首先从这里下载：Download the ExtensibleDialogsSource.msi sample file (297 KB).
原文链接：Extend the Common Dialog Boxes Using Windows Forms 1.x
下载后安装，然后打开项目文件，将OpenFileDialog.cs文件中的内容替换如下：
/*================================================================================
File: OpenFileDialog.cs
Summary: This is part of a sample showing how to place Windows Forms controls
inside one of the common file dialogs.
----------------------------------------------------------------------------------
Copyright (C) Microsoft Corporation. All rights reserved.
This source code is intended only as a supplement to Microsoft Development Tools
and/or on-line documentation. See these other materials for detailed information
regarding Microsoft code samples.
This sample is not intended for production use. Code and policy for a production
application must be developed to meet the specific data and security requirements
of the application.
THIS CODE AND INFORMATION ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
================================================================================*/
using System;
using System.Text;
using System.Runtime.InteropServices;
using System.Drawing;
namespace ExtensibleDialogs
{
/// <summary>
/// The extensible OpenFileDialog
/// </summary>
public class OpenFileDialog : IDisposable
{
// The maximum number of characters permitted in a path
private const int _MAX_PATH = 260;
// The "control ID" of the content window inside the OpenFileDialog
// See the accompanying article to learn how I discovered it
private const int _CONTENT_PANEL_ID = 0x0461;
// A constant that determines the spacing between panels inside the OpenFileDialog
private const int _PANEL_GAP_FACTOR = 3;
/// <summary>
/// Clients can implement handlers of this type to catch "selection changed" events
/// </summary>
public delegate void SelectionChangedHandler( string path );
/// <summary>
/// This event is fired whenever the user selects an item in the dialog
/// </summary>
public event SelectionChangedHandler SelectionChanged;
// unmanaged memory buffers to hold the file name (with and without full path)
private IntPtr _fileNameBuffer;
private IntPtr _fileTitleBuffer;
// the OPENFILENAME structure, used to control the appearance and behaviour of the OpenFileDialog
private OpenFileName _ofn;
// user-supplied control that gets placed inside the OpenFileDialog
private System.Windows.Forms.Control _userControl;
// unmanaged memory buffer that holds the Win32 dialog template
private IntPtr _ipTemplate;
/// <summary>
/// Sets up the data structures necessary to display the OpenFileDialog
/// </summary>
/// <param name="defaultExtension">The file extension to use if the user doesn't specify one (no "." required)</param>
/// <param name="fileName">You can specify a filename to appear in the dialog, although the user can change it</param>
/// <param name="filter">See the documentation for the OPENFILENAME structure for a description of filter strings</param>
/// <param name="userPanel">Any Windows Forms control, it will be placed inside the OpenFileDialog</param>
public OpenFileDialog( string defaultExtension, string fileName, string filter, System.Windows.Forms.Control userControl )
{
// Need two buffers in unmanaged memory to hold the filename
// Note: the multiplication by 2 is to allow for Unicode (16-bit) characters
_fileNameBuffer = Marshal.AllocCoTaskMem( 2 * _MAX_PATH );
_fileTitleBuffer = Marshal.AllocCoTaskMem( 2 * _MAX_PATH );
// Zero these two buffers
byte[] zeroBuffer = new byte [2 * (_MAX_PATH+1)];
