCategory("CatAsynchronous"), SRDescription("PictureBoxLoadCompletedDescr")]
    public event AsyncCompletedEventHandler LoadCompleted;
    [SRCategory("CatAsynchronous"), SRDescription("PictureBoxLoadProgressChangedDescr")]
    public event ProgressChangedEventHandler LoadProgressChanged;
    [EditorBrowsable(EditorBrowsableState.Never), Browsable(false)]
    public event EventHandler RightToLeftChanged;
    [SRDescription("PictureBoxOnSizeModeChangedDescr"), SRCategory("CatPropertyChanged")]
    public event EventHandler SizeModeChanged;
    [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
    public event EventHandler TabIndexChanged;
    [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
    public event EventHandler TabStopChanged;
    [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
    public event EventHandler TextChanged;    // Methods
    static PictureBox();
    public PictureBox();
    private void AdjustSize();
    private void Animate();
    private void Animate(bool animate);
    private void BeginGetResponseDelegate(object arg);
    private Uri CalculateUri(string path);
    [SRDescription("PictureBoxCancelAsyncDescr"), SRCategory("CatAsynchronous")]
    public void CancelAsync();
    protected override void Dispose(bool disposing);
    internal override Size GetPreferredSizeCore(Size proposedSize);
    private void GetResponseCallback(IAsyncResult result);
    private Rectangle ImageRectangleFromSizeMode(PictureBoxSizeMode mode);
    private void InstallNewImage(Image value, ImageInstallationType installationType);
    [SRCategory("CatAsynchronous"), SRDescription("PictureBoxLoad0Descr")]
    public void Load();
    [SRCategory("CatAsynchronous"), SRDescription("PictureBoxLoad1Descr")]
    public void Load(string url);
    [SRDescription("PictureBoxLoadAsync0Descr"), SRCategory("CatAsynchronous")]
    public void LoadAsync();
    [SRDescription("PictureBoxLoadAsync1Descr"), SRCategory("CatAsynchronous")]
    public void LoadAsync(string url);
    private void LoadCompletedDelegate(object arg);
    private void LoadProgressDelegate(object arg);
    protected override void OnEnabledChanged(EventArgs e);
    private void OnFrameChanged(object o, EventArgs e);
    [EditorBrowsable(EditorBrowsableState.Advanced)]
    protected override void OnHandleCreated(EventArgs e);
    [EditorBrowsable(EditorBrowsableState.Advanced)]
    protected override void OnHandleDestroyed(EventArgs e);
    protected virtual void OnLoadCompleted(AsyncCompletedEventArgs e);
    protected virtual void OnLoadProgressChanged(ProgressChangedEventArgs e);
    protected override void OnPaint(PaintEventArgs pe);

Answer 2

protected override void OnPaint(PaintEventArgs pe)
{
    if (this.pictureBoxState[0x20])
    {
        try
        {
            if (this.WaitOnLoad)
            {
                this.Load();
            }
            else
            {
                this.LoadAsync();
            }
        }
        catch (Exception exception)
        {
            if (ClientUtils.IsCriticalException(exception))
            {
                throw;
            }
            this.image = this.ErrorImage;
        }
    }
    if (this.image != null)
    {
        this.Animate();
        ImageAnimator.UpdateFrames();
        Rectangle rect = (this.imageInstallationType == ImageInstallationType.ErrorOrInitial) ? this.ImageRectangleFromSizeMode(PictureBoxSizeMode.CenterImage) : this.ImageRectangle;
        pe.Graphics.DrawImage(this.image, rect);
    }
    base.OnPaint(pe);
}