for( int i = 0; i < 2 * (_MAX_PATH+1); i++ ) zeroBuffer[i] = 0;
Marshal.Copy( zeroBuffer, 0, _fileNameBuffer, 2 * _MAX_PATH );
Marshal.Copy( zeroBuffer, 0, _fileTitleBuffer, 2 * _MAX_PATH );
// Create an in-memory Win32 dialog template; this will be a "child" window inside the FileOpenDialog
// We have no use for this child window, except that its presence allows us to capture events when
// the user interacts with the FileOpenDialog
_ipTemplate = BuildDialogTemplate();
// Populate the OPENFILENAME structure
// The flags specified are the minimal set to get the appearance and behaviour we need
_ofn.lStructSize = Marshal.SizeOf( _ofn );
_ofn.lpstrFile = _fileNameBuffer;
_ofn.nMaxFile = _MAX_PATH;
_ofn.lpstrDefExt = Marshal.StringToCoTaskMemUni( defaultExtension );
_ofn.lpstrFileTitle = _fileTitleBuffer;
_ofn.nMaxFileTitle = _MAX_PATH;
_ofn.lpstrFilter = Marshal.StringToCoTaskMemUni( filter );
_ofn.Flags = OpenFileNameFlags.EnableHook | OpenFileNameFlags.EnableTemplateHandle | OpenFileNameFlags.EnableSizing | OpenFileNameFlags.Explorer;
_ofn.hInstance = _ipTemplate;
_ofn.lpfnHook = new OfnHookProc(MyHookProc);
// copy initial file name into unmanaged memory buffer
UnicodeEncoding ue = new UnicodeEncoding();
byte[] fileNameBytes = ue.GetBytes( fileName );
Marshal.Copy( fileNameBytes, 0, _fileNameBuffer, fileNameBytes.Length );
// keep a reference to the user-supplied control
_userControl = userControl;
}
/// <summary>
/// The finalizer will release the unmanaged memory, if I should forget to call Dispose
/// </summary>
~OpenFileDialog()
{
Dispose( false );
}
/// <summary>
/// Display the OpenFileDialog and allow user interaction
/// </summary>
/// <returns>true if the user clicked OK, false if they clicked cancel (or close)</returns>
public bool Show()
{
return NativeMethods.GetOpenFileName( ref _ofn );
}
/// <summary>
/// Builds an in-memory Win32 dialog template. See documentation for DLGTEMPLATE.
/// </summary>
/// <returns>a pointer to an unmanaged memory buffer containing the dialog template</returns>
private IntPtr BuildDialogTemplate()
{
// We must place this child window inside the standard FileOpenDialog in order to get any
// notifications sent to our hook procedure. Also, this child window must contain at least
// one control. We make no direct use of the child window, or its control.
// Set up the contents of the DLGTEMPLATE
DlgTemplate template = new DlgTemplate();
// Allocate some unmanaged memory for the template structure, and copy it in
IntPtr ipTemplate = Marshal.AllocCoTaskMem( Marshal.SizeOf(template) );
Marshal.StructureToPtr( template, ipTemplate, true );
return ipTemplate;
}
/// <summary>
/// The hook procedure for window messages generated by the FileOpenDialog
/// </summary>
/// <param name="hWnd">the handle of the window at which this message is targeted</param>
/// <param name="msg">the message identifier</param>
/// <param name="wParam">message-specific parameter data</param>
/// <param name="lParam">mess-specific parameter data</param>
/// <returns></returns>
public IntPtr MyHookProc( IntPtr hWnd, UInt16 msg, Int32 wParam, Int32 lParam )
{
if (hWnd == IntPtr.Zero)
return IntPtr.Zero;
// Behaviour is dependant on the message received
switch( msg )
{
// We're not interested in every possible message; just return a NULL for those we don't care about
default:
{
return IntPtr.Zero;
}
// WM_INITDIALOG - at this point the OpenFileDialog exists, so we pull the user-supplied control
// into the FileOpenDialog now, using the SetParent API.
case WindowMessage.InitDialog:
{
IntPtr hWndParent = NativeMethods.GetParent( hWnd );
NativeMethods.SetParent( _userControl.Handle, hWndParent );
return IntPtr.Zero;
}
// WM_SIZE - the OpenFileDialog has been resized, so we'll resize the content and user-supplied
// panel to fit nicely
case WindowMessage.Size:
{
FindAndResizePanels( hWnd );
return IntPtr.Zero;
}
// WM_NOTIFY - we're only interested in the CDN_SELCHANGE notification message:
// we grab the currently-selected filename and fire our event
case WindowMessage.Notify:
{
IntPtr ipNotify = new IntPtr( lParam );
OfNotify ofNot = (OfNotify)Marshal.PtrToStructure( ipNotify, typeof(OfNotify) );
UInt16 code = ofNot.hdr.code;
if( code == CommonDlgNotification.SelChange )
{
// This is the first time we can rely on the presence of the content panel
// Resize the content and user-supplied panels to fit nicely
FindAndResizePanels( hWnd );
// get the newly-selected path
IntPtr hWndParent = NativeMethods.GetParent( hWnd );
StringBuilder pathBuffer = new StringBuilder(_MAX_PATH);
UInt32 ret = NativeMethods.SendMessage( hWndParent, CommonDlgMessage.GetFilePath, _MAX_PATH, pathBuffer );
string path = pathBuffer.ToString();
// copy the string into the path buffer
UnicodeEncoding ue = new UnicodeEncoding();
byte[] pathBytes = ue.GetBytes( path );
Marshal.Copy( pathBytes, 0, _fileNameBuffer, pathBytes.Length );
// fire selection-changed event
if( SelectionChanged != null ) SelectionChanged( path );
}
return IntPtr.Zero;
}
}
}
/// <summary>
/// Layout the content of the OpenFileDialog, according to the overall size of the dialog
/// </summary>
/// <param name="hWnd">handle of window that received the WM_SIZE message</param>
private void FindAndResizePanels( IntPtr hWnd )
{
// The FileOpenDialog is actually of the parent of the specified window
IntPtr hWndParent = NativeMethods.GetParent( hWnd );
// The "content" window is the one that displays the filenames, tiles, etc.
// The _CONTENT_PANEL_ID is a magic number - see the accompanying text to learn
// how I discovered it.
IntPtr hWndContent = NativeMethods.GetDlgItem( hWndParent, _CONTENT_PANEL_ID );
Rectangle rcClient = new Rectangle( 0, 0, 0, 0 );
Rectangle rcContent = new Rectangle( 0, 0, 0, 0 );
// Get client rectangle of dialog
RECT rcTemp = new RECT();
NativeMethods.GetClientRect( hWndParent, ref rcTemp );
rcClient.X = rcTemp.left;
rcClient.Y = rcTemp.top;
rcClient.Width = rcTemp.right - rcTemp.left;
rcClient.Height = rcTemp.bottom - rcTemp.top;
// The content window may not be present when the dialog first appears
if( hWndContent != IntPtr.Zero )
{
// Find the dimensions of the content panel
RECT rc = new RECT();
NativeMethods.GetWindowRect( hWndContent, ref rc );
// Translate these dimensions into the dialog's coordinate system
POINT topLeft;
topLeft.X = rc.left;
topLeft.Y = rc.top;
NativeMethods.ScreenToClient( hWndParent, ref topLeft );
POINT bottomRight;
bottomRight.X = rc.right;
bottomRight.Y = rc.bottom;
NativeMethods.ScreenToClient( hWndParent, ref bottomRight );
rcContent.X = topLeft.X;
rcContent.Width = bottomRight.X - topLeft.X;
rcContent.Y = topLeft.Y;
rcContent.Height = bottomRight.Y - topLeft.Y;
// Shrink content panel's width
int width = rcClient.Right - rcContent.Left;
rcContent.Width = (int)(width * 1.0 /1.6) + _PANEL_GAP_FACTOR;
NativeMethods.MoveWindow( hWndContent, rcContent.Left, rcContent.Top, rcContent.Width, rcContent.Height, true );
}
// Position the user-supplied control alongside the content panel
Rectangle rcUser = new Rectangle( rcContent.Right + (2 * _PANEL_GAP_FACTOR), rcContent.Top, rcClient.Right - rcContent.Right - (3 * _PANEL_GAP_FACTOR), rcContent.Bottom - rcContent.Top );
NativeMethods.MoveWindow( _userControl.Handle, rcUser.X, rcUser.Y, rcUser.Width, rcUser.Height, true );
}
/// <summary>
/// returns the path currently selected by the user inside the OpenFileDialog
/// </summary>
public string SelectedPath
{
get
{
return Marshal.PtrToStringUni( _fileNameBuffer );
}
}
#region IDisposable Members
public void Dispose()
{
Dispose( true );
}
/// <summary>
/// Free any unamanged memory used by this instance of OpenFileDialog
/// </summary>
/// <param name="disposing">true if called by Dispose, false otherwise</param>
public void Dispose( bool disposing )
{
if( disposing )
{
GC.SuppressFinalize( this );
}
Marshal.FreeCoTaskMem( _fileNameBuffer );
Marshal.FreeCoTaskMem( _fileTitleBuffer );
Marshal.FreeCoTaskMem( _ipTemplate );
}
#endregion
}
}
MainForm.cs中修改一下：
private void button1_Click(object sender, System.EventArgs e)事件和private void ofd_SelectionChanged( string path ),代码如下：
/// <summary>
/// Creates and shows an instance of the extended OpenFileDialog, with a PictureBox control placed inside
/// </summary>
private void button1_Click(object sender, System.EventArgs e)
{
// Create panel for the "preview" part of the dialog
Panel p = new Panel();
p.BorderStyle = BorderStyle.None;
// Add a picture box to the "preview" panel
_picBox = new PictureBox();
p.Controls.Add( _picBox );
_picBox.Dock = DockStyle.Fill;
_picBox.SizeMode = PictureBoxSizeMode.StretchImage;
_picBox.Click += new EventHandler( picBox_Click );
// Create and show the OpenFile Dialog
ExtensibleDialogs.OpenFileDialog ofd = new ExtensibleDialogs.OpenFileDialog( "jpg", "", "Picture files (*.JPG;*.GIF;*.PNG;*.tif)\0*.jpg;*.gif;*.png;*.tif\0\0", p );
ofd.SelectionChanged += new ExtensibleDialogs.OpenFileDialog.SelectionChangedHandler(ofd_SelectionChanged);
bool f = ofd.Show();
string s = ofd.SelectedPath;
if(s != string.Empty)
{
MessageBox.Show("You selected a photo, the file name is:\n" + s);
}
}
/// <summary>
/// Event handler that is called when the user clicks on a file or folder inside the dialog
/// </summary>
/// <param name="path">the full path of the currently-selected file</param>
private void ofd_SelectionChanged( string path )
{
// Check the path points to something valid before trying to display the contents
if( !File.Exists( path ) ) return;
if( !Path.HasExtension( path ) ) return;
string ext = Path.GetExtension( path ).ToLower();
if( ext == ".jpg" || ext == ".gif" || ext == ".png" || ext == ".tif" )
{
Image originalImage = new Bitmap(path);
int widthOriginal = originalImage.Width;
int heightOriginal = originalImage.Height;
int boxW = _picBox.Width;
int boxH = _picBox.Height;
Bitmap newBmp = new Bitmap(boxW, boxH);
Graphics g = Graphics.FromImage(newBmp);
float zoom = Math.Min((float)boxW / (originalImage.Width + 1), (float) boxH / (originalImage.Height + 1));
Rectangle destRect = new Rectangle(
(boxW - (int)(originalImage.Width * zoom))/2, (boxH - (int)(originalImage.Height * zoom))/2,
(int)(originalImage.Width * zoom), (int)(originalImage.Height * zoom));
Rectangle srcRect = new Rectangle(0, 0, originalImage.Width, originalImage.Height);
g.DrawImage(originalImage, destRect, srcRect, GraphicsUnit.Pixel);
_picBox.Image = newBmp;
g.Dispose();
originalImage.Dispose();
}
}
运行它，是不是比以前更方便和漂亮了点？
运行时截图：
主要的改进是修正了：
1、MSDN上的示例运行时图形区域太大，文件选择区域太小的问题。
2、修改了图像显示缩略图不成比例的问题。
美中不足:
(1)当选择好图片之后，如果点击“取消”，仍会弹出已选择的文件名。BUG！
(2)由于本人对C++不熟悉，无法调整弹出对话框的默认大小，目前好象只有560*340左右大小，哪位知道如何调整默认对话框尺寸，烦请告知为谢。
MSN：a3news#hotmail.com
